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[02

University of California Publications

JOOLOGY

VOLUME XVIII
LOLs) = ATO

WITH 20 PLATES

EDITORS
WILLIAM EMERSON RITTER
CHARLES ATWOOD KOFOID

GARI 1921
DA (48S

UNIVERSITY OF CALIFORNIA PRESS
BERKELEY, CALIFORNIA

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18.

CONTENTS

. Mitosis in Giardia microti, by William C. Boeck; with plate 1; 1

TNO REN SBT Sc Ree ee Ry of A On eee

. An Unusual Extension of the Distribution of the Shipworm in San

Francisco Bay, California, by Albert LL. Barrows ........-...--------------

. Description of Some New Species of Polynoidae from the Coast of

California, by Christine Essenberg; with plates 2-3 -.................-...

. New Species of Amphinomidae from the Pacific Coast, by Christine

HS SOMITE TOF VRE MOLEC CS 0) acc actensa ene caus ee eee recs cata chase erence

. Crithidia euryophthalmi, sp. nov. from the Hemipteran Bug, Hury-

ophthalmus convivus Stal, by Irene McCulloch; with 35 text
TOURS ete aces cect sce cen essa e so ae fee ae nee ee cece cena ee ck seonecucseeteeseeeeeeee

. On the Orientation of Hrythropsis, by Charles Atwood Kofoid and

Olivier Swe zy walic helo tonne seins Ge xt eeeeeeeese eee eee oe.

. The Transmission of Nervous Impulses in Relation to Locomotion

in the Harthworm, by John F. Bovard; with 4 figures TAL LER cence

. The Function of the Giant Fibers in Earthworms, by John F.

ATS Oyicbicclls mawysit laa lent FUG Gy ra GO Keb eee eee eee ee ee ee ee ae 2

. A Rapid Method for the Detection of Protozoan Cysts in Mam-

malraneBaeces, toy: Wallliam Cy Woe Ce state sss eee ec co. --c gee

. The Musculature of Heptanchus maculatus, by Pirie Davidson; with

WAS RUNES, Aa GORI a aaa oe ae coe tae scence cect coe cecmse near eattnceas ci enense sc aedeeueeeeedaan

. The Factors Controlling the Distribution of the Polynoidae of the

Pacific Coast of North America, by Christine Essenberg; with
DUN STYa is @ eye) arpa alfa g hale) Shas i Sp. < res eee ee eae ae Aa Er a Sa
Differentials in Behavior of the Two Generations of Salpa demo-
cratica Relative to the Temperature of the Sea, by Ellis L.
Michvelsswith plates Ooi s I nenume am tet 22: sc 8e eee eee eee

. A Quantitative Analysis of the Molluscan Fauna of San Francisco

Bay, by E. L. Packard; with plates 12-13; 6 figures in text -.......

. The Neurometer Apparatus of Huplotes patella, by Harry B. Yocom;

Ap VAOE) oly OWES eS a Leet pa eee et RL ra ara ER ee eee

. The Significance of Skeletal Variations in the Genus Peridinium,

by A. L. Barrows; with plates 17—20; 19 figures in text .................-

. The Subclavian Vein and Its Relations in Elasmobranch Fishes,

Loy? do Intreialie Weeraneils (By tlre ness Tl HES eee ete Sacer cooeee doce eee eer

. The Cerearia of the Japanese Blood Fluke Schistosoma japonicum

Katsurada, by William W. Cort; 3 figures in text -...-....--..-------------
Notes on the Eggs and Miracidia of the Human Schistosomes, by
wy Tle, NAV CCKanRR Cf MNS AUREIS) AY UEDA eae el ee eer ee

PAGES

27-43

45-60

61-74

103-134

135-144

145-149

151-170

171—238

239-298

299-336

337-396

397-478

479-484

485-507

509-519

HT ra emcee Suet ee NR Sh 2s a a sk 521-529

ary ~
~"-SRSBi lL

INDEX*

Acanthias, 168.
vulgaris, 152, 157.

Adinida, 404, 405.

Alaska, 175, 400.

‘« Albatross,’’ U.S.S., expeditions, 172,
400; survey of San Francisco
Bay, 299, 312, 313.

Allolobophora foetida, 106, 137.

Amphinomidae from the Pacific
Coast, New Species of, 61;
classification, 62; habitat, 63;

bathymetrical distribution, 63;
description of new species, 63-69.

Amphinomina, subfamily, 62.

Amphitrite, 213, 216.

Annelids, distribution of, 171, 172;
Polynoidae, scaly annelids, 174;
defensive organs of, 211; blind-
ness of, 222, 223.

Antinoé anoculata, 183.

Aphrodita aculeata, 209.

Aphroditidae and Polynoidae, resem-
blance between, 46.

Arenicola, 127.

Arnold, A. F., quoted, 284.

Asterias ochracea, 213, 220.

trochelii, 220.

Atkinson, E. L., cited, 487.

Autotomy in earthworms, 111.

Banyuls-sur-Mer, France, 97.

Barrows, A. L., 27, 397.

Bartsch P., acknowledgment to, 30.

Bergh, R. S., cited, 411.

Biedermann, W., studies on locomo-
tion of earthworms, 105, 106,
119; 129, 130, 136.

Bispira polymorpha, 127.

““Blake,’’ U.S. Survey Steamer, ex-
peditions, 172.

Blanfordia, 487.

nosophora, 487, 489.

Blastodinium, 405.

Blood fluke, Egyptian, 485; Japanese,
485, 486. See also Schistosoma
haematobium; 8S. japonicum.

Boeck, W. C., 1, 145.

Bovard, J. F., 103, 1385; acknowledg-
ment to, 400.

Braune, cited, 380.

Brock, H., cited, 407.

Budington, R. A., cited, 120, 121.

Bullinus contortus, 488.

dybowski, 488.

Burrage, G. H., U.S. N., member of
board for survey of San Francisco
Bay, 299.

* Univ. Calif. Publ. Zool., vol. 18.

[521]

Biitschli, O., 96; cited, 378.

California, 63, 489. :

Calkins, G. N., cited, 370, 371.

Calonympha, genus, 383.

Carchesium genus, 350.

polypinum, 380.

Cardium corbis, 303, 304, 307, 308,
312, 315, 320, 321, 322.

Carlson, A. J., cited, 122, 127.

Carquinez Strait, 315.

Carter, H. F., cited, 145.

Cawston, F. G., 488.

Centrodinium, genus, 416.

Ceratium, genus, 403, 416, 417.

furea, figures of, 92, 93.
gravidum, 91, figures of, 90.

Ceratocorys, genus, 440.

Cercaria of the Japanese Blood

Fluke, Schistosoma japonicum

Katsurada, 485; development of,

in Katayama snail, 487; intro-

duced into mice, 487; material
studied, 490; method of study,

490; agreement with cercariae

of other species, 491; structure

of, 492-496, figures showing, 493,

497; excretory system, 494, fig-

ure showing, 499; oral sucker

and cephalic glands, 496-501;

activity of, 502-504.

Cerearia blanchardi, 488, 489.

Cereariae of human _ schistosomes,
491.

Cerebratulus, 127.

Cette, Biological Station, 400, 448.

““Challenger’’ expedition, 172.

Chemical composition of water, fac-
tor in distribution of Poly-
noidae, 209.

Chesapeake Bay, shipworms in, 37,
38; temperature of, compared
with that of San Francisco Bay,
38.

Child, C. M., cited, 371, 372, 421, 463.

Chilodon, genus, 380.

Chione undatella, 308.

Chitin, or lime salts, effect of secre-
tion of, on animal’s habitat, 210.

Chloeia pinnata, 63.

Christiansen, E. B., 1, 21; cited, 366,
382.

Christineberg, in the Skagerak, 448.

Clam farming industry, 314, 315.

Claparéde, D., cited, 172.

Clark, A. H., cited, 191, 209.

Index

Cocaine, effect of on nerve cord of
earthworms, 143.

Coceudina keromina, 338.

Cochlodinium citron, 93, 94.

pulchellum, 91.

Cockerell, F. D. A., cited, 205.

‘*Cold islands,’’ 198.

Coleps, genus, 380.

Columbella gausapata, 303, 320, 321.

Commensal polynoids, 213, 216; ad-
vantages of, 219, 220; plasticity
in, 224; adaptive variation in
setae of, 224; variation in color,
225, 226; external changes, 227.

Conor, A., cited, 509.

Coreus marginatus, 79.

Cort, W. W., 485, 509.

Crepidula nivea, 303, 307, 320, 321.

Crithidia euryopthalmi, sp. nov., from
the Hemipteran Bug, Lury-
opthalmus convivus Stal, 75.

Crithidia euryopthalmi, compared
with C. lepticoridis, 76; infec-
tion of Euryopthalmus convivus
by, 81, 83, 85, 87; life eycle,
82; infective and degenerative
cycles, 87.

lepticoridis compared with C. eury-
opthalmi, 76.

Crockett, California, 30. :

Cropper, J. W., cited, 145, 148.

Coyptochiton stelleri, 213.

Cysts in Giardia microti, 20, 23.

Cytoplasmic structures and changes,
correlation of mitosis with, 18.

Daday, E., cited, 91, 92.

Daniel, J. F., 479.

Daboux, J. G., cited, 224.

Da Silva, M. P., cited, 488.

Davidson, Pirie, 151.

Dechant, E., cited, 129, 130.

Degenerative cycles in Euryopthal-
mus convivus, 87.

Delage, Y., cited, 96.

Diatoms, influence of temperature
on, 200.

Delitzsch, Saxony, 401.

Didinium, genus, 381.

nasutum, 380, 384.

Differentials in Behavior of the Two
Generations of Salpa democrat-
ica Relative to the Temperature
of the Sea, 239.

Dinifera, 404, 458.

Dinoflagellata, morphology of, 89;
Hryopthropsis admitted to, 96;
relationship and morphology of,
400; habitat, 401; flagella of,
401; shell of, 402; protoplasm
of, 403; asymmetry in, 403, 462;
horns or spines in, 403.

Dinophysidae, 404, 405, 458.

Dinophysis, 405.

Diplodinium ecaudatum, 365, 366,
378, 379, 380, 381, 383, 384, 385.

Dufour, L., cited, 79.

Earthworm, description of locomo-
tion in, 104-105; function of the
nerve cord, 104, 105-106; effect
of anesthetizing, 107-108, 109;
tension, in etherized worms, 109,
in locomotion, 112-118; locomo-
tor impulses, limits of transmis-
sion, 118-122, rates of transmis-
sion, 122-125; giant fiber im-
pulses, 125-128.

Earthworm, The Transmission of
Nervous Impulses in Relation to
Locomotion in, 103.

Earthworms, Function of Giant
Fibers in, 135; theories regard-
ing, 136; functions of the nerve
cord, 136; experiments in tran-
section of nerve cord, 137-138,
in regeneration of, 138-142, in
removal of, 140-142, with sto-
vaine, 143; summary, 144.

Eetoparasitic polynoidae, 224.

Egyptian blood fluke, 485. See also
Schistosoma haematobium.

Ehlers, E., cited, 62, 172, 204, 206.

Ehrenberg, C. G., cited, 338, 401.

Elasmobranch Fishes, Subclavian
Vein in, and Its Relations, 479;
material studied, 479; method,
480; observations on material
studied, 481-482; discussion, 483.

Engelmann, I. W., cited, 356, 378,
380.

Entamoeba, 145.

Environment, effect of, on animal
life, 173, 215, 216.

Enzymes, 226.

Epitonium hindsi, 303, 307, 320, 322.

savinae, 303, 307, 320.

Erythropsis, orientation of, 89, 92;
transverse flagellum of, 93; ocel-
lus, 94; prod (tentacle), 94;
prod (tentacle), 94; girdle, 96;
paradinial lines, 97; attachment
area, 99.

agilis, 95; figures of, 98.

cornuta, figure of, 98.
Essenberg, Christine, 45, 171.
Eunoé, genus, 212.

barbata, 47.

eaeca, 183.

Euperidinium, genus, 411.

Euphrosinidae, 62.

Euphrosyne aurantiaca, 64, 65.

calypta, 63-65; figures showing,
opp. 72.

dumosa, 69.

kyllosetosa, 63, 68-69.

limbata, 69.

Index

multibranchiata, 63, 65-66; fig-
ures showing, opp. 72.

pacifica, 67.

spirocirrata, 63, 66-68; figures

showing, opp. 72, 74.

Euphrosynina, subfamily, 62, 63.

Euploea, genus, 338.

Euplotes, genus, 338, 339-340.

charon, 338.

harpa, 338, 340, 356, 378, 381.

longipes, 338.

patella, 338; preparation of for
study, 341-343; illustrations of,

opp. 392, 394, 396.

Structure, external features,
344; diverticulum, 347; ecto-
plasm, 348; endoplasm, 349;
food vacuoles, 349; contractile
vacuole, 350; nuclear strue-
ture, 350;° macronucleus, 350;
micronucleus, 351.

Motor organs and neuromotor
apparatus, 351; cirri, 352;
membranelles, 353; structure
of neuromotor apparatus, 354;
function of neuromotor organs,
359; figure showing, 356; evi-
dence of neural function, 362.

Binary fission, 367-368; forma-
tion of new eirri, 372, peri-
stome, 373, neuromotor appa-
ratus, 375.

Fibrillar system in other ciliates,
378; neuromotor apparatus of
flagellates, 381; homology of
neuromotor apparatus in eili-
ates and flagellates, 383.

vannus, 339.
worcesteri, 339, 340, 344, 349, 350,

352, 353, 356, 368, 372, 373, 374,

3fo, 378, 38.

Euplotes patella, Neuromotor Appa-
ratus of, 337; summary of con-
clusions, 3886; literature cited,
388.

Euryophthalmus convivus, 75; flagel-
lates infecting digestive tract,
76, 81, 83, 85, 87; morphology
of digestive tract, 78, figures
showing, 80.

Euryopthalmus convivus Stal, the
Hemipteran Bug, Crithidia eury-
opthalmi, sp. nov., from the, 75.

Eurythoé, genus, 63.

californica, 67.

Exuviaella, genera, 404.

Exuviation in Peridinium, 417.

Factors Controlling the Distribution
of the Polynoidae of the Pacific
Coast of North America, 171.

Falk, H. O., acknowledgment, 69.

Farallone, San Francisco Bay, 63.

Fauna, oceanic, feeding grounds of,
212.

Fauré-Fremiet, E., cited, 92, 93, 94,
96, 97, 98, 407, 412, 434, 459.

Fowler, G. H., quoted, 285.

France, 96.

Friedlander, B., work on the move-
ments of earthworms, 104, 105,
128, 130, 131, 136, 142.

Fujinami, A., cited, 486, 487;
acknowledgment to, 489.

Function of the Giant Fibers in
Earthworms, 135.

Fundulus, 214.

Gattyana amundseni, 203.

cirrosa, 203, 209.

senta, 206.

Gemma gemma var. purpura, 303,
320, 321.

Giardia, genus, 382.

intestinalis, 145; compared with G.
microti, 5.

Giardia microti, 1; infection of
hosts, 3; compared with G. muris,
3, 5; duodenum natural habitat
of, 3; pathogenicity of, 4; mor-
phology of, 4; morphological
structures, 5; parabasal bodies,
8, funetion of, 9; figures of, opp.
10, 26; neuromotor apparatus,
19; cysts, 20.

Mitosis in, 1; phases of, 11-17,
figures showing, opp. 10, 26; cor-
related with cytoplasmic struc-
tures and changes, 18; conclu-
sions, 22.

muris, 5.

Glyphis aspera, 213.

Goniodoma, genus, 416.

Gonyaulax, genus, 205, 402, 416, 420,
427, 438, 459. .

Goto, 8., acknowledgment to, 400.

Gran, H. H., cited, 411.

Grassi, B., and Schweiakoff, W., cited,
21

Griffin, L. E., cited, 344, 349, 350, 352,
353, 354, 356, 359, 367, 368, 370,
372, 374, 375, 378.

Grube, E., cited, 206.

Gymnodinidae, 404, 405.

Gymnodinioidae, 89, 91.

Gymnodinium, 405.

Halosydna californica, 183, 212.

carinata, 47, 212.
insignis, 175, 183, 212, 213, 216,
227; figures showing, 238.
interrupta, 183, 212.
lagunae, 47.
macrocephala, 48; description of,
53; comparison of, 54; occur-
rence, 55; plate showing, 60.
Hanee, R. T., cited, 370.
Haptomonads, 86.

Index

Harmothoé bonitensis, 48; compari-
son and description of, 48; oc-
currence of, 50; plate showing,
opp. 98.

earinata, 47.

erassicirrata, 47.

forcipata, 184, 206.

fragilis, 177.

hirsuta, 177, 183, 206, 211; figures
showing, 236, 238.

imbricata, 47, 174, 183, 211, 213.

johnsoni, 48; description of, 50;
comparison of, 52; occurrence
of, 53; plate showing, opp. 60.

lamellifera, 183. ~°

multisetosa, 183, 208, 204.

triannulata, 177.

luta, 177, 206.

yokohamiensis, 206.

Hashegawa, T., cited, 486.

Helodrilus caliginosa, 106, 137, 142;
experiments in anesthetizing, 106.

Hemipteran Bug, Huryopthalmus con-
vivus Stal, Crithidia euryopthal-
mi, sp. nov., from the, 75.

Heptanchus cinereus, 152, 147.

maculatus, description of, 151; fig-
ures of, 155, 158, 160, 163, 164,
168, 169; subclavian vein, fig-
ures of, 480, observations and
discussion of, 481-483.

Heptanchus maculatus, Musculature
of, 151; pharyngeal musculature,
152; superficial circular muscles,
153; interarcuales, 158; subspin-
alis, 159; adductors, 159; hypo-
branchials, 161; musculature asso-
ciated with organs of special
sense, 162; appendicular, 163;
of the trunk, 167.

‘Hérouard, E., cited, 96.

Hertwig, R., 94, 95.

Heterocapsa, genus, 416.

Heterodinium, genus, 416, 440, 445,
459.

Hexanchus, 165.

griseus, 152.

Hickey, J. P., acknowledgment, 509,
516.

Hickson, S. K., quoted, 284.

Hinnites giganteus, 303, 320, 321.

Hjort, J., cited, 202; quoted, 284.

Holeomb, R., cited, 516.

Holothuria californica, 220.

Holway, R. S., cited, 198.

Huffman, O. V., cited, 515.

Human schistosomes, method of trans-
mission, 486; value of study of,
489; characters of cercariae, 491.
See also Schistosoma, and its
species.

Human Schistosomes, Notes on. the
Eggs and Miracidia of, 509.

[524]

Hypotricha, 350, 353, 371.

Ikeno, 8., cited, 384.

Ilynassa obsoleta, 314.

Iturbe, J., 488.

Izuka, A., cited, 203.

Janicki, C., cited, 383.

Japan, 175.

Japanese blood fluke, 485, 486. See
also Cerearia of the Japanese
Blood Fluke; Schistosoma japon-
icum.

Japanese current, 208.

Japanese Islands, 203.

Jenkins, O. P., cited, 122, 127.

Joergersen, E., system of classifica-
tion of Peridinium, 412, 413-428,
460.

Johnson, H. P., cited, 45, 218, 220.

Johnstone, J., quoted, 283.

Katayama nosophora, 487.

Katsurada, F., cited, 486.

Kerona patella, 338.

Kodiak Island, Alaska, 66.

Kofoid, C. A., 89; acknowledgment,
2, 45, 61, 108, 173, 300, 400, 489;
cited, 1, 9, 21, 205, 330, 366, 340,
382, 383, 403, 405; member of
board for survey of San Fran-
cisco Bay, 299.

Konno, F. F., acknowledgment to,
488.

Krakow, Poland, 401.

Krawany, J., cited, 127.

Krukenberg, C. F. W., cited, 105.

Kuno Siwo, or Japanese current, 208.

La Jolla, California, 69, 99.

Langdon, F. E., cited, 129.

Lebour, M. V., cited, 91.

Leiper, R. T., cited, 487, 488, 489,
514.

Leodocidae, 63.

Lepidasthenia gigas, 177, 183, 213,

218, 223, 224, 228, 236.

Lepidonotus caeloris, 47, 175, 183,
203, 204.

squamatus, 174, 184, 215, 228; fig-
ures Showing, 236, 238.

Leptocoris trivittatus, 76, 79, 87.

Life zones on the Pacifie Coast, 75.

Light intensity, effect of on deep sea
animals, 223.

‘‘Lightning’’ expedition, 172.

Lime salts, 210.

Limnoria, crustacean woodbores, 28,
29.

Literature cited, 24, 43, 56, 70, 88,
101, 134, 144, 149, 170, 231, 291,
333, 388, 466, 484, 505, 519.

Loeb, J., cited, 210.

Looss, A., cited, 485, 486, 514, 518.

Lucapina crenulata, 220, 225.

Lumbriconereis, 127. —

Index

Lumbrinereidae, 62.
Lunatia duplicata, 314.
heros, 314.

Lupinus arboreus, 75.

Lutz, A., cited, 488, 489.

Lygaeus militaris, 79.

Lysidice, 221, 226.

McClung, C. E., cited, 370.

McCulloch, Irene, 75; cited, 383.

McEwen, G. F., acknowledgment to,
173, 191, 208; cited, 241.

McGlashan, H. D., acknowledgment
to, 32.

McIntosh, W. C., cited, 62, 63, 206,
209, 221, 227, 228.

Macoma balthica, 303, 304, 305, 307,

320, 322.

inquinata, 303, 304, 307, 320, 321,
322.

nasuta, 303, 304, 307, 312, 320, 321,
322.

Madeira Islands, 95.

Maier, H. N., cited, 353, 354, 357,
361, 378, 380.

Mangin, O., cited, 91, 450, 451.

Mare Island Navy Yard, California,
damage done at, by shipworms,
29.

Marenzeller, E., cited, 174, 206.

Massachusetts, Commissioners on Fish-
eries and Game, cited, 309; clam
industry in, 314.

Mastigophora, order, 400, 404.

Matsuura, U., cited, 486.

Matthews, J. R., cited, 145.

Maupas, E., cited, 353, 356, 378.

Maxwell, S. S., acknowledgment, 108.

Meadow mouse. See Microtus eali-
fornicus californicus.

Metaperidinium, 412, 413, 421, 428,
429, 430, 431, 4385, 438, 444, 445,
446, 447, 454, 460, 461.

Metschnikoff, E., 95.

Meunier, A., cited, 412.

Michael, E. L., 239; cited, 202, 282.

Microtus californicus californicus, 1;
gas inflation in, 4.

Mitosis in Giardia microti, 1; phases
of, 11, 16, 17, figures showing,
10, 26; correlated with cytoplas-
mie structures, 18; conclusions,
22.

Miyagawa, Y., cited, 486, 487, 491.

Miyairi, K., 486, 487; cited, 487.

Modiolus, ef. rectus, 303, 320, 321.

Molluscan Fauna of San Francisco
Bay, A Quantitative Analysis of,
299; collection of material, and
method of procedure, 300-301;
general distribution, 301; species
of, 303-308; economic consider-
ations, 308; factors governing
distribution, 317: depth, 318,

type of bottom, 318, salinity,
322, temperature, 324, food sup-
ply, 327, biotic environment, 330;
summary, 331.

Monaco, Oceanographic
400.

Monia macroschisma, 303, 320, 321.
Moore, J. P., acknowledgment, 47, 55,
172; cited, 206.
Murray, J., cited, 202,

quoted, 284.

Institute,

210, 215;

. Musculature of Heptanchus Macu-

[525]

latus, 151,
Mustelus, genus, 167, 168.
antareticus, 479, 481.
henlei, subclavian vein in, and its
relations, 481-483.

Mya arenaria, 303, 304, 306, 307, 308—
310, 311, 314, 315, 320, 321, 322,
Sail.

california, 303, 304, 307, 320, 322.
ealifornica, 322.
Mytilus californianus, 311, 315.
‘ealifornicus, 308, 311.
edulis, 308, 304, 305, 307, 308, 311,
313, 320, 321.

Naegleria gruberi, 381, 383.

Nakamura, H., cited, 486.

Nansen, F., cited, 198.

Naples, Zoological Station, 400, 448.

Narabayaski, F., cited, 486, 488.

Nassa fossata, 303, 307, 320, 322.

mendica, 303, 320, 321.
perpinguis, 303, 320, 322.
Nectomonads, 86.
Nereis, 127.
dumerilii, 207.
mirabilis, 207.

Neresheimer, E. R., cited, 378, 379.

Nervous Impulses, The Transmission
of, in Relation to Locomotion in
the Earthworm, 103; materials
and methods of study, 106-107;
statement of problem, 108; ex-
periments with anesthetized
worms, 108; free moving, 109;
tension factor, 109; anatomy,
111; free nerve preparations,
112-116; limits of transmission,
118; dependence on nervous sys-

tem, 120; locomotor impulses,
122; giant fiber impulses, 125;
the nervous mechanism, 128—

130; transmission by reinforced
stimuli, 131; summary, 132-133.
Neuromotor apparatus, first use of
term, 351, 378; parts of, 351;
definition of, 352; description of
motor parts, 352-354; structure
of, 354-359; ‘‘motorium,’’ 355,
359, 365, figure showing, 356;
function of, 359; evidence of

Index

neural function, 362; in flagel-
lates, 381; homology of, in cilia
and in flagellates, 383.

New International Encyclopaedia,
quoted, 284.

Ocean currents, 207.

Ocean depths, 215.

O’Donoghue, C. H., cited, 479, 483.

Odostomia franciseana, 303, 320, 321.

Ogata, 8., 488.

Oleum, California, 31.

Ophryodendron, 95.

Ophryoscolex purkyngei, 380.

Orientation of Hrythropsis, On
89.

Ornithocereus, genus, 405.

Orthoperidinium, subgenus, 412,
428, 431, 432, 433, 434, 435,
444, 446, 447, 452, 458, 460,

Ostrea elongata, 308, 311.

lurida, 303, 304, 306, 307, 308,
3116, 320) 321, 322:

Oxyrrhis, 405.

Pacifie coast, life zones on, 175.

Packard, H. L., 299.

Palmiridae, 62.

Panope generosa, 308, 312.

Paphia staminea, 303, 307, 308, 310,
313, 314, 315, 320, 322. -

Paramoecium bursaria, 341, 371.

Paraperidinium, subgenus, 413, 421,
428, 429, 433, 434, 435, 438, 444,
446, 449, 454, 458, 460, 461.

Parker, G. H., acknowledgment, 108.

Parker, T. J., cited, 479, 482, 483.

Pathogenicity of Giardia microti, 4.

Paulsen, O., cited, 412.

Pavillard, J., 96, 97; cited, 413.

Peeten, 312.

Perediniae, found at surface, 200.

Peridinidae, asymmetry in, 403, 443;
member of Dinifera, 404; char-
acters of, 405; skeletal variation
in genera of, 408, 435, 458;
major skeletal characters, 408—
414; plate development in genera
of, 416-419, 458; multiplication
of plates, 419-423; origin of
accessory plates, 439, of dorsal
plate patterns, 442. See also
Peridinium.

Peridiniella, genus, 416.

Peridinium, genus, 398, 399; skeletal
variations, 403, 408; systematic
position, 404, 408; nomenclature
of the plates, 405-407.

Skeletal characters, 408-414, 459;
antapical horn, 409; girdle, 411;
plate patterns, 412, figures show-

the,

413,
438,
461,

311,

ing, 409; size, shape, surface,
ete., 414, 459; plate relationships,
414.

[526]

Plate development, 416-419, 459;
exuviation, 417; origin of acces-
sory plates, 439, 459.

Skeletal variations, regions of, 423,
460; figure showing, 423.

Plate patterns, basis for subdivi-
sion, 426-428; origin of dorsal,
442, 443; paired area of change,
444; completeness of series of
variations, 446-447; variations in
length of critical sutures, 448—
450; significance of variation in
suture length, 450-456; muta-
tions in, 456, 463; influence of
environment on, 457, 465.

Subdivisions, 428, 435; definition,
436; regions of variation in shell
of, 437, 444.

Peridinium achromaticum, 432.

aciculiferum, 432.

adriaticum, 450.

anthonyii, 431.

bipes, 451.

breve, 430.

brevipes, 430.

cerasus, 429.

cinetum, 431.

claudicans, 431, 432, 435, 450, 456,
458.

eonicoides, 431.

conicum, 431, 442, 455.

erassipes, 410, 430, 442.
forma autumnalis, 430.
forma typica, 430.

cummingii, 410.

curvipes, 413, 429, 430.

depressum, 431.

divergens, 430, 435, 442, 448, 449,
450, 451, 452, 454, 463; charts
and figures of plate patterns,
415, 422, 423, 425, 429.

excentricum, 419, 433, 447.

faeroense, 431.

globulus, 430.

granii, 429, 435, 450, 456, 457.

islandicum, 429, 443.

laeve, 432.

latum, 432.

lenticulatum, 430.

leonis, 431.

marchicum var. javanicum, 432.

marsonil, 434.

minutum, 432.
var. tatihouensis, 434, 459.

mite, 413, 430.

monacanthus, 430.

monospinum, 432.

multipunetatum, 432.

obtusum, 431.

oceanicum, 431, 435, 442, 450, 456,
457, 458.

ovatum, 429, 434, 450, 456.

pallidum, 429.

Index

parallelum, 431.
paulseni, 433.
pellucidum, 429.

var. acutum, 429.
pentagonum, 431.
perrieri, 433.
punctulatum, 451.
pusillum, 432.
quadridens, 432, 441.
quarnerense, 430.
rectum, 413, 429.
roseum, 430.
spinosum, 429.
steinii, 410, 430, 445.
subinermis, 431.
tabulatum, 431, 443.
tenuissimum, 410.
thorianum, 403, 432.
tristylum, 429.
trochoideum, 432.
typus, 431.
umbonatum, 432.

var. elpatiewskyi, 433.
westii, 431.
wiesneri, 430.
willei, 431.

Placoides tenuisculptus, 303, 320, 321.

Phalacroma, genus, 405.

Pholadidea penita, 308, 312.

Pholas pacifieus, 303, 320.

Physopsis africana, 488.

Phytoplankton, 200.

‘“Plankton concept,’’ 240, 290; valid-

ity of, 281—287.
Planorbis bahiensis, 488, 489.
boissiyi, 488.
guadelupensis, 488.
olivaceus, 488, 489.
Plasmotomy in Giardia microti, 17.
Polinices lewisi, 314.
Polychaeta, 62.
Polymastix, 382.
Polynoé californica, 177, 213, 218.
complanata, 47.
filamentosa, 177, 183.
fragilis, 177, 213,
showing, 236, 238.

lordi, 177, 213, 224; figures show-
ing, 236, 238.

ocellata, 218.

pulehra, 220, 224, 225, 226.

remigata, 177.

scolopendrina, 221, 226, 227.

Polyzioidae, attributes of, 46; resem-

blance to Aphroditidae, 46; de-
scription, 46; definition of, 174;
division of based on distribution,
174; modes of self defense, 211,
228; changes in, 217; power of
regeneration, 217; muscular adap-
blanee to Aphroditidae, 46; de-
vantage of commensal habits,
219; adaptive coloration, 220,

220; figures

[527]

999.

225; abyssal species, 222; ecto-
parasitic, 224.

Distribution of, 46; tables show-
ing, 176, 178, 184-190; bathy-
metrical, 179, 180, 181, 183; fae-
tors in, 191: temperature, 200,
206, ocean currents, 206, winds,
208, chemical composition of
water, 209, plasticity (variabil-
ity), 213; réle of food in, 211.

Food habits, 47, 210, 211; influence
of, on mode of life, 211-213.

Species of, number, 174; cosmo-
politan, 174; littoral, 182; deep
water, 183; commensal forms,
213, 215; influence on, of environ-
ment, 215, of depth, 215.

Polynoidae from the Coast of Cali-
fornia, Description of Some New
Species of, 45.

Polynoidae of the Pacific Coast of
North America, Factors Control-
ling the Distribution of, 171.

‘*Poreupine’’ expedition, 172.

Port Erin Marine Biological Station,
Isle of Man, 282, 400.

Pottschapel, Saxony, 401.

Pouchet, G., 96.

Pouchetia, genus, 405.

cochlea, 96, 97.

cornuta, 96, 97.

Prorocentrum, genus, 404.

Protoceratium, genus, 416.

Protoperidinium, genus, 411.

Protozoan Cysts in Mammalian
Faeces, A Rapid Method for the
Detection of, 145; description of,
147; value of, 148.

Prowazek, S. von, cited, 1, 256, 358,
378.

Prowazekella. See Prowazekia.

Prowazekia lacertae, 345.

Psephdia ovalis, 303, 320, 321.

Pyrocystis, genus, 405.

Pyrophacus, genus, 416, 420, 427.

Quatrefage, cited, 62.

Raia erinacea, 152, 157.

Ramsay, L. N. G., cited, 207.

Rankin, EK. P., cited, 330.

Reed, A. C., cited, 489.

Retzius, G., cited, 129.

Ritter, W. E., acknowledgment, 241.

Robson, G. A., cited, 487.

Rodenwaldt, E., cited, 5, 21.

Row, R. W. H., cited, 145, 148.

Sacramento-San Joaquin river sys-
tem, 32; tables showing dis-

charges of, 32, 33.
Sagitta bipunctata, 202.
Salinity of San Pablo Bay, 383, 35, 39,
42. See also Teredo diegensis.
Salpa cabotti, 258, 259, 271.

Index

Salpa democratica, distribution, con-
trol of, 240, 286, 290; questions
on, 241; seasonal, 250, 288, ver-
tical, 251, 288, surface, 252, 288;
relations between temperature
and surface distribution, 252-
261, 288, 289, bearing of on
morphology, 256, on locomotion,
261; existence of protruding
chains, 258, 290.

life cycles, 241; relation between
season and temperature, 262, be-
tween position and temperature,
265; viscosity theory, 269, 290;
peculiarities in temperature rela-
tions, 274-281, 289.

locomotion, theory of, 271, 286;
conditions deduced from, 276,
279, 280..-

Salpa democratica, Differentials in
Behavior of the Two Generations
of, Relative to the Temperature
of the Sea, 239.

Salpa fusiformis, 260, 272.

zonaria, 260.

San Diego, California, 68, 448.

San Francisco Bay, distribution of
shipworm in, 27-43; temperature
of, compared with that of Chesa-
peake Bay, 38; physical charac-
ters of, 301; temperature, 302,
salinity, 302-303; diversified bot-
tom, 303; molluscan fauna of,
303-308; economic considerations
concerning, 308-317.

San Joaquin and Sacramento river
systems, 32, 33.

San Pablo Bay, presence of ship-
worms in, 29-42; physical con-
ditions of, 31; salinity of, 33, 35,
39, 42; temperature of, 36.

San Quentin, Point, 316.

Sars, M., cited, 172.

Sausalito, California, 431, 435.

Saxidomus nuttalli, 303, 308, 310,
313, 315, 320, 321.

Schistosoma haematobium, 485; in-
termediate hosts, and _ larval
stages of, 488; cercaria of, 488;
position of miracidium, 509;
hatching of embryo, 516; ex-
cretory system of miracidium,
518. See also S. japonicum; §.
mansoni.

Schistosoma japonicum, method of
transmission, 486; discovery of
intermediate host, 487; egg and
miracidium of, 514-518; rudi-
mentary spine, 514-515.

Miracidium, 515; extrusion of oil
globules, 516; hatching of em-
bryo, 516-517; cephalie glands,
518; exeretory system, 518. See

also Schistosoma haematobium;
S. mansoni.

Schistosoma japonicum, Japanese
Blood Fluke, Cercaria of the,
485.

Schistosoma mansoni, cereariae of,
488, 489; egg and miracidium of,
509-519; egg shell, 510; figure
of egg, 510.

Miracidium, shape, 510; cephalic
glands, 511; nervous system, 512;
excretory system, 513; figures of,
517; flame cells, 513; symmetry,
514; figures of, 511, 512, 513;
extrusion of oil globules, 515—-
516. See also 8. japonicum.

Schistosomiasis, 487, 489.

Schizothaerus nuttalli, 303, 307, 308,
310, 314, 315, 320.

Schott, G., cited, 191, 200.

Schuberg, A., cited, 378.

Schurig, W., quoted, 283.

Schitt, F., cited, 411.

Seripps Institution for Biological Re-
search (Marine Laboratory), 99,
151, 400.

Scyllium, genus, 168.

eanicula, 479.

Scymnus lichia, 152.

Seligmann, C. G., cited, 516.

Setchell, W. A., cited, 175.

Sharp, R. G., cited, 350, 352, 366, 378,
379, 381, 384; quoted, 365.

Shipworm. See Teredo diegensis.

Shipworm in San Francisco Bay,
California. An Unusual Exten-
sion of the Distribution of the,
27.

Sigerfoos, C. P., quoted, 37.

Siliqua nuttalli, 308, 311, 315.

Smith, A. J., cited, 516, 517.

Solen sicarius, 303, 312, 315, 320.

Soule, H. B., U.S.N., member of board
for survey of San Francisco Bay,
300.

South Africa, 488.

Spinax, 168.

Spiraulax, genus, 416, 440, 459.

Spirostomum ambiguum,: 380.

Spisula ecatilliformis, 303, 312, 320.

Squalus sucklii, figure showing sub-
clavian vein and its relations,
480, 482, 483.

Stefanonympha, genus, 383.

Stein, F., cited, 368.

Stentor coeruleus, 371, 378, 379.

niger, 380.

Steuer, A., quoted, 282.

Sthenelais, 127.

Stockard, C. R., 210.

Stovaine, effect of, on nerve cord of
earthworms, 116, 143.

Straub, W., cited, 120, 121, 136, 142.

Index

Strombidium testaceum, 371.
Stylonychia, 341, 356, 378, 380, 381.
Styloplotes, genus, 338.

Subclavian Vein, The, and Its Rela-
tions in HElasmobranch Fishes,
479; studies on, in Heptanchus,
Mustelus, and Squalus, 480-483.

Sumner, F. B., acknowledgment, 241,
300; member of board for sur-
vey of San Francisco Bay, 299.

Sumner, et al., cited, 32, 34, 35;
acknowledgment, 300.

Suzuki, M., 487; cited, 487.

Swezy, Olive, 89; acknowledgment,
2, 173, 340; cited, 9, 366, 382,
383.

Tellina buttoni, 303, 320, 321.

salmonea, 303, 320, 321.

Temperature in abyssal waters, 191,
in the Pacific Ocean, 191, 192—
197, off the Pacific Coast of
North America, 199, 201; factor
in distribution of fauna and
flora, 200, 202, 208, 205. See also
Salpa democratica; San Fran-
cisco Bay; San Pablo Bay.

Teredo diegensis, absence, and pres-
ence, in regions of San Francisco
Bay, 27, 28, in San Pablo Bay,
29; activity of, 28, 40, 42; de-
struction done by, 29, 30, 37, 39;
effect of salinity on, 36, 42; sen-
sitiveness of, 41.

dilatata, 37.
navalis, 37.

Thais lamellosa, 303, 304, 305, 307,
320, 322.

Thelepus, 216.

Thon, K., cited, 380, 384.

Tivila crassatelloides, 308.

Tower, W. L., cited, 210, 225.

Tragosome harrisii, 205.

Transmission, The, of Nervous Im-
pulses in Relation to Locomotion
in the Earthworm, 103.

Treadwell, A., acknowledgment, 172.

Trichoda, genus, 338.

Trichomonas, genus, 382.

Tripsolenia, genus, 403.

Tsuchiya, I., cited, 486, 487.

Turbonilla franciscana, 303, 320, 321.

keepi, 303, 320, 321.

Turris, ef. incisa, 303, 321.

Union Bay, Alaska, 431, 457.

United States Bureau of Fisheries,
Biological Survey of San Fran-
cisco Bay, 299.

Unusual Extension of the Distribu-
tion of the Shipworm in San
Francisco Bay, California, 27.

Uronychia, 370, 371, 372.

Urosalpinx cinereus, 314, 330.

Venezuela, 488.

Vogt, C., 95.

Vorticella, 363.

Walcott, C. D., cited, 171.

Wallengren, H., quoted, 371.

Webber, H. J., cited, 384.

Wenyon, C. M., cited, 1, 21.

Werner, H., cited, 1.

Westwalde, Germany, 401.

Whiting, P. W., cited, 370.

Willemoes-Suhm, R., cited, 212.

Wilson, C. W., cited, 366, 381, 385.

Wooley, P. G., cited, 515.

Wyville Thomson’s Ridge, 202.

Xylotrya gouldi, 37.

setacea, 27.

Yamamoto, J., cited, 486.

Yes Bay, Alaska, 429, 448.

Wocom si Baesolr

Zirfaea gabbi, 303, 304, 305, 307, 320,
321, 322.

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MITOSIS IN GIARDIA MICROTI /£S _

[Fe
BY ig
WILLIAM C. BOECK \ Ma
— ae i
CONTENTS
PAGE
TAREE HDS OS ce a ee gee ea eee ae Pere 1
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PNSSEDY OV NEES) = a Sse ee Bee ee oer aoe NR ore ea ee Eee 16
SDRC OES ep a aE RN Ne re Lee
Correlations of mitosis with cytoplasmic structures and changes .................-- 18
ING UU OTH OG O Nae UT PO TUS case soe a oe ace fw acs ans nce cannons teeae ae eeese oeeente sestoueeas Sete 19
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INTRODUCTON

The investigations of Kofoid and Christiansen (19156) on Giardia
muris showed that multiple and binary fission were carried on in the
free state of the flagellates as well as during encystment, contrary to
the conclusion of Wenyon (1907), Prowazek and Werner (1914) and
others. Previous to this work, no evidence had been discovered for
the occurrence of multiple fission either in the free state or during
encystment. While the investigations on Giardia muris were being
carried on, a new species, Giardia microti, was discovered in the mea-
dow mouse, Microtus californicus californicus (Peale).

In order to affirm further the work of Kofoid and Christiansen
with regard to binary fission occurring in the free state of the flagellate
and also to set forth the process of mitosis, investigations were made
upon this new species, Giardia micrott.

2 University of Califorma Publications in Zoology [ VoL. 18

I wish to acknowledge to Professor Charles A. Kofoid and to Dr.
Olive Swezy my appreciation of the help given me in the various fea-
tures of this research.

MATERIAL AND TECHNIQUE

The meadow mice were collected in fields about a mile from the
University campus. These fields have an abundant growth of long
grass in which the runways of these mice are easily found. In the
afternoon the common ‘‘Catch ’em alive’’ traps were set in these run-
ways, having been previously baited with crushed barley. The mice
were collected the following morning from the traps.

Most of the trapping was done during the rainy season, character-
istic of winter months around Berkeley, and as a result many of the
mice were found dead from exposure in the traps. Often, however, I
could not make an examination of these dead mice the same day I col-
lected them, but waited until the second day; even then the parasites
were often found to be living.

Ordinary smears upon cover-slips were employed. These were
made by cutting out a piece of the intestine about five millimeters long,
moistening it with normal salt solution, and smearing it over the sur-
face of the cover-glass. This was done in order to obtain the flagellates
which adhere to the mucous lining of the epithelium as well as those in
the lumen. Thin smears were prepared from faeces in the rectum and
colon, the material being rolled out upon the cover-slip, in normal salt
solution.

The smears on the cover-slips were fixed in hot Schaudinn’s fluid
and stained in aqueous iron haematoxylin. Mallory’s connective-tissue
stain was also used. It was of importance in bringing out the neuro-
motor apparatus. The intracytoplasmic fibrils stain a bright red
therein, but it was not satisfactory as a nuclear stain. Counter-staining
with eosin made a clear differentiation between the cytoplasm and the
chromatin, and enabled one to trace the course of the flagella, but
upon the whole gave no advantage in the study of mitosis.

The data in this paper are based on the examination of twenty-
three mice, all of which were Microtus californicus californicus (Peale).
From the table given below, it will be noticed that four of the mice con-
tained no parasites, but that these four had been dead several hours at
the time the examination was made. The remaining nineteen mice
were infected, thus making a very high rate of infection.

1917] Boeck: Mitosis in Giardia microti 3

TABLE OF INFECTION

Slides Infection

Series Date Condition of host prepared Colon small intestine Sex

1 10/1/15 Alive Sin hy ies. er Slight 2
13 12730715 Dead several hours 7 ...... Cee eS Slight re
fe 27 30/1o) Se Dead several ‘hours Nie 2285. Heavy fe)
155, AVSX0/Als 1D een EGNGIRILNIO TIS) ee eae Jo
16 12/31/15 Dead 2 days Wipe Pater eet: Heavy J
18 12/31/15 Dead 2 days I Poss ES. Sere Fair J
20 1/4/16 Degdrseveral days «© cr tae eas | | eect Q
gl 1/6716 Alive O20) Sse Heavy, (cysts) 9
22 1/19/16 Alive Teo Eee eee Slight Q
Apeeli2s/16 Dead 1 day EDO ps shack ns Bh aL ee mal he Se Jo
24 1/28/16 Dead 1144 days Of Pend ee eee Fair J
25 1/28/16 Dead 1% days DSS) Ree eee Ge Pe aoe Fair, (cysts) J
26 2/13/16 Alive Gi We settee cha Naas ae Fair Jo
27 = 2/28/16 Dead (time?) See 3, cs Bek oie on, Sag eee 2
28 3/2/16 Alive NG eee eee ener Heavy io)
29 3/4/16 Alive 36 © Cysts Heavy, (cysts) 9?
a0) BYVALIVAKG Alive 22 Not examined Heavy J
Sil BYAVANG) Alive 6 Hexamitus Slight fe)
32 5/1/16 Alive 12 Not examined Heavy fe)
33 5/8/16 Alive 16 Very few cysts Heavy, (cysts) 9
34 5/16/16 Alive Dare Seb hace Sac eee Fair Q
35 5/16/16 Alive ae er eres Heavy io]
36 2/8/17 Alive 8 Not examined Heavy, (cysts) 9

It would seem from the data set forth in the table that these flagel-
lates are very resistant to the degenerative conditions in the tissues
of the host which ensue at the time of death. Of the twenty-three mice
examined, ten were dead ; of these, six still showed the intestinal flagel-
lates present. In two instances the parasites were still living in great
numbers, after the host had been dead two days. Giardia microti
seems to differ from Giardia muris in resistance, the latter remaining
alive for only a few hours, while the former lived for two days.
Beeause of this characteristic hardiness, it seems as if they should
thrive under cultural conditions.

Attempts were made to obtain cultures by placing some of the
intestinal contents with normal salt solution in a eell slide sealed with
vaseline. The parasites lived for only a short time in the preparations.

It will be noticed, from the table, that the duodenum seems to be
the natural habitat of these flagellates. In series 29 and 33 a few
were found just below the caecum, probably preparing for delayed
encystment, or were there through contamination, some forms having
remained on the forceps used in the making of previous smears from

the duodenum. In series 21, 25, and 29 eysts containing only one

4 University of California Publications in Zoology [ Vou. 18

individual each (pl. 1, fig. 12) were found at the posterior end of the
duodenum and close to the caecum; in series 29 and 33 the cysts were
found not only in the small intestine but also in the colon and rectum,
the smears having been made from the faeces. These cysts showed
single individuals with two nuclei (pl.1, fig.12) and the so-called
‘‘eopulation’’ types (Schaudinn, 1903; Rodenwaldt, 1911) with two
individuals in the back-to-back, end-to-end position, and a total of four
nuclei. The latter type is shown in plate 1, figures 13 and 16. In series
33 and 36, cysts with many nuclei (pl. 1, fig. 14) were very abundant
in the small intestine, but only a very few were present in the colon.

With regard to the pathogenicity of these parasites, Kofoid and
Christiansen (1915b) found that Giardia muris caused a chronic enter-
itis; that the walls of the intestine become orange or yellow in color,
flaccid and often inflated with gas. In the case of the meadow mouse,
a chronic enteritis accompanied by the erosion of the mucous lining,
and the disintegration and falling away of epithelial cells and even of
whole villi into the lumen, are the main visible pathogenic effects.

The gas inflation did not oceur in mice examined by me; this con-
dition as found in Peromyscus infected with G. muris is probably due
to the presence of certain gas-producing bacteria and not to the pres-
ence of the flagellates. There is no evidence at hand that Giardia
microti causes a dysentery in the meadow mouse as Giardia intestinalis
causes In man.

That these parasites in turn undergo parasitism, which leads to
deleterious results, is seen in the fact that they are at times covered
with rod-like bacteria, many adhering to the flagella and some occur-
ring as inclusions within the body itself (pl. 1, figs. 3,15). The identity
of these bacteria could not be determined. They occurred in only two
series of preparations. They appear to be surrounded by a clear
space, filled with a liquid and walled off from the rest of the body by
a membrane, or they may be situated in a vacuole.

MorPHOLOGY

The parasites were found to vary from 6 to 16 in length and from
4.5 to 8u in width. The body as seen from the dorsal or ventral sur-
face is pyriform in shape, and, from a partial side view, the dorsal
surface or back is arched (pl. 1, fig. 8). The anterior end of the parasite
is semi-circular. Posteriorly the body tapers gently or abruptly to form
the caudal area. This caudal area is well developed in this species,

1917] Boeck: Mitosis in Giardia microti 5

and presents an appearance not unlike that characteristic of Giardia
intestinalis (see Rodenwaldt, 1911).

The cytoplasm is finely granulated, sometimes appearing quite
uniform in texture, except at the time of and during encystment,
when some degree of coarseness is usually present. The cytoplasm in
the area of the cytostome and in the triangular halo enclosing the
caudal portion of the axostyle and bordered by the intracytoplasmic
portions of the posterolateral flagella is of a still finer constituency and
more finely granulated than that in the other parts of the body.

Compared with G. muris, the species found in eulture mice and
Peromyscus gambelt (See Kofoid and Christiansen, 1915b), G. microte
is found to be from two to three » longer, but somewhat narrower. Its
caudal area is more tapering, resembling that of G. intestinalis as seen
in the microphotographs by Rodenwaldt (1911). There is some indi-
cation that the cytoplasm of G. microti is more finely granulated than
that of G. muris. The parabasal bodies in G. microti are usually
slender, elongated bodies, lying dorsal to and across the axostyle, while
in G. muris these organs are ellipsoidal bodies lying dorsolaterally on
either side of the axostyle. The cytostome in G. microti is seen to
extend more nearly to the periphery of the body than that in G. muris.

The body contains the following morphological structures: the
axostyle, lying medially upon the ventral surfce of the body; two
nuclei, in the eytostomal area and near the axostyle; a centrosome,
embedded in the nuclear membrane at the anterior pole of each
nucleus; the rhizoplasts, connecting the two nuclei with centrosomes
and the blepharoplasts and within the nucleus with the central karyo-
some; and two blepharoplasts (united by an anterior commissure),
situated on the anterior end of the axostyle. A temporary paradesmose
stretches between the divided centrosomes of each nucleus at the time
of mitosis. The anterior chiasma is the point of intersection of the two
anterolateral flagella arising from the blepharoplasts. These flagella
after leaving this point pass to the side opposite that from which they
originated. The anterior and posterior peristomal fibrils border the
periphery of the cytostome; the anterior right and left fibrils are
thicker than the posterior fibrils. The parabasal bodies, composed of
one or two bands of chromatic material, are situated in the posterior
third of the body, and lie upon the dorsal surface of the axostyle.

There are eight flagella: a pair of anterolaterals which border the
anterolateral edges of the animal; a pair of posterolaterals whose
intracytoplasmic portions bound the outer lmits of the clearer cyto-

6 University of California Publications in Zoology [ Vou. 18

plasm in the caudal area; a pair of caudal flagella which arise from
the posterior tip of the axostyle or axostyles; and a pair of free ven-
trals, arising upon the axostyle a short distance back from the ble-
pharoplasts. Basal granules are sometimes visible at the posterior end
of the axostyle, and where the free parts of the anterolateral flagella
emerge from the cytoplasm (pl. 1, fig. 2).

The separate structures enumerated above may now be treated
more fully, as to structures, position, and possible function.

The two oval-shaped nuclei le on either side of the axostyle in the
eytostomal area. In the resting stage (pl. 1, fig.1) each nucleus con-
tains a central ovoid karyosome surrounded by a hyaline space, which
in turn is enclosed by a very definite nuclear membrane. I could find
no signs of peripheral chromatin in the nuclei. The major axes of
the nuclei are slightly directed toward each other anteriorly. The
karyosome is connected to the centrosome on the nuclear membrane at
the anterior pole by a small intranuclear rhizoplast; and the centro-
some in turn is connected with the blepharoplast by a small extra-
nuclear rhizoplast (pl. 1, fig. 1). By means of these rhizoplasts and the
anterior commissure, the nucleus, centrosome, blepharoplast, and flag-
ella of one side are connected with those of the other side, thus form-
ing one integrated system, designated by Kofoid and Christiansen
(1915) as the neuromotor system.

The centrosome of each nucleus, previous to division, varies in size ;
it lies on the nuclear membrane at the anterior pole of the nucleus.
The centrosome of each nucleus is connected by a slender rhizoplast
with the nearest blepharoplast at the head of the axostyle. When the
axostyle splits, the anterior commissure may for a time remain intact,
thus connecting the blepharoplasts of each new axostyle head; and
when the axostyle is not split it appears as a fibril making possible
the establishment (pl. 1, fig. 1) of direct connection between the karyo-
some of one nucleus and the karyosome of the other nucleus. A
paradesmose was best demonstrated with Mallory’s connective tissue
stain ; this fibril connects the two divided centrosomes of each nucleus
and always hes outside of but closely applied to the nuclear mem-
brane (pl. 1, figs. 5, 6, 7). It is a recurrent cell organ in this species.

The two blepharoplasts united by a fibril, the anterior commissure,
le embedded in the material at the head of the axostyle. The blepharo-
plasts appear to initiate mitosis, for they are the first organelles to
divide and are followed by the cleavage of the axostyle. That this is
the case is evidenced by the large number of forms having a partial

1917] Boeck: Mitosis in Giardia microti ft
separation of the axostyle, but as yet there is no mitotic change in the
nucleus, or a cleavage of the centrosome. This, however, as will be
shown later, is the final step of the preceding mitosis. When the ble-
pharoplasts divide, resulting in two smaller blepharoplasts on each
axostyle head, there may be also a splitting of the anterolateral flagella
extending from the blepharoplasts to the anterior chiasma, although
this condition is variable (pl. 1, figs. 9, 17).

Of the eight flagella, the anterolaterals, arising from the blepharo-
plasts, proceed anteriorly, cross each other to form the anterior
chiasma, and then, going to the sides opposite to their place of origin,
lie in the anterior peristome. The intracytoplasmic portions of these
flagella fuse or partially coalesce with the anterior peristomal fibrils,
and are seen to proceed backward, each one later emerging from a
basal granule as a free flagellum. Often the anterolateral flagella
fuse or partially coalesce with the anterior peristomal fibrils, thus
causing these fibrils to be wider than in their usual state (pl. 1, figs.
eT):

The pair of posterolateral flagella seem to arise, as has been said
before, at a point on the axostyle a short distance back from the ble-
pharoplasts. This is contrary to the findings of Benson (1908), who
pictures each intracytoplasmic portion as having a special point of
origin, a basal granule situated alongside of the blepharoplasts. But
the evidence on hand in my material does not confirm his findings. As
these flagella continue posteriorly in their course, they diverge from
the axostyle at an angle of 20° to 30° in a lateral direction. The intra-
cytoplasmic portion is more rigid and thicker than that part of the
flagellum which continues outward as a free whip. There is no basal
granule discernible at the end of the intracytoplasmic portion.

These intracytoplasmic portions of the posterolateral flagella are
close to the surface of the cytoplasm. Observations of living forms
show them to be active, as scull-like propellers in the locomotion of the
parasite. They vibrate in a co-ordinated wavelike manner from side
to side, the vibration starting at the origin of each intracytoplasmic
portion and continuing outward to the end of the flagellum. This
movement is possibly due to the extreme plasticity of the caudal area
of the flagellate’s body. At no time were the intracytoplasmic parts
seen to be separated from the body.

The pair of free ventral flagella take origin at or near the same
point at which the posterolateral flagella arise, but they have no intra-
cytoplasmic portions. In locomotion they are seen to trail behind, and

8 University of California Publications in Zoology [ Vou. 18

like the other flagella vibrate in the characteristic wave-like manner,
the waves always progressing anteroposteriorly.

The axostyle lies on the ventral floor extending from the caudal
area anteriorly, well into the cytostomal area. It lies in the median
plane. Bensen (1908) describes the axostyle as double, composed of
two chromatinic rods; the blepharoplasts situated at their anterior
extremities, each rod continuing posteriorly in a free flagellum. But
according to investigations of Kofoid and Christiansen (1915a and b)
there is more evidence to show that the axostyle is a single rodlike
structure and not a double one, for throughout their study of mitosis
in Giardia muris they found that the axostyle split, forming new ones
for the new individuals. In no ease did they find four rods, as must
be the result of splitting had the axostyle been composed of two rods
as Bensen (1908b) believed. My work on Giardia microti confirms on
this point the findings of Kofoid and Christiansen. The axostyle may
now be said to consist of a single rod, terminating anteriorly with the
two blepharoplasts and posteriorly with the two caudal flagella. It
is but a single undivided rod except as mitosis approaches.

In many eases a basal granule can be seen at the point at which
the posterior or caudal flagella take origin (pl. 1, figs. 2,7). It would
seem quite justifiable to regard the axostyle as the intracytoplasmic por-
tion of the caudal flagella, and therefore probably of flagellar origin
(Kofoid and Swezy, 1915). When the axostyle has completely split,
one flagellum goes to each daughter axostyle (pl. 1, fig. 9) ; the contin-
uity of the intracytoplasmic portions with each caudal flagellum is
easily followed. The axostyle was never observed free from the body of
the flagellate. It is very flexible and may bend upward and downward
or to either side, acting in such a way as to direct the course of the
flagellate in locomotion.

PARABASAL BopIES

The parabasal bodies, composed of one broad, or two narrow bands
of deeply-staining material which in some cases appear to be fused in
one body, are situated dorsal to the axostyle and at the end of the ante-
rior two-thirds of the body (pl. 1, fig. 1). These organs he in a median
plane, extending either to the right or left of the axostyle. In figure
8 it seems to le directly upon the axostyle, or (as in figure 12) it may
be connected with the axostyle by one or more slender fibrils. It plays
no part in mitotic activity. The character of these bodies in Giardia
microti has a striking resemblance to that of similar structures found
in G. intestinalis (see Rodenwaldt, 1911). Rodenwaldt (1911)

1917] Boeck: Mitosis in Giardia microti 9

expresses no theory as to the functions of these bodies, but believed
their presence to be a criterion for determining the age of the flagel-
lates. He says that the bodies are present in old forms and not in
young forms. This conclusion, however, is unwarranted from the
study of G. muris (Kofoid and Christiansen, 1915b)) and from my
study of G. microti, for both small and large forms may be found
without this organ.

In another group of organisms, the trichomonad flagellates, the
parabasal rod is correlated with the well-developed undulating mem-
brane (Kofoid and Swezy, 1915). They found that ‘‘in the absence
of such a localized area the parabasal body or homologue is often more
condensed (not however in trypanosomes) and lies nearer the blepharo-
plast and nucleus, as in Parajoenia.’’ Their final conclusions, how-
ever, are that its function is ‘‘not primarily skeletal, or supporting,
but rather connected with the metabolism of, and possibly also with
the control of, the motor activity.’’

With regard to the function of the parabasal bodies in Giardia
microti an hypothesis may be made based on the evidence revealed in
the study of both the vegetative and encysted forms. From this study
I am led to believe that these parabasal bodies are conveniences on the
part of the flagellate for coping with the intestinal medium in which
it lives; that they are connected with the motor activity and in rela-
tion to the metabolism of the flagellate.

Most vegetative forms have this organ well developed, but oeca-
sionally some will lack it and they may be either large or small forms
(pl. 1, fig. 10) ; some forms show the organ to be small in size (pl. 1,
figs. 4,11). There are three explanations for these differences: First,
an investigation of the parabasals during enecystment reveals the evi-
dence that at the end of encystment the bodies are very faint (pl. 1, fig.
14) or entirely absent (pl. 1, figs. 13, 16), so that when plasmotomy
occurs the daughter individuals would lack this organ (pl. 1, fig. 13) ;
this would explain the absence of this organ in small forms which
recently have been the products of plasmotomy and have not had as
yet sufficient time for the organization of these bodies. Secondly, the
organ may be fading out due to exhaustion from excessive activity on
the part of the host—either motor or mitotic activity in some cases
(pl. 1, figs. 10, 11) ; this may be true in large individuals which may
not show evidence of mitosis. Thirdly, its absence may be due to the
non-absorption of the stain, due to the biochemical state the bodies
were in at the time of the preparation of the material.

10 University of Califorma Publications in Zoology [ Vou. 18

Figs. A-O. Mitosis in Giardia microti Kofoid and Christiansen. Diagram-
matic presentation of the nuclei figured of the individuals illustrated in plate 1.
X 11,000 approximately. .

Prophase figs. A-K; metaphase fig. L; anaphase figs. M—N; telophase, figs.
N-O.

Fig. A. Typical resting stage of nucleus; ellipsoidal karyosome with connect-
ing intranuclear rhizoplast to centrosome.

Fig. B. Mitosis begun; karyosome elongated, extension of linin to posterior
periphery of nucleus in the major axis.

Fig. C. Knotlike spireme formed by contraction of chromatin at various
points, initiating the formation of chromosomes.

Fig. D. Spireme band, showing longitudinal split progressing anteriorly-
posteriorly.

Fig. E. Each spireme strand segmenting into four chromosomes, the action
progressing from the centrosome posteriorly.

Fig. F. Eight or tetraploid number of chromosomes completely formed.

Fig. G. Dispersal of chromosomes. Centrosome has divided, one portion
migrating to posterior pole of nucleus; paradesmose on outside of nuclear
membrane.

Fig. H. Dispersal of chromosomes, linin connecting fibril, paradesmose
present.

Fig. I. Anterior chromosomes serially homologous, or sisters, pair with each
other. Linin connecting fibrils and paradesmose still present.

Fig. J. Pseudosynapsis, in a side-by-side or parasynaptie union of sister
cLromosomes completed, forming four bivalent chromatinie masses. Linin sus-
pending the four masses and paradesmose present.

Fig. K. Four chromatinic masses; paradesmose present; linin assuming
spindle-like form.

Fig. L. Four chromatinie masses on spindle formed from linin. Chromosomes
dividing apparently in a transverse plane, but in what probably marks the end of
a longitudinal division; paradesmose no longer visible.

Fig. M. Showing chromosomes after their division on the spindle, beginning
their migration to their respective poles of the nucleus.

Fig. N. Chromosomes at each pole fused into single mass; constriction of
nuclear membrane.

Fig. O. End of mitosis; two rounded nuclei with central karyosome. Upper
nucleus showing rhizoplast from centrosome to blepharoplast (not figured).

1917] _ Boeck: Mitosis mm Grardia microti ule

The evidence for the connection of the parabasal bodies with motor
activity is mostly morphological in that this organ is found directly
upon the axostyle, a unit of the motor apparatus of the free vegetative
organism. Often these connections can be demonstrated in the cysts
(pl. 1, fig. 12) ; here the connections are very slender fibrils.

By far the best evidence for the metabolic nature and relationship
existing between the parabasal bodies and the organism as a whole is
gained from a study of the cysts. It was found that all forms encysting
had the parabasal bodies, but that they became very much hyper-
trophied (pl. 1, fig. 12). This is explained by the fact that by virtue
of encystment all motor activity is slowed down or ceases, and so the
draft upon the reserve food-supply in the parabasal bodies decreases
or stops and the bodies temporarily enlarge until absorption of food
is cut off by the cyst-wall. They then decrease slowly and even disap-
pear. This view gains more evidence when it is found that in those
eysts in which binary fission of the flagellate had been completed the
parabasal bodies were lacking (pl. 1, figs. 18, 16) and also that in the
multinucleate cysts these bodies were either very faint (pl. 1, fig. 14)
or entirely lacking; in explanation, the bodies had become physically
exhausted because of the metabolic activity which must necessarily
have taken place in the cyst, while the original source of food-supply
had been progressively cut off.

That these bodies are conveniences to cope with the varying
intestinal medium would appear to be established since thus far it
has been found that only the entoparasitic organisms have these
parabasal bodies well developed.

MITOSIS

Mitosis in Giardia microti presents stages characteristic of the pro-
phase, metaphase, anaphase and telophase which are in many respects
homologous to these phases of mitosis in Metazoa.

PROPHASE

The prophase, in which the chromatin is getting ready for its equal
division in the metaphase, is especially marked by the complexity of
nuclear changes, most of which occur previous to the division of the
centrosomes which is the forerunner and initiator of mitosis in the
Metazoa.

At the time when the first mitotic activity occurs, the division of
the blepharoplasts and the beginning of the splitting of the axostyle

12 University of California Publications in Zoology [ Vou. 18

has been completed (pl. 1, fig. 2), but these cytoplasmic changes have
come about long before the division of the centrosome (pl. 1, figs. 5, 6,
7). The division of the blepharoplast in trichomonad flagellates ini-
tiates mitosis, and the question now arises as to the significance of this
division in Giardia microti at the time when mitosis has begun, yet
previous to the division of the centrosomes.

If we consider that Giardia has evolved as a two-celled individual
from a unicellular trichomonad flagellate which had undergone mitosis
but no plasmotomy or division of the cytoplasmic body, then this point
can be easily explained. In the mitosis of trichomonad flagellates, as
has been said before, the blepharoplasts initiate mitosis by dividing and
forming a paradesmose between the two daughter blepharoplasts ; these
blepharoplasts become the poles of the spindle. They appear in func-
tion to be centrosomes as well. However, they still act as the central
point at which the new undulating membrane and the new flagella
will form and so must be considered blepharoplasts (see Kofoid and
Swezy, 1915). It is very significant that in the anaphase these
daughter blepharoplasts temporarily divide to form two smaller gran-
ules, one a ‘‘centrosome’’ and the other a ‘‘basal’’ granule or blepharo-
plast with the paradesmose connecting the basal granules or blepharo-
plasts. This paradesmose in all probability corresponds in part to the
anterior commissure in Giardia microti, the fibril connecting the two
blepharoplasts (pl. 1, fig. 1), which has here become a permanent
structure. It is thus evident that Giardia is a two-celled animal
derived from a trichomonad flagellate which had gone through mitosis
but not plasmotomy. In the trichomonad flagellates these new centro-
somes are only temporary structures and in the telophase the separated
centrosome and blepharoplast reunite to become the permanent ble-
pharoplast. Hence this blepharoplast contains the centrosome. In
Giardia this fusion of the centrosome and blepharoplast has not taken
place, but the separation is permanent, each centrosome occupying a
position on the nuclear membrane at the anterior pole of each nucleus
while the blepharoplast becomes a separate organ at the head of the
axostyle (pl. 1, fig. 1).

Now then, when the axostyle does divide at the time of mitosis in
the prophase in Giardia, this division represents only the delayed
division of this part which would ordinarily have taken place in the
trichomonad stage of the organism after the completion of mitosis.
This structure is now divided to provide the two axostyles of the new
daughter individuals which will later separate after mitosis by plas-

1917] Bocck: Mitosis in Giardia microti 13

motomy. A large central, ellipsoidal karyosome, connected by an
achromatic fibril, linin in nature, to the centrosome (pl. 1, fig. 1; text-
fig. A) is characteristic of each nucleus in the resting stage. The first
mitotic change in the prophase consists of the extension of this nin
fibril posteriorly to a point on the nuclear membrane (pl. 1, fig. 1;
text-fig. B) and the expansion of the chromatin of the karyosome to
form a long, slender, ellipsodial karyosome.

It is to be noted that thus far the nuclear changes have been of
such a nature as to make more pronounced a polarity in the nucleus.
This is marked by the extension of the linin fibril posteriorly and the
expansion of the chromatin anteriorly and posteriorly on it. This
polarity of the nucleus can be followed in later stages. It is related
to the polarity exhibited by the cytoplasmic structures, especially to
the main axial structure, the axostyle, which defines the poles and
main axis of the body of the organism itself, although the axes of the
two nuclei are not quite parallel to this major axis of the body. The
longitudinal and what appears to be an equivalent splitting of this
spireme to form two single, somewhat ragged spireme strands in each
nucleus soon follows (pl. 1, fig. 3; text-fig. D). The splitting begins
in the area adjacent to the centrosome and proceeds posteriorly and
completely through the spireme band. These two spireme strands in
each nucleus soon show the beginnings of the differentiation of the
chromosomes by localized knotting up of the substance, which exhibits
itself first at the end nearest the centrosome (pl. 1, fig. 3, right
nucleus; text-fig. D). Thus from this progressive action in the split-
ting of the spireme and in the formation of the chromosomes, the cen-
trosome, the center of mitotic activity, exerts its influence on the
mitotic process.

After the formation of the split spireme, localized contraction and
tranverse segmentation of the chromatin on these strands ensues to
form four chromosomes from each strand, or eight chromosomes for
the tetraploid number of each nucleus (pl. 1, fig. 6; text-fig. F). An
intermediate stage shows the chromosomes first completely formed
nearest the centrosome, again giving evidence of the fact that mitotic
activity proceeds from the still undivided centrosome, as though
under its influence, towards the opposite pole. The chromosomes are
seen to be connected end to end by linin fibrils, forming two chains of
four chromosomes each. These chains are in most cases parallel to
the major axis of the nucleus, thus maintaining the same polarity
(pl. 1, figs. 4, 5, 6).

14 University of California Publications in Zoology [ Vou. 18

It is significant to note here that the chromosomes arrange them-
selves into two groups of four each and that the line of separation. is
at the equator of the nucleus (pl. 1, fig. 5; text-fig. F). This suggests
the possibility of a biparental origin of the chromosomes, and indicates
the probability of the occurrence of sexual reproduction in Giardia,
but there is as yet no evidence for this assumption. The lnin con-
necting fibrils between chromosomes are present at this stage of
mitosis.

The chromosomes appear to be oblong in shape, about 0.3 long
and about 0.24 in width. The chromosomes derived from a single
spireme strand in a nucleus show immediately after their formation a
tendency to pair off with the adjacent chromosomes derived from the
other spireme strand of the same nucleus (pl. 1, fig. 5; text-fig. F).
The chromosomes appear to be very much alike in shape and size.
More evidence for polarity within the nucleus is displayed by the
chromosomes in that their long axes are parallel to the long axis of
the nucleus itself, as the chromosomes are differentiated in two linear
axial lines in the nucleus (pl. 1, fig. 5; text-figs. F, G).

Thus far it must be noted that all these mitotic changes, including
the formation of the eight or tetraploid number of completely divided
chromosomes, have taken place before the division of the centrosome
or any evidence of activity therein, and that throughout the process
thus far all nuclear changes have consistently displayed a polarity
related to that of the polarity of the nucleus itself and of the organism
as a whole in the direction comparable to that of the axial gradient
of Child.

On the division of the centrosome of each nucleus at this time, one
daughter centrosome remains fixed while the other one migrates to a
point on the periphery of the nucleus at the opposite pole 180° from
its original situation, and here marks the posterior pole of the spindle
to be formed later (pl. 1, fig. 5; text-fig. G). A paradesmose lying
outside the nucleus but closely applied to the nuclear membrane is
formed as a connecting fibril between the two daughter centrosomes.

The chromosomes at this stage, as has been previously stated, may
often be seen to be still connected in an end-to-end manner by linin
fibrils, but there is a tendency now for them to disperse throughout
the nucleus; this progressive stage and the one preceding are often
found in the two nuclei of the same individual (pl. 1, fig. 5). Because
of this dispersal there is given the opportunity for a rearrangement
of the chromosomes different from that of their first order, but there

1917] Boeck: Mitosis in Giardia microti 15

seems, however, a tendency for them to return later to approximately
the same position as that which they occupied in the split spireme
when first formed. The uppermost chromosome of each spireme band
comes to lie side by side with its mate of the opposite strand (pl. 1, fig.
6; text-fig. 1). Lower chromosomes continue this pseudosynaptie side-
by-side pairing. After this pairing a rather intimate lateral fusion
of these pairs takes place. This is a fusion on a plane identical, or
at least parallel, with that of their original separation. What is prob-
ably the beginning of this pairing and fusion of chromosomes number
1 is seen in the uppermost end of the left nucleus in figure 6 (plate 1),
while the same chromosomes in the right nucleus also appear to be
approaching each other. The end result of this fusion is four chroma-
tinie masses, each composed of two chromosomes which have previously
split and then fused (pl. 1, fig. 7; text-figs. J, K). Here again there
is evidence that each one of these masses is so situated that its long
axis 1s still nearly the same as that of the nucleus and approximately
that of the whole cytoplasmic body. This is also true for plane of
fusion, which is parallel to the plane which involves the long axis
(pl. 1, fig. 7; text-fig. J).

The spindle is now formed from the linin of the nucleus. Just
previous to spindle formation the linin is a central mass upon which
the four chromatinic masses are situated (pl. 1, fig. 7; text-figs. J. K).
Often it seems to be shaping itself into a spindle-like structure
approaching prematurely the structure of the later spindle (pl. 1,
fig. 7, left nucleus). The spindle may partially or entirely fill the
nucleus (pl. 1, figs. 8,9). The condition in which the spindle partially
fills the nucleus is probably due to plasmolysis at the time of the fixa-
tion of the material.

With spindle formation, these four chromatinic masses come down
into the equatorial plate (pl. 1, fig. 8; text-fig. L). On the spindle
they appear to be elongated and to be getting ready for tranverse divi-
sion in the metaphase. Because of the position of these chromatinic
masses on the spindle it is probable that when the chromosomes pre-
viously fused side by side (pl. 1, fig. 7) they next began to pull apart
at one end and this proceeded more and more until finally these
chromosomal members of each chromatinic mass came to an end-to-end
position, though still fused in that region and are shown in this stage
(pl. 1, fig. 8) in the equatorial plate on the spindle ready for final
separation at the close of the metaphase.

This pairing of chromosomes and their subsequent fusion might

16 University of Californa Publications in Zoology [ Vou. 18

be called a pseudosynaptic phenomenon. There is no evidence that a
true synapsis occurs in any premitotic phases observed by me, more-
over, thus far no sexual reproduction has been discovered in Giardia.
Since, however, each chromosome seems to show a tendency in this
stage in ordinary vegetative mitosis to fuse with the corresponding
chromosome of its sister spireme strand, this relationship is strictly
one devoid of all true synaptic relations, and so can be looked upon as
wholly pseudosynapsis.
METAPHASE.

The four chromatinic masses now at the equator of the spindle
appear to divide by transverse constriction through the center of each
mass (pl. 1, fig. 8; text-fig. J); the division is equal. It results in
the re-formation of eight chromosomes, two each from the four masses
formed from four chromosomes which had previously split and then
come together and fused. But, as has been said before, this apparent
transverse division of these four chromatinie masses is not true trans-
verse fission, but is rather an end-to-end separation, the completion
of a division along a longitudinal plane which is identical with the
plane of fusion of the two chromosomes.

Again the chromosomes seem to be of uniform size (pl. 2, fig. 9)
and there is evidence here of their recent separation from other
chromosomes (pl. 2, fig. 9, left nucleus). For convenience we may
consider the chromosomes in this nucleus in the right and left hemi-
spheres. The two chromosomes above the equator in the right hemi-
sphere were probably separated from the two chromosomes below the
equator in the same hemisphere. Likewise the two chromosomes above
the equator in the left hemisphere were separated from the other two
chromosomes below the equator of the same hemisphere. It is possible
that these four chromosomes in the left hemisphere which are farther
separated from each other than those in the right hemisphere are the
upper chromosome pairs, and that, as in previous stages they were
formed first because of their proximity to the centrosome, so here,
not for the same reason, but because of their holding on to their prop-
erty of priority of change, they have been the first to become separated
and already have migrated farther than those in the right hemisphere.

ANAPHASE

This phase is noted by the migration of the chromosomes to the
poles of the spindle. The beginning of this phase shows the individual
chromosomes near each other subsequent to the division in the meta-
phase (pl. 1, fig. 9; text-fig. M). Often inequality of nuclear changes

1917] Boeck: Mitosis in Giardia microti LZ

on the two sides of the organism occurs. This is exemplified in figure
9, where the left nucleus is in the anaphase, and the right nucleus dis-
plays the four chromatic masses previous to their arrangement at
the equator of the spindle. Another case, earlier in mitosis, is seen in
figure 5.

The chromosomes in the course of their migration fuse into two
chromatinic masses, one mass going to either pole (pl. 1, fig. 10; text-
fig. N).

TELOPHASE

With the formation of each chromatinie mass produced by the
fusion of four chromosomes at each pole, the nuclear membrane begins
to constrict (pl. 1, fig. 10; text-fig. N). The completion of this process
results in two daughter nuclei (pl. 1, fig. 11; text-fig. O) on each side
of the body. The upper two may still be connected by the small extra
nuclear rhizoplast to the blepharoplast nearest each centrosome; the
intranuclear rhizoplast as yet has not been differentiated (pl. 1, fig.
11) but undoubtedly occurs later as an outgrowth from the linin sup-
porting the karyosomes. The reconstruction of the nuclei except for
this intranuclear rhizoplast is thus completed. The linin of the spindle
has again collected to form the network upon which the chromatin
of the karyosome is suspended. Mitosis is now completed and is to be
followed by plasmotomy.

PLASMOTOMY

Plasmotomy, or the division of the parent cytoplasmic body to form
two daughter individuals, is not well understood. Only two cases
were found in my material, one of which is figured (pl. 1, fig. 15).
But from the study of these two stages and from like study upon
Giardia muris by Kofoid and Christiansen (1915b), the plane of
cleavage appears to be longitudinal, and the last point of cohesion
of the two daughter flagellates to be at their caudal areas. This
would result in the equipment of each daughter flagellate with two
of the daughter nuclei, an axostyle, and a complete peristome.
Whether or not this is the method in the ease pictured in this paper
(pl. 1, fig. 15) cannot be definitely determined, for the anterior peris-
tomal fibrils of the lower daughter flagellate are fainter than those of
the upper but this may be due to the non-absorption of the stain. The
division of the cytoplasmic body is not equal in this case, but this
again is similar to cases found in Giardia muris (Kofoid and Chris-
tiansen, 1915d).

18 University of California Publications in Zoology [ Vou. 18

CORRELATION OF MITOSIS WITH CYTOPLASMIC STRUCTURES AND

CHANGES

That there are effects or changes possible in the cytoplasm which
can be correlated with mitotie activity taking place in the nucleus is
probably not doubted by any cytologist, but owing to the fact that this
problem of finding these correlations in the cells of Metazoa and Pro-
tozoa alike is wrapped up with biochemical and physiological com-
plexities, investigation in this field is attended with many difficulties.
In the Protozoa, although the biochemical and physiological conditions
are as complex as are those of metazoan cells, yet certain definite corre-
lations between mitosis and cytoplasmic structures and changes can
be the more readily detected because of the unusual development of
cytoplasmic organs in these lower organisms.

The first change to be noted is the division of the blepharoplasts
and axostyle at the beginning of the prophase. This division of the
axostyle, as has been said in the discussion of mitosis, represents the
delayed division of this cytoplasmic organ following and belonging to
a previous mitosis. It is a cytoplasmic phenomenon which precedes
or initiates the next nuclear divisions, although it is completely
detached, except for the rhizoplast, from the centrosome.

The phenomenon of polarity exhibited by the chromatin in its
arrangement during the prophase, as well as the direction of the major
axis of the spindle, is very significant in that for the most part it is
definitely related to the polarity of the body as a whole. Not only
was the single knotlike spireme nearly parallel to the major axis of the
nucleus, but also the two split spireme strands, and the major axes
of the chromosomes when they were completely formed.

Very significant in importance is the seeming influence of the
centrosome. It was previously noted under mitosis that in the pro-
phase the distribution of the chromatin of the karyosome proceeded
along the axis or rhizoplast originating in the centrosome and extended
distally in this axis to the opposite pole to form the single axially
located spireme. Again, when this spireme split, the split proceeded
from a point in the chromatin nearest the centrosome posteriorly ;
likewise when the chromosomes were formed the first ones to be com-
pleted by segmentation of the spireme strands were located near the
centrosomes. The centrosome, even before its division, by the behavior
of the chromatin gave evidence of its potential influence over the
mitotic process. The entire number of eight chromosomes was, how-

1917] Boeck: Mitosis in Giardia microti 19

ever, completely formed previous to the division of the centrosomes,
but their final separation, after the previous parallel fusion in pairs,
came as it does in mitosis of Metazoa, after the centrosomes had
divided.

The behavior of the blepharoplasts, and axostyle, the distribution
of the chromatin in the nucleus, and the influence of the cytoplasmic
structures, the centrosomes afford clear morphological evidence for
the correlation of mitotic activity with changes in the cytoplasm.

NEuRoMoTOR APPARATUS

The evidence of the presence of a unified system of structures
which may be closely associated with the motor and sensory activi-
ties of Giardia was brought forward by Kofoid and Christiansen
(1915a,b). They called this system the neuromotor apparatus.

In Giardia microti this same system appears, and here may be’
briefly described. Figure 1, plate 1, is indicative of what is present
in all forms. The neuromotor apparatus may be conceived as consti-
tuting here a union of the fibrillar system with the nuclear system. As
has been said before, the two nuclei are connected together by rhizo-
plasts, which on their route join the centrosomes and the blepharo-
plasts.

The blepharoplasts together constitute the center of the fibrillar
system. Connected to the axostyle are the anterior and posterior
peristomal fibrils, the posterolateral flagella by means of intracyto-
plasmic portions, then the free ventral flagella, the pair of caudal
flagella, and the parabasal bodies. The anterolateral flagella arise from
the blepharoplasts. Thus all the fibrillar and motor parts are con-
nected directly to the blepharoplasts, or indirectly by means of the
axostyle, and, since the blepharoplasts are connected directly with
the centrosomes and nuclei, there exists a definite integration into a
single system of both the nuclear and fibrillar structures. The great-
est metabolic activity takes place in the cytostomal area, and here we
find the neuromotor apparatus conspicuously in evidence by virtue of
the continuous fibril (peristomal fibril) bordering this area. This
condition is analogous to the condition found in metazoan animals,
such as trematodes and cestodes, wherein we find the presence of
nerye-rings associated with sucker-like organs of attachment. Because
of the close association of this unified system with the areas of motor
and metabolic activities, these regions presupposing the existence
of structures for the accommodation of motor and possible sensory

20 University of Californa Publications in Zoology [ Vou. 18

impulses, this unified system has been compared to the nervous sys-
tem of metazoans, and is probably more closely allied to the mechanism
of the reflex are, and therefore called the neuromotor apparatus. The
fibrils stain red in Mallory’s connective-tissue stain, which is char-
acteristic of nervous fibrils in the Metazoa.

The neuromotor apparatus forms one entire integrated system for
regulating and controlling the motor activities of the organism. The
fibrillar division of this apparatus, composed of the eight flagella and
their intracytoplasmic portions, are the organelles for locomotion. In
the study of living forms all flagella are seen to vibrate synchronously
and with the same rapidity when the flagellate lies upon its dorsum.
The members of each pair of flagella vibrate together and at the same
rate. The axostyle also undulates, as do the intracytoplasmic portions
of the posterolateral flagella, the waves of vibration commencing at
their proximal ends and continuing outward to the ends of the free
flagella. When an increased rate of locomotion takes place it results
from increased activity of all the flagella. It appears that the course
of the animal in locomotion is directed by the tail, which acts as a
rudder bending up and down, or from side to side. When the flagel-
late comes in contact with an obstacle the axostyle, because of its
rigidity, serves as a lever to push away from the impediment.

The turning or rotating movement of the flagellate in locomotion
is due to the combination of three factors—the concavity present
between the intracytoplasmic portions of the posterolateral flagella;
the action of the axostyle in bending up and down and from side to
side ; and the position and increased activity of the flagella; the direc-
tion of their stroke, whether straight back or oblique, is dependent
on the position of the flagella, an oblique direction of the stroke tend-
ing to rotate the organism (pl. 1, fig. 8).

Cysts

The eysts of G. microti are ellipsoidal in shape, varying in size
from 6.7x8.5u to 7x13.34. In all eases these cysts are easily identified
by the thick, firm cyst-wall and the scattered remains, now and then
still intact, of the parabasal bodies and of the neuromotor apparatus.
The cysts occur both in the small and large intestine, but predomi-
nantly in the latter. Many of the cysts show a condensation of the
protoplasm and its withdrawal from the eyst-wall (pl. 1, figs. 18, 16).
This is probably due to plasmolysis at the time of fixation in the prepa-
ration of the material.

1917] Boeck: Mitosis in Giardia microti PAL

These cysts of Giardia were identified very early by various
workers, among them Grassi and Schweiakoff (1888), Wenyon (1907),
Bensen 1908), and Rodenwaldt (1911). Because of the various
morphological aspects which these cysts present during different stages
in their development, certain stages have received names designating
them as definite types of cysts.

Prior to the appearance of the paper ‘‘On Binary and Multiple
Fission in Giardia muris’’ by Kofoid and Christiansen (1915b), only
three types of cysts were identified. The first type, ‘‘single indi-
vidual’’ cysts (pl. 1, fig. 12), was described by the early investigators,
Wenyon (1907), Bensen (1908) and others. The second type, or
‘‘binary fission’’ cyst, contained four nuclei, and direct evidence for
the cleavage of the body to form two individuals (pl. 1, fig. 16). The
cysts containing four nuclei were seen by Wenyon (1907) and Roden-
waldt (1911). The third type, the ‘‘copulation’’ eyst, included those
in which two individuals were found (pl. 1, fig. 13). These differed
from the second type in that the organisms, although separate,
appeared to be in a state of partial fusion, suggesting copulation.
Schaudinn (1903), in a footnote, refers to Giardia cysts in which he
found two individuals adhering to each other by their cytostomal
areas, and interpreted this act as one of copulation. It is from this
interpretation that this type has received the name of ‘‘copulation’’
cyst.

It was the prevalent view previous to the paper by Kofoid and
Christiansen (1915b) that reproduction in Giardia took place only
within the cysts, for no binary or multiple fission of these organisms
had been seen in the free state. This paper, representing the results
of work on Giardia muris, revealed evidence of the occurrence of
binary and multiple fission in both the free and encysted states of
Giardia muris. The work of Kofoid and Christiansen also disclosed
another type of cyst which may be ealled the ‘‘multinucleate’’ cyst,
for in it were found as many as sixteen nuclei. This type was also
found in Giardia microti by the same workers (see Kofoid and Chris-
tiansen 1915a). The question was raised by these authors whether
certain of these multinucleate cysts with unequal nuclei might repre-
sent possible maturation stages or whether the multinucleate condi-
tion present was due to ‘‘multiple fission of two individuals in the
stage of advanced plasmotomy.’’

In the light of the evidence upon eysts gathered in my work on
G. microti, the four enumerated types of eysts would seem to resolve

22 University of California Publications in Zoology [ Vou. 18

themselves into only three types. The first, that of the ‘‘single indi-
vidual’’ cysts (pl. 1, fig. 12), the second, ‘‘binary’’ cysts (pl. 1, figs.
13, 16), and the last the ‘‘multinucleate’’ cysts (pl. 1, fig. 14). The
binary cyst is In all probability the same as the so-called ‘‘copulation’’
cyst; in the latter case complete separation of the cytoplasmic bodies
has oceurred, while in the former the cleavage of the parent body is
still in process.

In the results of my study of the ‘‘multinucleate’’ cysts there are
no grounds for attributing maturation phenomena to the parasite
after encystment. No evidence was found which could be interpreted
as progressive fusion of two individuals in a eyst; and when nuclei
appeared larger, it was because they had another division to undergo;
furthermore, no evidence for a reduction of the four ancestral chromo-
somes to two chromosomes was ever found; the chromatin content
appeared equal for all the sixteen nuclei.

The sixteen nuclei came, therefore, as a result of multiple fission,
three progressive divisions having taken place.

CONCLUSIONS

1. Mitosis in Giardia microti presents phases characteristic of
mitosis in Metazoa, viz., prophase, metaphase, anaphase and telophase.
The normal number of chromosomes is four.

2. The nuclear membrane of each nucleus persists during the
entire process of mitosis.

3. The prophase presents many peculiar and complex nuclear
changes:

(a) The karyosome elongates to form a single spireme band sup-
ported by a linin-hke substance in the main axis of the nucleus.

(b) The single spireme band in each nucleus splits longitudinally
from the centrosome distally to form two spireme strands.

(c) Each spireme strand segments to form four chromosomes.
The segmentation proceeds from the region of the centrosome poste-
riorly, due to the probable influence of the centrosome.

(d) Through all these stages the chromatin in its distribution on
the spireme exhibits a polarity related to that of the body of the flagel-
late; the long axis of the chromosomes also shows this polarity.

(e) The eight chromosomes formed appear at first in two groups
of four chromosomes each, one group above the equator of the nucleus
and the other group below, suggesting biparental origin.

1917] Boeck: Mitosis in Giardia microti 23

(f) The chromosomes are about 0.34 in length and narrower in
width, uniform in size and show little or no differentiation.

4. The centrosomes divide after the formation of the eight chromo-
somes; a paradesmose is formed between the daughter centrosomes,
one of which migrates 180° and the other stays fixed at the position of
the parent centrosome.

5. Dispersal of the chromosomes in the nucleus takes place, fol-
lowed by their pairing in an order which seems to be that of their
former splitting and constriction in the spireme strands. The upper-
most chromosome of one spireme strand fuses with its mate of the
sister spireme strand, ete. This is a pseudosynaptic phenomenon.

6. The four chromatic masses thus formed come down on to the
spindle formed from the linin.

7. Later the chromosomes of each mass all appear in an end-to-
end position before final separation in the metaphase.

8. In the metaphase, what is apparently a transverse division of
the chromatic mass to form the equivalent and uniform chromosomes,
is in reality the end of a longitudinal splitting which commenced pre-
vious to or at the time of the metaphase. The original plane of fusion
becomes the plane of division in the metaphase.

9. In the anaphase the four chromosomes migrating to either pole
in each nucleus fuse to form a chromatic mass near each pole of each
nucleus.

10. Completion of the constriction of the nuclear membrane results
in four daughter nuclei in which reconstruction has taken place.

11. The division of the axostyle prior to mitosis represents the eyto-
plasmic change of a previous mitosis.

12. All changes in mitosis are closely correlated with structural
changes in the cytoplasm.

13. The cysts may be grouped under three types: (a) ‘‘single indi-
vidual’’ cysts; (b) ‘‘binary fission’’ eysts; (c) ‘‘multinucleate’’ cysts ;
no stages were found in the material studied which were indicative
of copulation on the part of the individuals and the fusion of their
nuclei, or of maturative phenomena.

14. The organelles of the fibrillar system, together with the two
nuclei and their related structures, present a single unified and inte-
grated complex, which constitutes the neuromotor apparatus.

Transmitted March 9, 1917.

24 University of Californa Publications in Zoology [ Vou. 18

LITERATURE CITED
BENSEN, W.
1908. Bau und Arten der Gattung Lamblia. Zeitschr. Hyg. u. Infekt., 61,
109-114, 6 figs. in text.
GRASSI, B. and SCHEUIAKOFF, W.
1888. Beitrige zur Kenntnis des Megastoma entericum. Zeitschr. wiss. Zool.,
46, 143-154, pl. 1.
Koro, C. A., and CHRISTIANSEN, E. B.
1915a. On Giardia microti sp. noy. from the meadow mouse. Univ. Calif.
Publ. Zool., 16, 23-29, 1 fig. in text.
1915b. On binary and multiple fission in Giardia muris (Grassi). Ibid., 16,
30-54, pls. 5-8, 1 fig. in text.
Kororp, C. A. and Swezy, O.
1915. Mitosis and multiple fission in trichomonad flagellates. Proc. Am.
Acad. Arts and Sci., 51, 290-378, pls. 1-8, 1 fig. in text.
PROWAZEK, S. v., and WERNER, H.
1914. Zur Kenntniss der sog. Flagellaten. Arch Schiff— u. Tropenhyg., 18,
Beiheft 5, 155-170, pl. 10, 1 fig. in text.
RODENWALDT, E.
1911. Flagellaten (Trichomonas, Lamblia) in Prowazek Handbuch der patho-
genen Protozoen, 1, 78-97, pl. 3, 9 figs. in text.
SCHAUDINN, F.
1903. Untersuchungen tber die Fortflanzung einiger Rhizopoden. Arb.
kais. Gesundh., 19, 547-576.
WENYON, C. M.
1907. Observations on the Protozoa in the intestine of mice. Arch. Prot.,
Suppl. 1, 169-201, pls. 10-12, 1 fig. in text.

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i) Patan Cae oie OEE HR Se, ne
i Ge g ioe bar bien}: nt a a
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; [ on he

on

EXPLANATION OF PLATES

All figures of Giardia microti, Kofoid and Christiansen, drawn with camera
lucida from smear preparations as described in paper. Magnification 2,750.
Full length of flagella not shown in many figures.

PLATE 1

Fig. 1. Ventral view, trophozoite in resting stage; note basal granules of
anterolateral flagella and the axostyle as a single rod.

Fig. 2. Ventral view showing elongated karyosome and linin extension;
basal granules for caudal flagella.

Fig. 35. Ventral view, prophase—knot-like spireme, and split in right
nucleus—stage previous to segmentation of spireme bands to form tetraploid
number of chromosomes. Parabasal; bacterial inclusions.

Fig. 4. Ventral view, prophase—spireme of two strands; contraction of
chromatin to form chromosomes, axostyle partially split, parabasal body.

Fig. 5. Ventral view, prophase—precocious splitting to form eight chromo-
somes or tetraploid number. In left nucleus separation of chromosomes to
show possible ancestral origin. Linin fibrils between chromosomes; paradesmose.

Fig. 6. Ventral view, prophase—precocious splitting of double spireme
band of each nucleus, forming tetraploid number of chromosomes, paradesmose

Fig. 7. Ventral view, prophase—four chromatinic masses resulting from
fusion of the tetraploid number by pairs and their consequent contraction into
single mass; centrosome divided; axostyle partially divided; basal granules.

Fig. 8. Lateroventral view, late prophase—four contracted chromatinic
masses at the equator.

Fig. 9. Ventral view, metaphase—equatorial plate in right nucleus; eight
chromosomes. Axostyle divided, blepharoplasts divided and formation of new
anterolateral flagella as far forward as chiasma. Right nucleus in prophase.

Fig. 10. Ventral view, late anaphase or early telophase—chromosomes
fused at poles. Nuclear membrane constricting. Axostyle almost completely
split.

Fig. 11. Ventral view, telophase completed—four nuclei; small parabasal.

Fig. 12. Dorsal or ventral view, ‘‘single individual’’ eyst—large para-
basals with connectives to axostyle.

Fig. 13. Lateral view, so-called ‘‘copulation’’ cyst, but in reality the end-
result of binary fission. New organelles differentiating.

Fig. 14. Dorsal or ventral view, ‘‘multinucleate’’ cyst—sixteen nuclei;
remains of two neuromotor apparatuses; parabasals.

Fig. 15. Ventral view, binary fission—axostyles partially split; anterior
peristomal fibres of lower individual faint because of body being turned back-
ward. Bacterial inclusions.

Fig. 16. Dorsal or ventral view, ‘‘binary fission’’ cyst—four nuclei; two
sets of neuromotor apparatuses.

Fig. 17. Ventral view, metaphase—new anterolateral flagella as far as
chiasma; splitting of posterolateral flagella; equatorial plate formation.

[26]

(BOECK) PLATE 1

18

UNIV. CALIF. PUBL. ZOOL. VOL.

UNIVERSITY OF. CALIFORNIA PUBLICATIONS (Continued
17. Notes on the Local Distribution and Habits of the Amphibians. and

Bg he 4 3 he EB Sem RAS SRR AGE He ean Oe Se Me aaa toa Sand we oe a
Index, pp. 545-558.

1-20, plates.1-2. April, 1914... mesa ee tare te in Mi
i fo Study of the Occurrence and ‘Manner of “Distribution “ot ‘the Crano-

ue April, AGIs: oe os Cg Sg POSE Sk
ca. $e A New Self-Regulating Paraffin Bath, by o. “W. Woodworth. “Pp. 39-
42.2 text-figures. . April, 1914 2 See es ; ast

~ _&. Diplodinium ecaudatum, with an Account of Tits N ‘euromotor A Apparatus,
; by Robert G. Sharp. Pp. 43-122, plates 8-7, 4 text figures. May,

San Diego Region, by Calvin O. Esterly. Po. 128-145. May, 1914...
6. The Anatomy of Heterodontus francisci. I. The Exoskeleton, by J.

esis 2B eS es a 7 eta oasis eR ORs = le NC See OOM SRR or ah Neate Ni hee eo PNR
Frog, by 8. J. Holmes, Pp. 167-174, plate 10.. August, 1914

: Zoological Museum of the. University of California, by Aaron. L.
Se Treadwail. Pp. 175-234, plates 11-12... «
pos ot . 9 New Syllidac from San Francisco Bay -(collected by the U: 8.8.
Osa Sea ~~ oo 0s **AYbatross’’), by Aaron L. Treadwell. Pp. 235-238, 7 text figures.
Nos. 8 and 9:in one cover. October, 1914.20.20 ee
10. Note on the Medusan Genus Stomoldphus, from San Diego, by Heury
B.. Bigelow. Pp.’ 239-241. ‘September, 1914 5.2.2

ae GG eeueue nomic ‘Significance, by Asa C. Chandler. Pp, 243-446, plates 13-17,
e 3 ips WP COKE ALO ULES. S PLOT AN od ON Gop ns ae ed Sonya agape dened ait Ih phan wablaneiaeade
12. Anatomical Adaptations in the Thoracie Limb of the California Pocket

~-- 494, plates 38-39, 20 text-fignres,: Biaren, 1916 <n cas
18. The Inheritance of Extra Bristles in Drosophila Melanogaster Meig., by
Edna M. Reeves. . Pp, 495-515, 1 figure in text. December, 1916 ........

upon the Operations of the United States Fisheries Steamer ‘‘ A¥ba-

sross’’ during the Years. 1912 and 1913, by F. B. Sumner, G. D.

Louderback, W. L. Schmitt, E. ©. Johnston. Pp. 1-198, plates 1-13,

20 textfiguroes. sSnly,(1Ote a hn sea
Vol. 15. Introduction. Dependence of Marine Biology upon Hydrography and
Necessity of Quantitative Biologicel Research. Pp. i-xxiil, June,

PONG eae Be SS See eg ee et ts i Se cee Suet cuca e eas oe

1. Hydrographic, Plankton, and Dredging Becords of the Seripps Institu-

tion for Biological Research of the University of California, 1901 to

1912, compiled and arranged under the supervision of W. EH, Ritter

by Ellis L. Michael and George F. McHwen, Pp. 1- 206, 4 text figures

Sane mane only, Tote too ek a ee OA ee oes.

2. Continuation of Hydrographic, Plankton, and Dredging Records of the

; Scripps Institution for Biological Research of the University of Cali-

fornia (1913-1915), compiled and arranged under the supervision of

~ 'W. B. Ritter, by Ellis L: Michael, Zoologist and Administrative As-

sistant, George F. McEwen, Hydrographer. Pp. 207-254, 7 figures in

text. November, LCR & 6 tipple ace ath re airy DEAS esas BN th apna eG Cer oO care Soe

8. Summary and Interpretation of the Hydrographic Observations made by

the Scripps Institution for Biological Research of the University of

sag California, 1908 to 1915, by George F. McEwen, Hydrographer.
ee Ppy 255-556, “plates-1-38.5 December 1916-2 = ss

Wis ‘VoL 16. 1. An Outline of the Morphology and Life History of Crithidia lepto-
ern coridis, sp. nov., by Trene McCulloch, : ‘Pp. 1-22, plates 1-4; 1 text

PUES. “SEptenn per. 71 O LOs5 as ee eee Gh ee A

% easy ‘Atwood Kofoid: and Elizabeth Bohn. Christ spser- Pp. 23-29, 1 figure

pee? aan Sexte

Sa aia 8. On Binary and Multiple Fission in Giardia nips (Grassi), by Charles
* Atwood Kofoid and Elizabeth Bohn Christiansen. Ee: 30-54, anise

5-8, 1 figure in text.

Basso See Nos. 2 and $ in one cover. ‘November. A pF ieee ord ane na eaee eater

Ben ee yy, eS 4. The Oultivation of Tissues from Amphibians, by John C. Johnson.
eae Ep. 55-62, 2 figures in text, November, note hs pee POs ee ee ae

Reptiles of Southeastern California in the Vicinity. of the Turtie ~
“Mountains, = by ‘Charles: ‘Lewis Camp. Se 503-544, plates 19 22, :

“ol. 18, 1. The Schizopods; of the San Diego Weeiti, by Calvin Oo. Esterly, Pp. es

Gir, - phora ofthe San Diego Region, by Calvin 0. Esterly, Pp 21-38.

: oe : BELA a A 0 TEE ean ae BE Se as SO OR ee es :
Z &. The Vertical Distribution and Movements of the ‘Bchizopoda of the:

‘Fran Daniel, “Bp. 147-166, plates 8-9, 4 text figures. May 23,
7%, The Movements and Reactions of the. Isolated Melanophores of the
<8. -Polychaetous Annelids of the Pacific Coust in the Collections of the ©

11. A Study of the Structure. of Feathers, with Reference to their Taxo-

‘Gopher and Other Rodents, by Charles Daniel Holliger. Pp. 447-.

Vol. 1, 1. A Report upon the Physical Conditions in San Francisco Bay, Based -

Ss * <- 2) On Giardia microti. sp. nov., from the. Meadow Mouse, by Charles

2.25

2.22

BC

~1.00

Re

10

" UNIVERSITY oF CALIFORN IA _ PUBLICATIONS —(Continued)_

6. Notes. on. the Tintinnoina. - 1, On the “Probable Origin of ee oe: &
_tiara Haeckel. 2. On Petalotricha entzi sp. nov., by. Charles Atwood)

See Se - Kofoid. Pp. 63-69; 8 figures in text. - December, 1915-23
fe 6. Binary. and. Multiple Fission in Hesamitus, by. oe suey.
«= =. plates 9-11.-— z

: = 7, On a New aichomonad Flagellate, Trichomitus parvus, from ie Intes- SS sie:

. tine of Amphibians, by Olive Swezy. Pp..89-94, plate 12.
-_ Nos. 6 and 7 im one cover. “December, 1915. GLCP Sales a

8, On Blepharocorys equi sp. nov., a New Ciliate from’ the Gaecunt of tne.

‘Horse, by Irwin c. Schumacher. Pp. “85- 106, : “plate 13. Deconben

Sp AGT eg a ee ee er ee 2

8. Three New Helices from - California, ‘by s Stillman ‘Berry. “Bp. 107- ae

TTD Fa ALy LIL cs a eae ee ee te

- 10. On ‘Trypanosoma-triatomae, a New Flagellate from a Caeiyteran Bug ae
me from the Nests of the Wood Rat Neotoma fuscipes, by Charles Atwood —
- Kofoid and Irene McCulloch. Pp. 113-126, ‘Plates i4- 15. Seuruery, oe

RS 4 11. The Genera Monocercomonas oe Polyinastic, by Olive Sweay. 2p. 27- ae

*4183- plates 16-17, Fenruary, 1916, Se ee:

ey Notes on the Spiny: Lobster CP anaias interruptus) of. the Galiteenia Shoes
age Coast, by Bennet M. Allen. Pp. 189-152, 2 figs. in text. March, 1916 -.

= 18, Notes on the Marine Fishes of California, by. Carl L. Hubbs. Pp. 168-

169, plates 18-20." “March, 40162 ee ee re

“14. The Feeding Habits and Food of Pelagic ‘Copnepods and the ‘Question

“of Nutrition by Orgauic Substances in Solution in the Water, by oe

Calvin O. Esterly: Pp. 171-184, 2 figs. in text. “March, 1916 _ 2...

See ge ah phe Kinetonucleus. of Flagellates. and the. Binuclear, Theory of Hart- Sree ae
* mann, by Olive Swezy. Pp. 185-240, 58 figs. in text. March, 1916... 50

_ 16. On the Life-History of a Soil Amoeba, by: Charlie: Woodruff Wilson. ay
Pee ED 947-092. plates 18-25," July, 1916° 22.2 ee ee, | ee

~ 17. Distribution of the Land Vertebrates of Southeastern. ‘Washington, by ee,

Lee Raymond Dice. Pp. 293-348, plates 24-26. June, 1916...

Mecthe Aactomy. of Uepiuncias macular Whe Gudekeiok yk
Frank Daniel. © Pp. 349-370, pls. 27-29, s text. figures... ‘December, sao Se

: 1016 See rs ee a ee eee SOB 3

19. Some Phases of Spermatogenesis in the Mouse, by Harry B. Yocom. eee

=. Pp, 871-380, pl. 80.: January, Bo by Revie seater Gare er cng eee eer
90. Specificity in Behavior and the ‘Relation “Between - Habits” in ‘Natore.

and Reactions in the Laboratory, by Calvin 0. Esterly. EP. 881-392, av ee S
Maren sd 907s a eee ee ee Ree hts

21. The Occurrence of a Rhythn in® the. Geotropism of. Two Species. ot

“Plankton Copepods When Certain Recurring External Conditions are -

Absent, by Calvin 0. Esterly. Pp. 393-400. March, 191720 o..

-- 92. On Some ‘New. Species of: Aphroditidae from the Coast. of Galifornia, —

by Christine Essenberg. Pp. 401-430, plates 34-37, March, i6iy se Se eae

> 98. Notes on the Natural History and Behavior of Emerita analoga (Stimp- are

son),. by Harold Tupper. Mead. Pp. 431-438, i text figure. ne ey :

5 0 he se yen cee ieee IN es oe mines ee ony Ree oe Re Seen S Sie
ote -Ascidians of the Littoral Zone of Southern. California, by William E.

Ritter and Ruth A. Forsyth. Pp. 439-512, plates 38-46. Angust, 1917. 1.

: Vou: aT: 4, Diagnoses of Seven New Mammals from East-Central California, “by Sane

Joseph Grinnell: and Tracy_I. Storer. Pp. 1-8.

a, A New Bat of the Genus Myotis from the High Sierra Nevada of Cali- re

E: fornia, by Hilda Wood Grinnell. Pp. 9-10.

ae Nol i apd 2 in one covers “Auonst 1916 =
: 3. Spelerpes platycephalus, a New Alpine Salamander from the. Yosemite

National Park, - California, by Charles Lewis Camp. Pp. 11-14. Sep- Bese

Bie tep ti] eYsY Sd GS op Bas tip a Re SH a eR Cet op ere emer eer ee

4, A New Spermophile from the. San J See Valley, California, ‘with. uae

Notes: on Ammospermophilus nelsoni. nelsont Merriam, by.- Walter Be
Taylor. Pp. 15-20, 1 figure in text. October, 1916 2

5. Habits and Food of the Roadrunner in California, by Harold ©. “Bryant aS oe

ome Pp, 21-58, plates 1-4, 2 figures in text. -October, 1916 _-_. aS Sapam
6. Description of Biufo-canorus, a New-Toad from the Yosemite National Geist
Park, by Charlies Lewis Camp. = 59- 62,. 4 figures in text: Novem: oe

Neh eg WOR & Seas Bok oe Gf Ouse iui Sa Ren Sl Perens Nh Ore ances emote
-.7.-The Subspecies of - Sceloporis seeientae. ‘with Description of a New ngs
“Form from the Sierra Nevada and Systematic Notes on Other Cali- | -
aah fornia Lizards; by Charles Lewis Camp. Pp. 63-74. December, 1916 ~ .10
> 3, Osteological Relationships of ‘Three Species of Beavers, py F. HEV ES, :
“Holden, Pp. 75-114; plates 5-12, 18 text figures. March, 1917 2.0... os 40"
=< 9, Notes on the Systematic Status of the Toads and Frogs of California, Sen
py Charles. Lewis Camp. Pp. 115-125, 3 text figures. February, 1917.10
10. A- ‘Distributional List of the Amphibians and Reptiles of California, _-
by Joseph Grinnell and Charles Lewis. Sauk: on 127-208, 14 sigules es
< in text. July, 1917 ceeotenancnnentecentcetnoe Daehn sassacacasteceeerieeecenthceteoctscoeeeninacassessineesese Vege
Vol. 18, 1. Mitosis in Giardia Eye py William gc. Boeck, Pp. 1-26, “plate hs

“October, Seas eceesepsceneentteeeteees neta eee ec eer cneneec cence ec eeenenecnee cone cores eames ecteense <

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8. A New. Self-Regulating Paraffin Bath, by C. W. Woodworth. Pp. 89. : &%
425° 9 text- Ogres: April 1814-2 ee Se ee et oe

4, Diplodinium ecaudatum, with an Account of Its Neuromotor Apparatus, 5
by Robert G: Sharp....Pp. 43-122, plates 3-7, 4 text figures. May, — HER
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7. The Movements and. ‘Reactions of ‘the. ‘Tsolated ‘Melanophores of the
Frog, by 8. 3. Holmes, .Pp. 167-174, plate 10.. August, 1914 22.0. «10

&. Polychastous Annelids of the Pacific Coast in the Collections of the
Zoological Museum of ‘the University of California, by Aaron L.
Treadwell. Pp. 175-234, plates 11-12.

®. New Syliidse from San Francisco Bay (collected by the U. 8. 8.
** Albatross’”), by Aaron L, Treadwell. Pp. 235-238, 7 text figures.

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upon the Operations of the United States Fisheries Steamer ‘‘Alba- _
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Louderback, W. L. Schmitt, B. 0. Johnston. Pp. 1-198, plates 1-13, Shae os
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wing | acieneenetomrenateipannasd oe? aa

UNIVERSITY OF CALIFORNIA PUB ICATIONS —®
IN

ZOOLOGY
Vol. 18, No. 2, pp. 27-43 December 12, 1917

AN UNUSUAL EXTENSION OF THE DISTRIBU-
PON OF Tah SHIPWORM IN SAN
FRANCISCO BAY, CALIFORNIA

E BY
ALBERT L. BARROWS

CONTENTS

PAGE

Hinitieo Cie bomen dive C Kemi ile Gl eqme mG S) ee ece ree cess eee cre oe ce re eee se ee ne eee eS 27
General distribution of Xylotrya in San Francisco Bay .......----.--:--------------<----- 28
Recentuncursionkbor Aylotmya ato San Pablo Bay: 222 ceecc-ceeaceseee cece eeeree eee 29
ANC eS ats PBEM LT Cee ooo a cata Be acac eee conde vanctianncdsa voeessapeness tay -teperelets. Soeanoee 29

Wal air faim eas (nO Cet bees eee ence oe ce 5 oa con oe ae cab en abedcb a cateen tases menses Ee nee weeds aaa 30

AWW aero iy OE Ta ees aE RSE A ee ee Sy ee 31

TEA ASCE | COI GL IG HANS TH ASA 1 24) oh Gg SE 7 cae ee eee Re See A ere 31
Dischargvesoie treshe water into) Sam Pablo) Bay, seen eee 31

SEU DIAM? COLE (Seana, «| EP ol aye 1 Se yee aa re nee ee 33
Hemperature-condriions) im) Sam) Pablo! Baiy: 2cesc-cnceeseceeeeee sees 36

LRGUEWE TOE, ONE CO PLONLP ILO A Hoy TEFEN It 0 7s A ee a pee eee 36
(CUO W SHON NS) gO oe Se ete eee uP nn eee eee 4]
BES fo Mit co orned 10 anya eas oe eee ee ec wae 2S ake dBc adh SEE ce ee ee Pe 43

INTRODUCTION AND ACKNOWLEDGMENTS

It is said that the shipworm was unknown in San Francisco Bay
in the early history of the port, and that wood-boring molluses did
not become an extensive menace to marine woodwork here until some
years after the great increase in the shipping entering the bay which
followed upon the discovery of gold in California. Be that as it may,
a species of the Teredidae, Xylotrya setacea Tryon, now thoroughly
infests the main portion of the bay, and, as in other localities where
shipworms are abundant, this borer is a constant cause of damage to
marine timbering in this port. Another species of shipworm, 7'eredo
diegensis Bartsch, has also recently caused damage in the upper part
of San Francisco Bay.

28 University of California Publications in Zoology [ Vou. 18

For much of the material presented in this paper I am indebted
to engineers of several construction and transportation firms of San
Francisco and to engineers of the Union Oil Company. I wish also to
acknowledge the great courtesy of officers of the Corps of Civil Engi-
neers, United States Navy, stationed at the Mare Island Naval Station,
in furnishing information upon damage caused by marine wood borers
in wooden dikes about Mare Island. |

GENERAL DIstTRIBUTION OF SHIPWORMS IN San Francisco Bay

The part of San Francisco Bay in which shipworms are most
active, to judge from their destructiveness, lies in the regions nearest
the Golden Gate, where presumably not only the salinity of the water
is most favorable, since it most nearly approximates that of the open
sea, but where a suitable food supply of plankton is abundantly
brought in from the ocean with the tides.

Engineers familiar with conditions in this bay have reported a
certain falling off of the activity of shipworms in parts of the bay at
some distance from the Golden Gate, and particularly in those regions
where water from the open sea is not brought abundantly by the tides.
Thus along the North Beach wharves of San Francisco, in the vicinity
of Sausalito, in Racoon Strait, and about Angel Island and Alcatraz
Island, shipworms are extremely active. Unprotected timber in these
places is destroyed within a few months. On the Oakland side of the
bay, however, the rate of devastation of marine woodwork by ship-
worms is said to be slower than in the localities just mentioned, and
in the Oakland estuary the rate of activity of the borers is greatly
diminished, unprotected marine woodwork being said to last from two
to four years.

In these localities where the destructiveness of the shipworms is
thus decreased, it is usually found that the size of the borer is also
reduced from a diameter frequently of one-half inch for borers taken
from the Golden Gate to a diameter of one-eighth inch or three-six-
teenths inch for borers taken from parts of the Oakland estuary. In
localities where the activity of shipworms is reduced, the crustacean
wood-borer Limnoria is often increasingly destructive. Thus Lim-
nora seems here to be the more active in brackish water and teredine
wood-borers more active in normal sea water.

Shipworms are conspicuously absent in San Francisco Bay from
stagnant regions and from regions which are contaminated by sewage
or by factory or refinery wastes. Except in a few such regions, prac-

1917 | Barrows: Shipworm in San Francisco Bay 29

tically all of the timbers used in marine woodwork in the main part of
the bay are impregnated with creosote as a protection against ship-
worms as well as against Limnoria.

The northern portion of San Francisco Bay is called San Pablo
Bay, and is separated from the main part of the bay by San Pablo
Strait. It is generally believed that shipworms do not live in San
Pablo Bay because of the reduction of the salinity of the water in this
bay by the influx of a large amount of fresh water from the Sacra-
mento and San Joaquin rivers emptying into the bay through Car-
quinez Strait. In spite of prolific activity on the part of shipworms
in the main part of San Francisco Bay, the records of the Mare Island
Naval Station, in the upper part of San Pablo Bay, do not mention
the presence of marine wood-borers, either Xylotrya or Limnoria, prior
to the discovery of shipworms in the Mare Island dikes in January,
1914. The experience of construction engineers in charge of numerous
wharves from Vallejo Junction to Port Costa, at the head of San
Pablo Bay, confirms this record for the practical absence of wood-
borers from this locality.

ReEcENT APPEARANCE OF SHIPWORMS IN SAN Pasuo Bay

Dikes at Mare Island.—Mare Island is located at the head of San
Pablo Bay, opposite Carquinez Strait, through which empty the Saera-
mento and San Joaquin rivers. Several wooden dikes have been built
in the channel which separates Mare Island from the mainland and
about the entrance to this channel in order to confine the currents and
prevent the filling up of the channel by the deposition of silt. The
longest of these dikes reaches southward into San Pablo Bay along
the edge of the main ship channel through the bay for a distance of
over 8000 feet, and is designed to prevent a back current in the shallow
northern part of San Pablo Bay from carrying sediments into the
shipping channel by which the naval station may be reached. In
view of the usual limitation of the range of shipworms below San
Pablo Bay, it occasioned great surprise when an examination of cer-
tain of these wooden dikes in January, 1914, showed extensive damage
from the borers. It was found that the greatest damage had been
done in the long dike which offered the first exposure to tide water
coming up the bay, though damage had been done also in two shorter
dikes at the entrance to Mare Island Strait.

In general the damage in the long dike was greatest on the side
which faced the ship channel, where the water is deepest and where

30 University of California Publications in Zoology [ Von. 18

it is presumed that the flood tide sweeps up the bay with the least
reduction in salinity from the normal salinity of ocean water. On the
back or western side of this dike damage was noted for only about
2000 feet from the outer end, while on the front or eastern side the
damage extended for over 6000 feet shoreward from the outer end,
indicating that the eastern or front side of the dike was exposed to
water suitable for the existence of shipworms, while the water eddying
over the wide mudflat behind the dike was largely unsuitable for
them.

In the damaged portion of the dike the operations of the borers
were more extensive in the brace piling, which extended out from the
sheet piling at an oblique angle, than in the sheet piling, suggesting
that a free circulation of water about the isolated brace timbers pro-
moted the greater activity of the borers in these timbers. Much of the
brace piling was more than half eaten through, whereas the shipworms
had bored hardly more than an inch below the surface of the wood in
the sheet piling. Further, the greatest damage in these dikes was
found near the mudline, suggesting that the borers throve best in the
denser water known to lie along the bottom of the bay. The species
of shipworm in this ease has been identified as Teredo diegensis
Bartsch, by Dr. Paul Bartsch, of the United States National Museum,
to whom I am indebted for this courtesy. It is a small species making
holes averaging one-eighth or three-sixteenths inch in diameter.

The board of naval engineers which inspected the Mare Island
dikes on the occasion of this damage reported that this unprecedented
incursion of T’eredo was due to an increase in the salinity of the water
of that part of San Pablo Bay on account of the occurrence just
previously of two dry years in succession in which not only was the
rainfall and snowfall over the Sacramento-San Joaquin watershed
less than usual but in which it was so distributed that the amount of
runoff in proportion to the precipitation was also less than usual.

A repetition of damage to marine woodwork in this region, due
to Teredo, was found in January and February, 1917, when sample
piles showing renewed activity of Teredo were removed from a num-
ber of places in the outermost dike of the Mare Island Naval Station.
The penetration of the Teredo in these cases was generally not over
three inches in depth and the extent of damage caused at this time
was not so great as that during the incursion of 1913-14.

Wharf near Crockett—Another instance of damage due to ship-
worms in this vicinity came to light when in the spring of 1914 a

1917] Barrows: Shipworm in San Francisco Bay aL

freight steamer, on attempting to make fast to a wharf about a mile
above Vallejo Junction at the entrance of Carquinez Strait, rammed
the wharf and carried away a number of piles. A pile pulled up for
examination when this damage was repaired showed that the broken
timbers had been weakened by the operations of shipworms. At
Crockett, less than a mile above this point and well within Carquinez
Strait, untreated piles are still in use which are known to have been
in place for twenty-eight years.

Wharf at Olewm.—Damage due to wood-borers was also discovered
in a third locality in this same general region when repairs on the
wharf of the Union Oil Company at Oleum, less than a mile below
Vallejo Junction and directly opposite the long Mare Island dike
across the ship channel, revealed operations of wood-borers, the piles
of the wharf being corroded by the shipworms for a depth of about
one inch.

It thus appears that at three points located .within two or three
miles of each other at the head of San Pablo Bay notable damage was
done during 1912 and 1913 by a dwarfed race of shipworms, Teredo
diegensis Bartsch, in a region in which shipworms had not been
known to cause damage previously, and that renewed activity of these
borers was observed in the spring of 1916 and in the winter of 1916—
1917, in the same region. The fact that the damage reported occurred
at the head of San Pablo Bay may be explained probably by the
location of most of the untreated marine timbering in this bay near
the entrance to Carquinez Strait.

PHYSICAL CONDITIONS IN SAN PasBio Bay

Very fortunately for our present purpose definite information is
available upon the physical conditions of the waters of San Francisco
Bay (Sumner et al., 1914). This information ineludes observations
upon the temperature and salinity of San Pablo Bay made during the
two years preceding that in which the damage just described took place.

Discharge of Fresh Water into San Pablo Bay—Though a number
of small streams empty into San Pablo Bay besides the Sacramento
and San Joaquin rivers, by far the greater amount of fresh water
entering the bay comes from these two large rivers, both of which
empty into the bay through Carquinez Strait. The approximate
amount of fresh water discharged from the Sacramento-San Joaquin

BPA Unversity of California Publications in Zoology [ Vou. 18
river system for a series of ten years has been computed for the bio-
logical survey of San Francisco Bay (Sumner, et al., 1914, p. 77) by
a summation of the measured flow of the principal tributaries of this
system. Through the courtesy of Mr. H. D. MeGlashan of the United
States Geological Survey, who has furnished data for the years 1911-12
to 1914-15, it has been possible to complete these data for the years
of the survey, and also for the two following years. Though not rep-
resenting absolutely the total amount of fresh water passing through
Carquinez Strait from these rivers, these data, compiled according to
a uniform method for the fourteen years represented, furnish at least
a fairly accurate picture of the relative variation above or below the
average in the discharge of these rivers.

It is to be noted from the table below for the annual discharge
from the Sacramento-San Joaquin river system that the years 1912
and 1913 were both years of unusually small discharge, the runoff
amounting to less than half the average amount for the fourteen
In the season 1913-14,
however, the discharge of fresh water was over 22 per cent more than

years for which acceptable data are available.

the normal amount.

DISCHARGE OF SACRAMENTO AND SAN JOAQUIN RIVER SYSTEMS

In AcRE-FEET, BASED UPON ReEcorDS For FOURTEEN YEARS*

* Care has been taken to complete this table according to the same method as that employed
by Sumner in compiling the data for the years 1878-79 to 1910-11 inclusive (Sumner, et al.,

1914, p. 77).

Sacramento San Joaquin Combined
Year? system system flow

1878-79 26,387,000 7,090,000 33,477,000
1879-80 32,300,000 12,091,000 44,391,000
1880-81 32,000,000 9,916,000 41,916,000
1881-82 25,300,000 8,367,000 33,667,000
1882-83 17,800,000 6,361,000 24,161,000
1883-84 29,900,000 13,212,000 43,112,000
1907-08 15,291,000 4,023,000 19,314,000
1908-09 33,756,000 11,178,000 44,934,000
1909-10 20,705,000 8,106,000 28,811,000
1910-11 27,906,000 14,460,000 42,366,000
1911-12 11,372,000 3,797,000 15,169,000
1912-13 12,850,300 3,464,400 16,314,700
1913-14 31,442,000 10,366,000 41,808,000
1914-15 26,663,000 7,873,000 34,536,000

Average, 24,548,000 8,593,200 33,141,200

2 The runoff year is computed from October 1 to September 30.

1917 | Barrows: Shipworm in San Francisco Bay 33

The average monthly discharge from this double river system,
which of course varies with the rainfall and melting of the snow over
the watershed of the rivers, is given as follows (Sumner, et al., 1914,
p. 78):

MEAN MONTHLY DISCHARGE OF SACRAMENTO AND SAN JOAQUIN
RIVER SYSTEMS

BASED Upon ReEcorps For TEN YEARS

Runoff in

Month acre-feet
October 527,356
November 748,586
December 1,352,997
January 3,728,103
February 3,453,295
March 4,710,754
April 6,137,662
May 6,467,948
June 4,854,338
July 2,027,965
August 766,125
September 490,364

Total, 35,275,493

The months of maximum discharge of fresh water are seen from
this table to be April and May, and it is during these months that we
should expect the salinity of San Pablo Bay to be at its minimum.
The months of least discharge of fresh water are the fall months of
August, September, October, and November, and it is during these
months, constituting one-third of the year, that we should expect the
salinity of this bay to be at a maximum. ‘The seasonal increase in
the amount of fresh water discharged and the corresponding decrease
in the salinity of this part of the bay begins during December and
becomes marked during the month of January. It is to be noted in
this connection that shipworms were found dead in the later part of
January, 1914, in certain test piles which had been taken up early in
the month and moored for a few weeks alongside the dike which had
been infested with the borers. This may have been due to the influx
of a large amount of fresh water into this part of the bay during
that month as the first of a discharge of considerably more than even
the normal amount for that month during the rainy season of 1913-
1914, or possibly to heavy jarring of the pile when removing it.

Salinity of San Pablo Bay.—F rom this varying discharge of fresh
water into San Pablo Bay it has been found, as was expected, that the

34 University of Califorma Publications in Zoology [ Vou. 18

salinity of the water of the bay was greatest during the fall months
and least during the spring months. This is shown in the appended
table of salinity measurements for three stations chosen at the head
of the day and not far from the places where the Teredo had caused
damage.

These stations may be described as follows (Sumner, et al., 1914,
pedi5a. pl. 4)

Station 4975. Tang. Crockett Whf., S 74° E; Carquinez St., N 50° W;
Tang. Selby Whf., S 69° W. Well within the entrance to Carquinez Strait, near
Crockett; depth 1414-12 fms.

Station 4976. Tang. Crockett Whf., S 76° E; Carquinez St., S 48° E; Mare
Isl. St., N 27° E. In the middle of the ship channel, directly south of the south-
eastern end of Mare Island, and near the long dike; about 1 mile W by N from
Station 4975; depth 101%4-9% fms.

Station 4977. Carquinez St., N 71° E; Lone Tree Pt. Whf., S 36° E; Pinole

Pt. Tang., S 531%4° E. In the middle of the ship channel and about 1144 miles
W by 8 from Station 4976; depth 534-5 fms.

In the following tables, compiled both for salinity and temperature
from the published results of the biological survey of San Francisco
Bay, ‘‘the ‘surface’ figure is the mean of the surface figure recorded
during the flood-tide observation and that recorded during the ebb-
tide observation. Similarly, the ‘bottom’ figure is the mean of the
ebb and flood figures for the bottom’’ (Sumner, et al., 1914, p. 28).

SALINITY AT STATIONS IN UPPER SAN PABLO BAY

Parts PER THOUSAND
Station 4975 Station 4976 Station 4977
A ——A- ———

——.

Surface Bottom Die Surface Bottom Surface Bottom. Diff.
Feb. 13-27, 712 OA GSO oslo Uses} Weiss sil 13.23 19.71 6.48
Apr. 23—May 6 9.95 13.35 3.40 12.45 14.29 1.84 9.08 10.89 1.81
July 22—31, 712 12.55 16.74 4.19 ES eel alee G Woz 540) altsts}
Oct. 7-12, 712 17.40 19.14 1.74 16.93 18.99 1.16 20.538 22.55 2.02
Nov. 23—Dee. 5 13.82 18.89 5.07 14.18 17.82 3.64 43) Boece) eo.
Jan. 13-28, 713 12.48 17.30 4.82 14.00 15.92 1.92 14.84 20.27 5.43
Annual range, Utor SOng9) ws ysis) Giyskl) EA ale
Av. for entire year, 13.21 17.27 4.06 14.23 17.16 2.93 15.46 19.25

SS
Diff

From this table for salinity it appears that of the six periods of
observation the greatest salinities at all three stations were observed
both at the surface and at the bottom during the period October 7-12,
1912. This period corresponds in general with the period of least
discharge of fresh water from the Sacramento and San Joaquin river
system, and lags only a little behind the month (September) in which
the average minimum monthly discharge is found to oceur.

1917 | Barrows: Shipworm in San Francisco Bay 30

On the other hand, the lowest salinity observed occurred for all
stations, with one exception, during the period April 23—May 6, 1912.
This, again, corresponds in general, as would be expected, with the
period of greatest discharge from these rivers, and precedes by only
a few weeks the month of maximum average monthly discharge.

The lag just observed between the time of observation of greatest
salinity at these stations and the month of minimum average discharge
and the precedence of the time of observation of the least salinity
before the month of maximum average discharge are probably to be
explained by the arbitrary selection of observation periods which
happened not to coincide precisely with the actual periods of greatest
and least discharge from the rivers. This minor discrepancy, however,
does not vitiate the general conclusions to be drawn.

In the following table (Sumner, et al., 1914, p. 83) the salinity, as
observed at ebb tide, 1.e., when it might be expected to be at a minimum,
on March 5 and 6, 1914, is compared with the salinity observed at a
corresponding period in 1912 for station 4975 and for station 4978,
which hes in the ship channel about two miles west by south from
station 4977, described above, and for station 4974, which lies below
San Pablo Strait and is some fourteen miles from station 4975.

COMPARISON OF SALINITY AT SELECTED STATIONS AND PERIODS
IN 1912 AND 1914

1912 1914
eee ey eee — IX =
Surface Bottom Diff. Surface Bottom Diff.
4974 17.47 21.47 4.00 * 24.65 24.65
4975 13.91 18.55 4.65 * Bist Uh Bali

4978 14.19 21.47 7.28 4.02 13.42 9.40

* “Surface samples from these stations gave chlorine percentages so low that the salinities
could not be obtained from Knudsen’s Hydrographic Tables. These samples have therefore
been regarded as nearly pure river water.’”’ (Sumner, et al., 1913, p. 83.)

A difference of from 9 to 15 parts. per 1000 is to be noted in the
salinity of this part of the bay between observations during the flood
seasons of these two years for which, as has been noted, the discharge
of fresh water from the Sacramento-San Joaquin system differed so
markedly. <A point of greater significance, however, is the reduction
of the salinity at station 4975 to practically nil at the surface and to
3.77 at the bottom during the flood season of the ‘‘wet’’ year 1914,
whereas during the corresponding flood season of the ‘‘dry’’ year 1912
the surface salinity remained fairly high, 13.91.

Though we have but the single observation for these stations in
1914, it is presumable that the low salinity indicated on this occasion

36 University of California Publications in Zoology [ Vou. 18

may have been so frequently repeated during the later months of the
flood season as the discharge of fresh water reached its height as to
have presented salinity conditions during a considerable portion of
the year which would be inimical to the life of Teredo.
Temperature Conditions in San Pablo Bay—Since the temperature
may in a general way be of influence in determining the rate of
activity of these borers, the following table is appended of temper-
atures taken at the same stations and at the same times as the obser-
vations for salinity. It is not presumable, however, that a difference
in temperature of less than a degree between the temperature at the
surface and at the bottom at these stations should be sufficient to cause
so marked a difference in the activity of the borers as has been noted.
A difference of average annual temperature amounting to 5° C or
more between this general region and some other region may, however,
be sufficient to cause a marked difference in the activity of marine
borers even if the same species of borer be present in both cases.

TEMPERATURE OF SELECTED STATIONS IN SAN PABLO BAY
IN DEGREES CENTIGRADE

Station 4975 Station 4976 Station 4977
(= T= Sef Ta F
Date Surface Bottom Diff. Surface Bottom Diff. Surface Bottom Diff.

Feb. 18-27, 712) 9 12:18 12.16 02 12.24 12:27 303°. dZ.b2° 1ai8v le
Apr.23-May6 14.24 13.87 .387 13.74 13.78 .04 13.66 13.67 .01
July 22-27, 712 12.82 18.81 .01 1846 18.54 .08 19.10 1851 .59
Oct 7-12) 72 16.66 16.34 .32 16.63 18.54 14 1652 16.28 .24
Nov: 25-Dee.5. 11.55 173.18 1146 10-66 220 12.02) 19595 5207
Jan. 13—28, 713 5.96 6.35 .39 5.96 6.10 -14 6.34 6.63 .39
Annual range, 12586). W246. l2b0y 244s ee 2 6) ES Sage ee
Av. for entire year, 13.15 13.14 ... 13.04 13.08 ... 13.34 9 13.23 11

RELATION OF TEREDO TO SALINITY

It remains now to determine as closely as possible from these data,
so fortunately available, approximately the conditions of salinity which
seem to be required by this species of Teredo.

The lowest surface salinity observed at any of these stations during
1912 and 1913 was 9.08 parts per 1000 and the lowest bottom salinity
was 10.89, both observations occurring during the period April 23-
May 6 in the season of maximum discharge of fresh water for that
year. While we do not have the actual observations upon the salinity
at these stations for the full year 1913, it is presumable, since the total
discharge of fresh water was about the same for both years, 1912 and
1913, that the salinity could not have fallen much lower at any time

1917 | Barrows: Shipworm in San Francisco Bay 37

during the year 1913 than it did during the year 1912, for which we
have observations.

While it is not definitely known whether shipworms began their
disastrous operations in San Pablo Bay in 1912 or in 1913, there are
certain considerations which indicate that the primary infection by
the borers in this attack may have occurred in the summer and fall of
1912, with probably a second infection following upon the breeding
season of the following year. The breeding habits of certain species
of shipworms have been observed by Sigerfoos in Chesapeake Bay,
including Xylotrya gouldi Jeffreys and Teredo dilatata Spengler,
which are very abundant there, and Teredo navalis Linnaeus, which
occurs in that locality but rarely. Sigerfoos (1908, pp. 195-198)
writes as follows concerning the spawning habits of these species:

T. navalis retains its eggs in the gills during their embryonic development. .
On the other hand . . . the eggs of the other two species are laid free into and
fertilized in the water... .

In association with their character of free development in the water, the
eggs of the shipworm are very small and very numerous. While they vary
somewhat in size, they have an average diameter of somewhat less than 1/20 mm.
(1/500 inch). . . . In one case I estimated the number laid by a large female of
T. dilatata to be one hundred millions. . . . Development is very rapid and on
warm days the embryos become free-swimming within three hours after the
eggs are laid. Within a day the shell has been formed and the typical lamelli-
branch veliger stage has been reached... .

. .. What becomes of the larvae after hatching from the eggs, how and
where they live, it is difficult to surmise. Though the developed larvae are
settling on wooden structures constantly, I have not taken them and the inter-
mediate stages in the tow-net, and where they develop I do not know. The
rate of growth of larvae of the marine lamellibranchs, however, is slow, and I
think the larvae of shipworms when they attach themselves must be at least a
month old. They may be more, for at this time their development is quite
advanced and their organization complex.

The breeding season of X. gouldi and T. dilatata seems to extend throughout
the warm season. I have found ripe sexual products of both species from early
in May till the middle of August. At the latter time there seemed no abatement
in their development. . . . Individuals become sexually mature in a month after
they have attached, and those which attach in August must bear ripe sexual
products later in the season, so that the breeding period would seem to extend
throughout the warmer months. . .

The shipworm in its larval stages develops slowly, but once in the wood it
grows with remarkable rapidity. ... The newly attached larva is somewhat
less than 0.25 mm. long. In 12 days it has attained a length of about 3 mm.;
16 days, 6 mm.; 20 days, 11 mm.; 30 days, 63 mm.; and 36 days, 100 mm. In a
month specimens may contain ripe sexual products, though normally these seem
to be retained till Jarger quantities of spermatozoa and eggs are stored for
extrusion at one time.

38 University of California Publications in Zoology [ Vou. 18

Sumner (Sumner, et al., 1914, p. 55) gives the following comparison
of the mean annual temperature of San Francisco Bay with that of
the lower third of Chesapeake Bay, both bays being located in about
the same latitude:

Mean Range
San Francisco Bay 12.91°C 8.35° C
Chesapeake Bay 14:38°C! 22.12°°C

Although it is possible that the species of shipworms found in
Chesapeake Bay may not be able to live in San Francisco Bay because
adapted to the particular conditions of the Chesapeake Bay, in the
absence of definite knowledge of the breeding habits of the species
found in San Francisco Bay we may assume that there is no very great
difference in the general breeding habits of these two species. If
there be any difference we may expect that in San Francisco Bay,
where the temperature must fall off the less rapidly in the latter part
of the year, the breeding season of the Pacific Coast species of ship-
worms may continue later than that of the Atlantic species, and that
ege-laying may possibly begin earlier in the spring in San Francisco
Bay than in Chesapeake Bay. The period of possible infection of tim-

ber on the Pacifie Coast may therefore be longer than on the Atlantic’

Coast. Thus, it is not improbable that even in normal years Teredo
larvae may be carried from the main portion of San Francisco Bay
into San Pablo Bay by the tides of the late summer, and that they
may acquire at least a temporary foothold in accessible submerged
timber. It should be born in mind, however, that thé data for rate
of growth given by Sigerfoos are for shipworms living in that part of
Chesapeake Bay where the salinity is not greatly reduced, and that
these rates should therefore be compared with the rate of growth of
shipworms in the main part of San Francisco Bay rather than with
the supposed rate of growth of the shipworms found in San Pablo Bay.

The general conditions throughout a normal year at these localities
in the upper part of San Pablo Bay seem to include a period in which
the surface salinity, at least on certain tides, must be reduced to
practically zero and the bottom salinity to but a few points above zero.
Such a condition, which may be of annual recurrence in this vicinity,
appears to be sufficient to kill all shipworms which may have taken
‘hold of marine timber in these localities. This condition of greatly
reduced salinity in the spring, moreover, probably obtains during an
average year during so great a portion of the year as to effectually
prevent the existence of shipworms long enough to do notable damage,

1917 | Barrows: Shipworm in San Francisco Bay a9

even if they should become attached to woodwork during the season
when the salinity is high. If any larvae are brought up alive from the
lower portion of the bay after the flood season and do become attached,
they must usually be killed within a few months by the recurrence of
the next flood season. Adult shipworms embedded in the wood might
occasionally be able to endure the reduced salinity of a single ebb tide
by tightly closing the entrance to their bore, as they are able to do,
but they could not endure prolonged reduction of salinity.

On the other hand, the increased salinity of the water of San
Pablo Bay during a year of unusually small discharge of fresh water
from the Sacramento-San Joaquin river system may be such as to
permit not only the continuance of living Teredo in this bay through-
out the entire year but also much damage on account of increased
numbers and activity of the borers under the conditions of increased
salinity.

It is just possible that an infection of marine timber in the upper
part of San Pablo Bay may have occurred in the fall of 1911, and
that the shipworms entering the wood then may have continued to live
through the months of minimum fresh-water runoff in the winters of
both 1911-12 and 1912-13, and until the discovery of the damage
found in December, 1913; but so early an infection seems improbable
because the discharge of fresh water during the previous year was
nearly 28 per cent more than the average annual discharge.

It seems on the whole more probable that the first infection of the
attack in question occurred in the summer of 1912, because the falling
off of the discharge of fresh water unusually early in the spring of
that year must have lengthened the summer period during which San
Pablo Bay may have been open to invasion by Tcredo larvae, per-
mitting thus an unusually heavy infection to gain a foothold. If this
infection occurred then, the shipworms settling at that time must have
been able to withstand a reduction of salinity of about ten parts per
thousand during the spring freshets of both 1912 and 1913. Another
infection in the breeding season of 1913 may have caused an acceler-
ation during the fall of that year in the damage being done to the
structures attacked.

The lowest surface salinity recorded during 1912 was 9.08 parts per
1000 and the lowest bottom salinity 10.89. The average annual surface
salinity for the three stations referred to in the upper part of San
Pablo Bay ranged during the period of observation from 13.21 to
15.46 parts per 1000 and the average annual bottom salinity from

40 University of California Publications in Zoology [ Vou. 18

17.27 to 19.25 parts per 1000. It seems probable, therefore, that
Teredo diegensis, once established, can withstand for several weeks or
perhaps months a reduction of salinity to about 10 parts per 1000,
though perhaps thriving sufficiently to cause marked damage only
in a region where the salinity of the water, except for a short period,
must average at least 13 or 14 parts per 1000.

In common with a recognized biological principle, the adult ship-
worms, moreover, may be expected to be hardier and more resistant
to adverse circumstances than the larvae. Thus the larvae might be
able to invade San Pablo Bay only in the period of maximum salinity
in the bay during the late summer and fall, but once established and
developed into adult animals the shipworms might much better with-
stand the reduction in salinity of succeeding freshets of the winter and
spring, if this reduction should not fall below a certain minimum limit.

It is possible also that Teredo diegensis may breed normally in
localities where the salinity is lower than that which Yylotrya setacea
ean endure, and that damage to unprotected marine woodwork will
occur in such localities of reduced salinity from increased numbers of
native Teredo diegensis when, as oceasionally happens in San Pablo
Bay, a ‘‘dry’’ year permits the salinity to rise above the condition
usually prevailing. In this connection a more extensive knowledge
of the distribution of Teredo diegensis and of Xylotrya setacea in
such a region as San Francisco Bay than is at present available is to
be desired.

From the known rate of operation of shipworms of the small size
of those found in San Pablo Bay in other parts of San Franciseo Bay,
it seems hardly probable that the extensive damage to the brace piling
of the Mare Island dikes, in which many of the timbers were from
one-half to three-quarters destroyed, could have taken place during
the six or eight months following the falling off of the discharge of the
Sacramento and San Joaquin rivers in the summer of 1913. The
conclusion seems justified, therefore, that the damage reported in
January, 1914, dates back to an infection during the summer or fall
of 1912, at least a year and a half previously, but hardly to the fall
of 1911, two years and a half before.

The general observation of engineers in San Francisco Bay is that
the shipworm is much more active at or near the mudline than near
the tide levels. This same difference in the level of the greatest activity
of these borers was noted in the dikes of the Mare Island Navy Yard,
also in the piles extracted from the wharf of the Union Oil Company

1917 | Barrows: Shipworm in San Francisco Bay 4]

at Oleum. From the salinity table just quoted, the bottom salinity is
seen to be consistently greater than the surface density, in one instance
by as much as 6.48 parts per 1000. While Z'eredo diegensis will prob-
ably live in water of a salinity of 10 or 12 parts per 1000, a shghtly
greater density of a few points per 1000 seems directly or indirectly
to attract greater numbers of the borers and to stimulate their greater
activity. It is noteworthy that an average annual difference in salinity
of from 2.89 to 4.28 parts per 1000 within but a few fathoms of depth
should cause so distinct a difference in the abundance and activity of
these borers as has been reported.

It is probable that there may be a direct physiologic adaptation
between a certain degree of salinity and the wellbeing of these wood-
borers, such as is noted in the case of most marine animals, and which
effectually prevents their existence in water of either unusually low
or high salinity. It is possible also that the relation of shipworms to
salinity may be only an indirect one, and that the distribution of
shipworms may be at least partly dependent upon some other cause,
such as the presence of certain classes of plankton organisms, upon
which the shipworm may feed to the best advantage, which are in
their turn directly dependent upon water of a certain density for
flotation or of a certain salinity for their own physiologic wellbeing.

That Teredo diegensis is extremely sensitive to the amount of
water in circulation around the place where it may have settled ap-
pears from the fact that the damage to the Mare Isiand dikes was
much greater in the brace piling, consisting of isolated timbers set
at an angle away from the dike wall, than in the sheet piling which
formed the face of the wall, although both the brace piling and the
sheet piling were more or less infected for their full length. The
water washing more freely around the isolated brace timbers than
over the closely set sheet piles of the wall of the dike probably brought
to the borers in the brace piling a much more abundant supply of food
than to the borers located in the sheet piling, thus suggesting the close
ultimate relation between boring activity and food supply.

CONCLUSIONS

1. It, therefore, appears that shipworms of the species, T'eredo
diegensis Bartsch, may be intermittent residents of the vicinity of
Mare Island near the mouth of Carquinez Strait; that the excessive
damage caused by these borers in 1913 came about through the

42 University of California Publications in Zoology [ Von. 18

marked increase in the average salinity of the water of this part of
San Pablo Bay, because of the comparatively small amount of fresh
water which entered the bay during the two consecutive dry seasons
of 1910-11 and 1911-12; that these borers may be killed off entirely
by a season of unusually heavy rainfall, though a re-injection may
occur during the next summer and fall; and that these borers may
occur in this region in small numbers even in years of average rainfall.

2. A salinity of at least 10 parts per 1000 (approximately) seems
to be required for the existence of Teredo diegensis at temperatures
ranging from 6° to 19° C.

3. Damage may be expected at these temperatures from Teredo
diegensis in regions where the average annual salinity is as much as
13 or 14 parts per 1000, provided that the salinity does not fall for
any considerable period below 10 parts per 1000.

4. An increase in salinity of even 3 or 4 parts per 1000 above the
minimum salinity tolerated by Teredo diegensis seems to be effective
in considerably increasing the abundance of the borers and in stimulat-
ing their activity; hence their greater activity near the bottom than
near the surface in such localities as those under observation here.

5. The activity of Teredo diegensis is thus, directly or indirectly,
related to the salinity. It is possible, however, that the salinity itself
may not be the only factor determining the vertical or horizontal
distribution of these borers, but that some other condition may to a
certain extent be the factor immediately controlling this distribution,
such, perhaps, as the plankton food supply, which may be more deli-
cately related to the salinity than the shipworm is itself.

6. Of the several major factors of the marine environment, such
as temperature, salinity, depth, pressure, food supply, ete., salinity
may usually be regarded as the variable factor most likely to deter-
mine, either directly or indirectly, the distribution of Teredo diegensis
in bays where all these factors undergo greater variation than is
common on the open sea-coast.

7. Other things being equal, Teredo diegensis seems to be most
active in woodwork exposed to a good circulation of water; hence the
greater damage to the brace piling than to the sheet piling in the
Mare Island dikes. Thus, being apparently held in check by the
minimum salinity which ean be endured, the activity of Teredo
when once located in timber under tolerable conditions of salinity may
depend largely upon the amount of food material which the constantly
moving current may bring to it.

1917 | Barrows: Shipworm in San Francisco Bay 43

8. In such a bay as that of San Francisco, which is infested in its
main portion with shipworms, and in which the movement of the tide
is strongly felt in many parts, the borers may be expected to take ad-
vantage very promptly either of any variation in salinity which will
permit them to invade a previously unoceupied locality or of any
change in current conditions which by bringing in a more abundant
food supply than formerly will permit an increased rate of growth
and of destruction of woodwork.

9. This unusual occurrence of shipworms in the upper part of San
Pablo Bay is indicative not only of the avidity with which such an
organism seizes upon every opportunity to extend its distribution into
previously unoccupied localities but also of the great importance of
even slight and relatively temporary variations in conditions of the
environment in determining the limits of the distribution of the species,
particularly upon the fringe of its range.

10. It is noteworthy in this instance that Limnoria is not reported
to have invaded San Pablo Bay in company with Teredo diegensis,
though in other localities in San Francisco Bay, especially in those in
which the salinity is somewhat reduced, Limnoria constantly aecom-
panies the shipworms, and in certain places almost altogether super-
sedes them as a wood-borer, as, for example, in the Oakland estuary,
where conditions seem to be less favorable for the teredine borers.

Transmitted March 9, 1917.

BIBLIOGRAPHY
MOLL, F.
1914. (The shipworm; translation.) Naturw. Zeitschr. f. Forst-u. Land-
wirtsech., 12, 505-564, 12 figs. in text.
SicErFoos, C. P.
1908. Natural history, organization, and late development of the Teredi-
nidae, or shipworms. Bull. U.S. Bur. Fish., 27, 191-231, pls. 7-21.
SuMNER, F. B., LouDERBACK, G. D., Scumirt, W. L., and JOHNSTON, E. C.
1914. A report upon the physical conditions in San Francisco Bay based upon
the operations of the United States Fisheries Steamer ‘‘ Albatross’’
during the years 1912 and 1913. Univ. Calif. Publ. Zool., 14, 1-198,
pls. 1-13, 20 figs. in text.

ee ee ee

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A, Hecroerapite Plankton, and Dredging Records of the Scripps Instita-
tion for Biological Research of the University of California, 1901 to

1912, compiled and. arranged under the supervision of W. E. Ritter —

‘by Elits L. Michael and George. F. McEwen. Pp. 1 1-206, 4 text figures
yes Resi ced: see AA Pea otc L Ree wie Sip cee, BNE DENIC, SG a eae in ON Rea Spa UE DO
- 2, Continuation of Hydrographic, Plankton, and Dredging Records of the

Scripps Institution for Biological Reséarch of the University of Cali-

fornia (1913-1915), compiled and arranged under the supervision of

W. E. Ritter, by Ellis L. Michael, Zoologist- and Administrative ASs- .

sistant, George F. McEwen, Hydrographer. Pp. 207-254, 7 figures in

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California, 1908 to 1915, by George. F: a Nag tie wit ania Sey We

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Vol. 16, 1. An Outline of the Morphology and Life History of Grithidia lepto-
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“Kofoid. . Pp. 63-69; 8 figures in text. December, 1915 DIA a Nie Dias a ae

6. Binary and Multiple Fission in Heramitus, by Olive Swezy, Pp. 71-88,
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191 Benne pn ope ae SRB a ay gt SERA AE gy NS CA A AN gaa OCH OMG gis aA

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BET, ADUALYs SOLO 2S A Cae ee Ae Ses OAL

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from the Nests of the Wood Rat Neotoma fuscipes, by Charles Atwood
Kofoid and Irene McCulloch. Pp. 113-126, plates 14-15, -February,

SD Le ge RN ea ac aE IS Sgn uc eae SS theca ea ae ok nea SEES =x

11. The Genera Monocercomonas and Polymastiz, by Olive Swezy. Pp. 127-
1SS,,plates 16-17, “February, 19163 ose a eee
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15. The Kinetonucleus of Flagellates and the Binuclear Theory of Hart-
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16. On the Life-History of a Soil Amoeba, by Charlie. Woodruff Wilson.

: Pp: 243-299. plates 18-23; -Suly;, 1916 = ee SE
17, Distribution of the Land Vertebrates of Southeastern Washington, by
- Lee Raymond Dice. Pp, 293-348, plates 24-26. June, 1916...
18. The Anatomy of Heptanchus. maculatus; the Endoskeleton, by 3
Frank Daniel, Pp. 349-370, pls, 27-29, 8 text figures. December,
OE a es ie > So eg Se ccc ca eaaed Rega ea ce ee Scene ias
19, Some Phases of Spermatogenesis in the Mouse, by Harry B. Yocom.
A eee iD Di tar aos DL OUs) ADUAEY), LON by oe age ee a ae ee
20, Specificity in Behavior and the Relation Between Habits in Nature
and Reactions in the Laboratory, by Calvin O. Esterly.- Pp. 381-392.
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* Notes on Ammospermophilus nelsoni nelsoni Merriam, by Walter P..

; Taylor. Pp..15-20, 1-figure in text. October, 1916 —.02.02.00
5. Habits and Food of the Roadrunner in California, by Harold c. Bryant.
; Pp. 21-58, plates 1-4, 2 figures in text: October, 1916 20.200. :

6. Description of Bufo canorus,.a New Toad from the Voseniite National

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UNIVERSITY OF CALIFORNIA PUBLICATIONS
IN

ZOOLOGY
Vol. 18, No. 3, pp. 45-60, plates 2-3 October 17, 1917

DESCRIPTION OF SOME NEW SPECIES OF
POLYNOIDAE FROM THE COAST OF

CALIFORNIA
/< :
BY f.
5 oh
CHRISTINE ESSENBERG \
CONTENTS
PAGE
DEAN ETRY GUY CR EO ees SN ee en Sos tls SS eee 45
ANU SION A CSG UES TASS see eee eer ee en SS Sere eee 45
Generaladescriptionmotetlies Poly oielee ooo seas ce: ace ese oe nee eee angen see een 46
DESCRIP ULOMY Ol PNG Wa SPOOLS iecsceeseeec ees mea SE ey ak ES ee ecco 48
SUPP eAaysAaMOVe). || NOVAS KSHIST SY D5 ANON rece ee ea ear eee ere ne ace 48
EaTMO toe ey O MMS OMIha Ss Dee Ml OV re ese toa. wae <2 2 =-22 30 -a8ace conta coos saeseed ees pearance teats eats oaccnctsnce 50
Halosydna macrocephala, sp. MOV. ..........-..---------+---2c2--sneeeeceeeeteneteeceneecencnancerenntaccnenene 53
JOURS RADU RS) | LONE ssc cose ae ee Rn ey oe 56
EEXoTOL CATT ALT OTIN MO fag VEC Stas < estate cere esc ce bie cantare che udb bs cbacedeeenccee ee apnea eae eer os ctnteese 58
INTRODUCTION

In 1897 Dr. H. P. Johnson reported that there were thirteen
species of Polynoidae on the Pacific Coast. The number of species
has increased since that time to about fifty. The purpose of this
paper is to add to that list some species which have not been described
by any of the previous workers.

ACKNOWLEDGMENT
The work was carried on in the Zoological Laboratory of the
University of California. The writer wishes to express her sincere
gratitude to Professor Charles A. Kofoid for his interest and valuable
criticisms of this work.

46 University of Califorma Publications in Zoology [ Vou. 18

GENERAL DESCRIPTION OF THE POLYNOIDAE

The Polynoidae are widely distributed, occurring in boreal, tem-
perate and tropical zones; in shallow waters and in depths beyond
3000 fathoms. A few species are cosmopolitan, occurring in all
oceans, but for the most part each particular area harbors its char-
acteristic species; species common around San Diego Bay are not
found in San Francisco Bay, but their place is taken by other species.

The Polynoidae were classified by the early workers as a genus or
several genera of Aphroditidae. The recent workers, however, with a
few exceptions, are following Kinberg’s (1857) plan in classifying
the Polynoidae as an independent family. The Polynoidae resemble
the Aphroditidae in certain characteristics. In the first place, they bear
seales, or elytra, which are arranged in the same order as in Aphrodi-
tidae, occurring on segments 2, 4, 5, and on all alternate segments
to segment 23. Thence posteriorly the arrangement of elytra is less
regular. In the second place all elytroferous segments are devoid of
dorsal cirri. The peristomal segment bears the first parapodia. On
the other hand, the Polynoidae differ from the Aphroditidae in some
essential characteristics. The shape of the body of the Polynoidae
is more oblong than that of Aphroditidae, varying in length in dif-
ferent species. The lateral and the felt fibers are absent in Poly-
noidae. The parapodia are biramous and distinct from the main
body. The prostomium is bilobed and convex. The facial caruncle is
absent. The eyes, instead of being borne on peduncles, are placed
farther posteriad on the prostomial lobe. The base of the median
tentacle is inserted in the anterior fissure of the prostomial lobe.
Two additional lateral tentacles are present. The proboscis is mus-
cular and exsertile with a chitinous armature. The chitinous jaws
are strongly developed. The setae are of two or more kinds and are
more complex than those of the Aphroditidae. The nephridial papil-
lae open ventrally at the base of the parapodia.

The shape, size, and color of the body of the Polynoidae may vary
according to the conditions and the environment in which the indi-
viduals live. Hence these characteristics do not always furnish a
reliable basis for classification. The following may serve as an illus-
tration. While at the Seripps Institution for Biological Research at
La Jolla, I had opportunity to compare specimens of Polynoé pulchra
which had been taken from different hosts. The specimens that came

1917 | Essenberg: New Species of Polynoidae 47

from a holothurian, Stichopus californicus, were brown in color, while
the specimens found on the key-hole limpet Lucapina crenulata were
dark, with conspicuous black rings on the elytra. At certain times
the body of the worm may be filled with ova and greatly expanded,
giving the worm a different appearance. The elytra do not extend far
enough in that case to cover the entire dorsum.

However, some characteristics are constant, furnishing a reliable
basis for classification. Among these are the shape and the relative
size of the prostomium, the size and location of the eyes, the relative
length and structure of the cirri and of the palpi, the structure of the
setae, the shape and relative size of the corresponding parapodia, and
to some extent the number and structure of the elytra. The last
characteristic may not be true of long worms, such as Lepidosthenia
gigas. The number of elytra may vary in this ease in different
individuals.

The Polynoidae are voracious feeders, attacking one another when
in captivity. The writer had a number of specimens of Polynoé cali-
formca in an aquarium, where the food supply was scarce. The worms
attacked one another with their strongly developed jaws, displacing
the elytra or removing entire posterior segments of their companions.

The material used in this work was from the annelid collection of
the Zoological Museum of the University of California at Berkeley.
In the material of that collection some species were found that had
not been mentioned previously in Treadwell’s (1914) summary of the
polychaetous annelids of the Pacific Coast. These were: Polynoé com:
planata Johnson, which I found labelled Harmothoé imbricata, and
a number of specimens of Halosydna lagunae Hamilton, which
were labelled as Lepidonotus caelorus. Halosydna carinata Moore,
reported by A. Treadwell (1914) as being in the collection, was not
there; some specimens labelled Harmothoé carinata did not agree
with the characteristics of Harmothoé carinata. The writer had the
opportunity of comparing a specimen of Harmothoé carinata, which
Dr. J. P. Moore had the kindness to send to us, with the specimens
labelled Harmothoé carinata Moore, in the Zoological Museum at
Berkeley. Some EHunoe barbata were found labelled as Harmothoé
crassicirrata.

48 University of California Publications in Zoology [Vou. 18

DESCRIPTION OF NEW SPECIES

The species of Polynoidae in these collections were mostly well
known or previously described. The following species, Harmothoe
bonitensis, Harmothoé johnsoni, and Halosydna macrocephala, are
new.

Harmothoé bonitensis sp. nov.
: Pegs: de ;

Description—A rather small-sized polynoid; the 32 anterior seg-
ments measuring 25 mm. in length, and the width at the widest part
of the body, between the tenth and twelfth segments, is 5mm. The
dorso-ventral diameter is 1 mm. The worm is very much flattened
dorso-ventrally and rounded at both ends. The anterior parapodia
are shorter than those toward the central portion of the body. Thus
the anterior end appears narrower, increasing in width up to the
twelfth segment, where the maximum width is reached. The width
decreases then gradually toward the posterior end. The color of the
body is yellowish gray. There are only 32 anterior segments. The
extreme posterior segments are missing.

The prostomium (pl. 2, fig. 1) is deeply fissured, with prominent
acuminated peaks. The length of the prostomium is two-thirds of the
width. The four pairs of eyes are comparatively large. The anterior
eyes are situated in the widest part of the prostomium near the dorso-
lateral margin. They are pointed anteriorly and laterally. The
posterior eyes are smaller and are situated near the posterior end of
the prostomium. They are closer together medially, and look poste-
riorly and upward. The cirratophore of the median tentacle is promi-
nent, inserted between the prostomial lobes. The style of the median
tentacle is missing. In this specimen the short lateral tentacles arise
from short cirratophores, ventrad and mediad of the acuminated
peaks. Their length is about two-thirds that of the prostomium. The
palpi are white, stout at the base, decreasing in diameter very grad-
ually and terminating in fine tips. Their length is nearly five times
the length of the prostomium. They are densely covered with club-
shaped sensory cilia, which are arranged spirally. The cirratophores
of the peristomial cirri are long, equal in length to the prostomium,
but the styles are missing. The dorsal cirri of the other segments
(pl. 2, fig. 5) are white, of medium length, their tips extending to

1917] Essenberg: New Species of Polynoidae 49

the tips of the longest setae, covered with short, club-shaped papillae.
The ventral cirri are short and fusiform.

The parapodia (pl. 2, fig. 5) are biramous. Each ramus is sup-
ported by an aciculum. The ventral ramus is by far the more promi-
nent, forming a triangle and ending in a narrow projection. The
dorsal ramus or notopodium is less prominent, ending in a long,
finger-like projection, through which the aciculum projects.

The neurosetae are very numerous, 40 to 50, varying in size and
structure. The ventral-most setae (pl. 2, figs. 9 and 10) are the
shortest, about one-half the length of the long setae, with less con-
spicuous serrations. The setae increase in length and complexity
toward the dorsum. The long neurosetae (pl. 2, fig. 11) are slender
and the serrations are conspicuous. The ventral setae have a strong
subterminal tooth, and curved, pointed tips. The dorsal setae are
also very numerous (about 50 or more). In their arrangement they
give the appearance of a fan. They are arranged in six or more rows.
The ventral setae are the longest, being about three times the length
of the long notosetae, decreasing in length dorso-anteriorly. The
setae are curved, ending bluntly, their distal ends, except the extreme
tips, being covered with fine serrations, which are more pronounced
on the convex side. The postero-ventral setae (pl. 2, figs. 6 and 7)
are long and stout, about one-half the width of the body. The extreme
dorso-anterior notosetae (pl. 2, fig. 8) are very short, strongly curved,
with but a few serrations on the convex side. Between these extreme
dorsal and ventral setae all gradations of size occur. The color of the
setae is golden yellow. Their arrangement is such that in each suc-
ceeding row the setae curve in opposite directions. This arrangement
may be of some service as a protection for the animal.

There are fifteen pairs of elytra (pl. 2, figs. 2 and 3) covering the
greater part of the dorsum, except the narrow median line, which is
partly exposed. They occur on segments 2, 4, 5, and on all alternate
segments to 25; then on 26, 29 and 32. The first pair of elytra (pl.
2, fig. 2) are nearly orbicular; the rest are reniform. They are densely
covered with brown, spinous protuberances (pl. 2, fig. 4). These pro-
tuberances are club-shaped and covered with secondary projections.
Numerous soft, white projections are scattered over the elytra. These
projections are of the same shape as the marginal fringes, many
exceeding the latter in length. The marginal fringes are confined to
the postero-lateral margin only. A few large, soft tubercles are found
near the lateral margin of the elytra.

50 University of California Publications in Zoology [Vou. 18

Comparison.—A single example of this species is in the Zoological
Museum of the University of California. It bears some resemblance
to Harmothoé triannulata Moore (1910). Especially the shape and
structure of the elytra, as far as can be judged from figures and
descriptions of J. P. Moore, have a great resemblance. There is also
some similarity in the setae of the two species. There are, how-
ever, some characteristic differences in the general shape of the body,
the shape of the prostomium, of the cirri, and of other structures.
The body. of Harmothoé triannulata, according to Moore’s deserip-
tion, is deep, while in Harmothoé bonitensis it is very much flattened
and thin dorso-ventrally. The palpi are comparatively short and
smooth in Harmothoé triannulata, approximately less than three
times the length of the prostomium; in Harmothoé bonitensis the
palpi are long (about five times the length of the prostomium) and
are covered with spirally arranged rows of spines. The dorsal cirri
of Harmothoé triannulata are covered with more conspicuous spines
resembling more the cirri of Harmothoé hirsuta, while in Harmothoé
bonitensis the spines are inconspicuous. In Harmothoé triannulata
the notosetae are ‘‘moderate in number, forming an inconspicuous,
depressed whorl’’; in Harmothoé bonitensis, they are very numerous,
forming a conspicuous whorl (see pl. 2, fig. 3). The setae are some-
what similar in shape in both Harmothoé triannulata and H. boni-
tensis, except the short, strongly curved notosetae of Harmothoé
bonitensis (pl. 2, fig. 8) have no representatives in the figures for
Harmothoé triannulata given by Moore. The distal ends of the neu-
rosetae of Harmothoé triannulata are more slender and uniform in
diameter, while those of Harmothoé bonitensis decrease in diameter
gradually toward the tips.

Occurrence.—The specimen was found near Bonita Point at
Station D 5846 at lat. 89° N, in a depth of 45-50 fathoms in the col-
lection of the Survey of San Francisco Bay, made by the United
States Bureau of Fisheries, April 7, 1913. This description is pub-
lished by the kind permission of the Commission of the United States
Bureau of Fisheries.

Harmothoé johnsoni sp. nov.

Pl. 2, figs. 12-17; pl. 3, figs. 18-21
Description—The worm is flattened, but comparatively deep
dorso-ventrally, the depth of the body bemg 4 mm. The color in
the aleoholic specimen is gray. The dorsum is covered with large,

1917 | Essenberg: New Species of Polynoidae ik
widely overlapping elytra. The dorsal and ventral surfaces are con-
vex and the thirty-seven segments are well marked. The length of
the body is 35 mm., and the width, including the setae is 14 mm. in
the widest part of the body between segments 15 and 16. From these
segments the body alternates very gradually towards both ends, more
strongly towards the posterior end. The width of the body, excluding
the setae and parapodia, is about one-third of the entire width, the
length of each parapodium including setae being equal to the width
of the body, or the parapodia and setae make up two-thirds of the
entire width of the body.

The prostomium (pl. 2, fig. 12) is deep and broad; the length of
the prostomium being only about two-thirds of the width. It is
deeply fissured with acuminated anterior peaks. There are two pairs
of comparatively small and equal-sized eyes. The anterior eyes are
anterior to the widest part of the prostomium, while the posterior
pair are near the center of the prostomium, about two-thirds of the
distance from the anterior margin. The style of the median tentacle
is missing. The strongly developed cirratophore is deeply inserted
between the prostomial lobes. The lateral tentacles arise from
prominent cirratophores. The styles are very short, being only
slightly longer than the cirratophores. The leneth of the lateral
tentacles, including the styles and cirratophores is about one-third
of that of the prostomium. The palpi are stout and uniform in width
near the base attenuating very gradually toward the distal ends.
They are round and perfectly smooth without any papillae or cilia,
shghtly longer than the peristomial cirri.

The parapodia (pl. 2, fig. 14) are long, their length being equal
to the width of the body, biramous, each ramus terminating in a nar-
row, finger-like projection, and is supported by a strong dark brown
aciculum. The cirratophores of the dorsal cirri are very long, their
length being about one-third of that of the style. The latter decreases
very gradually in diameter toward the distal end, terminating in a
fine filamentous tip. The neurocirrus occurs on all segments and
consists of a strong cirratophore and a fusiform style.

The setae are numerous, from 70-100 on each parapodium. They
are distinctly of three kinds, with gradations between, in size, as
well as in structure. They are longest towards the center, decreasing
in length ventrally and dorsally. The neurosetae (pl. 2, figs. 16 and
17) are long and slender, the longest neurosetae being equal in length
to that of the parapodium and are twice the length of the stout noto-

52 University of California Publications in Zoology _[Vou. 18

setae. The subdistal end is covered with strong serrations, while the
slender extreme distal portion and also the greater part of the
proximal end is entirely smooth without any serrations. The extreme
ventral neurosetae (pl. 3, fig. 21) are very much shorter than are
those near the center, being about one-half or less the length of the
latter. They are strongly curved, with the fine distal end slightly
bent, and the convex subterminal portion strongly serrated.

The notosetae are of two distinct kinds. There are about half a
dozen or more of fine dorsal setae (pl. 3, figs. 19 and 20) near the
neuropodium. They are about equal in length to the long neurosetae,
curved, attenuating very gradually and ending in very fine, almost
capillary tips. The distal convex side is covered with spinous rough-
enings (pl. 3, fig. 20). The notosetae of the other kind are numerous,
arranged in rows, each row consisting of 6 to 10 setae thus making a
total of about 50 or more notosetae on each parapodium. The dorsal-
most rows contain the shortest setae. The length of the setae increases
with each succeeding row ventrad, until the maximum length is
reached in the last row nearest to the neuropodium, the setae there
being about twice the length of the shorter setae from the dorsal most
rows. The setae are stout, perfectly smooth without any roughen-
ings or serrations, uniform in width, tapering very abruptly towards
the distal end (pl. 3, fig. 18).

There are fifteen pairs of elytra occurring on segments 2, 4, 5
and on all alternate segments to 23, then on segments 26, 29, and 32.
The elytra (pl. 3, fig. 13) are kidney-shaped, large, widely overlap-
ping, and thickly covered with chitinous tubercles (pl. 3, fig. 15).
Fine venations radiate from the elytrophore in all directions.

The nephridial papillae begin with the sixth segment, occurring
thence posteriorly on all segments. They are short, inconspicuous,
and uniform in diameter.

Comparison.—The polynoid bears some resemblance to Harmothoé
complanata Johnson (1901), and might even be considered as a sub-
species of the latter. It differs, however, from Harmothoé complanata
in the shape, and the relative dimensions of the body, the shape and
the size of the prostomium, the shape of the parapodia and in the
structure of the notosetae. In Harmothoé complanata the breadth of
the body including the setae, is two-sevenths of the length, while in
Harmothoé johnsoni the breadth including the setae is one-third of
the length. The prostomium of Harmothoé complanata is equal in
width and length, in Harmothoé johnsoni the prostomium is decidedly

1917 | Essenberg: New Species of Polynoidae 53

broader, the length being two-thirds of the width. The parapodia
also differ in shape in the two species. In Harmothoe complanata the
dorsal ramus or the notopodium is very much shorter than the neu-
ropodium, having about less than one-half of the length of the neuro-
podium, while in Harmothoé johnson both rami are almost equal
in length (pl. 2, fig. 14). The stout dorsal setae of Harmothoé com-
planata are serrated, those of Harmothoé johnson are perfectly
smooth. The nephridial papillae in Harmothoé complanata have
acuminated tips; they are uniform in width ending abruptly in
Harmothoé johnsom. The color of Harmothoé complanata in the
alcoholic specimens is reported by Johnson (1901) to be pale brown
and a specimen in the Zoological Museum of the University of Cali-
fornia is also of a brown color, while the color of Harmothoé johnson
is light gray. The color, however, is not of great importance in classi-
fication.

Occurrence.—The single specimen which is now in the Zoological
Museum of the University of California, was given to the writer by
Mr. H. O. Falk, who had found it December 4, 1915, at a low tide
on the beach off La Jolla, near San Diego, California.

Halosydna macrocephala sp. nov.
Pl. 3, figs. 22-33

Description.—The shape of the body is flattened and uniform in
width, narrowing gradually toward the posterior end, rounded at
both ends. The two specimens are 40 mm. and 25 mm. long, and 10.5
and 7 mm. wide respectively, with 5 mm. between parapodia. The
dorsum is covered with widely overlapping elytra.

The prostomium (pl. 3, fig. 22) is unusually broad, the width
being more than twice the length. It is very convex, forming a deep
median fissure and sloping down abruptly on both sides. Of the two
pairs of eyes those of the anterior are considerably larger and are
situated near the lateral margins in about the widest part of the
prostomiums. The posterior eyes are smaller, nearer together, and
are situated at the extreme posterior margin of the prostomium, so
that they are partly concealed by the peristomial fold. The strongly
developed cirratophore of the median tentacle is inserted between
the anterior cephalic prolongations. The style of the median tentacle
is lost in both specimens. The stout lateral tentacles, arising from the
anterior prostomial prolongations are about one-half of the length

54 University of California Publications in Zoology Vou. 18

of the palpi. They are uniform in diameter with subterminal enlarge-
ments ending then in filamentous tips. The palpi are very stout at the
base, decreasing in diameter gradually and ending abruptly in
filamentous tips; they are deeply grooved and covered with rows of
prominent cilia. The peristomial cirri arising from strong cirrato-
phores are of equal length with the palpi. The styles of the peris-
tomial cirri are long, uniform in width, with subterminal bulb from
which filamentous tips project.

The biramous parapodia (pl. 3, fig. 25) are comparatively stout,
bearing two dark aciculi. The neuropodium has numerous (40-60)
amber-colored setae, varying in shape and size. There are about
twenty supra-acicular setae (pl. 3, fig. 30) with prominent serrations
and a strong subterminal tooth. The 30 to 40 subacicular setae (pl.
3, fig. 33) differ slightly from the supra-acicular in that the sub-
terminal tooth is smaller or rudimentary. The notopodium is incon-
spicuous and bears two kinds of setae; about 12 to 15 short, strongly
curved setae, covered with strong serrations and ending bluntly with
the proximal end and the extreme distal end smooth or free from
serrations (pl. 3, fig. 31), and about 20 to 30 long, fine setae, densely
covered with serrations, more or less curved and terminating in a fine
point (pl. 8, figs. 26 and 27).

The setae from the second parapodium differ from those of other
parapodia in their shape and also by being more strongly serrated.
The notosetae (pl. 3, figs. 28 and 29) are about equal in size to the
neurosetae (pl. 3, fig. 832). They are also nearly alike in shape and
structure.

The nephridial papillae begin on the fourth segment, being
situated at the dorso-lateral margin near the base of the parapodium
and occurring thence posteriorly on all segments. The first or
anterior papillae are short, increasing considerably in length dorsad.

There are eighteen pairs of elytra (pl. 3, fig. 23) oceurring on
segments 2, 4, 5, and on all alternate segments to 27, then on seg-
ments 28, 30, 31 and 33. They are comparatively thin and smooth,
with but a few small, scattered papillae and are mottled with dark
brown or black pigment (pl. 3, fig. 24). There are no marginal
cilia. Fine venations radiate from the elytrophore in all directions.
The dorsal cirri are equal in size and shape to the peristomial ecirri.

Comparison.—The species resembles Halosydna carinata Moore
(1903) in some respects and this is specially true of the broad pro-
stomium and the conspicuously grooved palpi. The chief difference

1917 | Essenberg: New Species of Polynoidae 5D

lies in the shape of the parapodia and in the number and shape of
the setae. In Halosydna carinata, of which Dr. J. P. Moore kindly
loaned to me an imperfect specimen for comparison, the notopodia
are small but prominent, being distinctly differentiated, while in
Halosydna macrocephala the notopodium is inconspicuous and hardly
differentiated. The neurosetae in Halosydna carinata are few, 10
to 20. They are strongly serrated, the plates with the serrations
extending to the tip of the subterminal tooth; in Halosydna macro-
cephala the neurosetae are more numerous, (40 to 60) the subterminal
tooth is less prominent and the serrations do not extend nearly to the
subterminal tooth, leaving a considerable portion of the distal end of
the setae smooth. The notosetae in Halosydna carinata are few, only
3 to 4, short, barely reaching to the tip of the notopodium, curved
and ending bluntly. In Halosydna macrocephala the neurosetae are
numerous, (30 to 40) of two kinds, and long, reaching nearly to the
tip of the neuropodium. The 12 to 15 short setae are strongly ser-
rated, curved, and end bluntly (pl. 3, fig. 31). The twenty or more
fine notosetae are covered with fine serrations and are terminating in
a fine capillary tip.

The setae of Halosydna macrocephala resemble those of Halosydna
californica, Johnson, but the shape and the relative size of the pro-
stomium and the deeply grooved palpi of Halosydna macrocephala
distinguish the species from Halosydna californica.

Occurrence.—The locality of the type is unknown. Two incom-
plete specimens, the paratypes were found July 17, 1901, off San
Diego, lat. 33° 369 N; long. 118° 14’7 W, at a depth of 39-51 meters,
on rocky bottom.

56 University of California Publications in Zoology [Vou. 18

LITERATURE CITED
HAMILTON, W. F.
1915. On two new polynoids from Laguna. Jour. Entom. Zool. Pomona, 7,
234-240, pls. 1-2.

JOHNSON, H. P.
1897. A preliminary account of the marine annelids of the Pacific Coast
with description of new species. Proc. Calif. Acad. Sci., (3) 1,
153-198, pls. 5-10.
1901. The Polychaeta of the Puget Sound region. Proc. Bost. Soc. Nat.
Hist., 29, 381-437, 19 pls.

KINBERG, J. G. H.
1855. Nya slagten och arter of annelider. Ofv. K. v. Vet. Akad. Forh.,
12, 381-388.

Moorz, J. P.
1910. The polychaetous annelids dredged by the U. 8S. S. ‘‘Albatross’’
off the coast of Southern California. Proc. Acad. Nat. Sci. Phila.,
62, 328-402, pls. 15-21.
TREADWELL, A. L.
1914. Polychaetous annelids of the Pacific Coast in the collections of the
Zoological Museum of the University of California. Univ. Calif.
Publ. Zool., 13, 175-238, pls. 11-12, 7 figs. in text.

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Fig.
Fig.
Fig.
Fig.

EXPLANATION OF PLATES
PLATE 2
Harmothoé bonitensis, sp. nov.

Prostomium. X 10.

Fifth elytron. X 10.

First elytron. X 10.

Portion of elytron. X 310.

Fourteenth parapodium. X 15.

Tip of long notoseta. X 310.

Tip of long notoseta. X 75.

Tip of short notoseta. XX 160.

Tip of short notoseta. X 75.

The same. X 310.

Tip of long neuroseta. X 310.

Prostomium. X 20.

Hifth elytron. X 10.

Eighteenth parapodium. XX 10.

Tubercles of elytron. X 160.

Portion of long neuroseta. X 310.

Tip of long neuroseta. X 75.

[ESSENBERG] PLATE 2

UNIVIN GALI RUBESZOOE VOEWI8

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PLATE 3
Harmothoé johnsoni, sp. nov.

Tip of short notoseta. X 310.
Tip of fine notoseta. X 45.
Portion of the same. X 310.
Tip of short neuroseta. X 160.

Halosydna macrocephala, sp . nov.
Prostomium. X 20.
Elytron. X 10.
Portion of elytron. X 75.
Fourteenth parapodium. X 10.
Tip of long notoseta. X 75.
Portion of the same. X 310.
Tip of notoseta of first parapodium. X 160.
Portion of the same. X 310.
Tip of supra-acicular neuroseta. X 160.
Tip of short notoseta. X 310.
Neuroseta from first parapodium. X 160.
Subacicular neuroseta. X 310.

[60]

[ESSENBERG] PLATE 3

UNIV. CALIF. PUBL. ZOOL. VOL. 18

essa xs eC C(O

‘UNIVERSITY OF CALIFORNIA PUBLICATIONS—(Continued)

-Vol..15. Introduction. Dependence of Marine Biology upon Hydrography and
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eos Ka 2 pea ae en Ce a HA RSIS Pe cl hoe Raat a ck Ne Re heey POE eS Ea
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UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

ZOOLOGY
Vol. 18, No. 4, pp. 61-74, plates 4-5 October 17, 1917

NEW SPECIES OF AMPHINOMIDAE FROM THE
PACING COAST

BY
CHRISTINE ESSENBERG

CONTENTS

PAGE

VEVCiS OVERDO OT, ee a ee a PE re cee 61
JETS (2 OUTTPET SES See Mee ARE Ee ne eee ee ee eer 62
CHEIEID I) GRSTCD TP GRO Sle San. Ska hi ep ees eee 62
PUES CIRO ED TE CLE LTE G(s] SCS Sh re Ne ee eee eee 63
TORONTO HANG Callyyonte), le TONS ose ece eee Saeco eco cc oee Ee eee ecm secnn 63
Huphrosyne multibranchiata, Sp. WOV. -.---.2-.---.2---------5--c--so----enee nro sense cceneensene ent 65
Tiara sgkeres SyOrU Ore Wane eh TLC L0G 5 Ree eee mae ae ee Beer or ee 66
Huphrosyne Kkyllosetosa sp. MOV. —----..--------2-<c-sceccc2-neseeesc cece ene e een eeeseeenencanneenes 68

TL opie pea EUR \CRECENG | eer ek a a en ee eee 70
TOSge SIN aor (DFE Tae iter sea sae CIES eee ee ee ee er ee 72

INTRODUCTION

The present paper is a continuation of two previous papers on
the polychaetous annelids. The study of these annelids was begun and
earried on for some time in the Zoological Laboratory of the Univer-
sity of California at Berkeley and was completed at the Scripps
Institution for Biological Research at La Jolla.

ACKNOWLEDGMENTS

The writer avails herself of the opportunity to express her hearty
thanks to Professor Charles A. Kofoid for his encouragement and for
his valuable suggestions and criticisms in this work.

The material used in this work was obtained largely from the
annelid collection of the Zoological Museum of the California Uni-
versity at Berkeley, of which a revision is being made, and from
private collections.

62 University of California Publications in Zoology [Vou. 18

GENERAL DESCRIPTION

The Amphinomidae are interesting in many ways. They have
been a problem to the various workers as to their place in the poly-
chaeta group and the question has not been definitely settled yet. Some
authors as Quatrefage (1865), have separated this family from the
Aphroditidae by the Palmiridae, Leodocidae and Lumbrinereidae.
Others, as MeIntosh (1900), disapprove of this division, claiming that
anatomical differences are not sufficient to justify it. Further dis-
agreement prevails among the various workers as to the classification
of this group. Some, as Ehlers (1864), deal with the Amphinomidae
as one family. A number of other workers treat them as two inde-
pendent families, Amphinomidae and Euphrosinidae. MeIntosh in
his first work (1885) treats the Amphinomidae as two independent
families, but in his later volume (1900) he places the subfamilies
Amphinomina and KEuphrosynina under the one family Amphino-
midae. I am inelined to follow the latter plan of classification.
Besides the various other characteristics common to both subfamilies
of the Amphinomidae, the presence of a dorsal caruncle and the loca-
tion of the mouth, which is removed ventrally from the usual posi-
tion at the tip of the snout, distinguish the Amphinomidae from all
other families of the Polychaeta.

The chief characteristics pertaining to both subfamilies are as
follows: The body is oblong or ovate-oblong. The cephalic lobe is
rounded or compressed and coalesced with the earuncle. The ecaruncle
extends over several segments. Of the two pairs of eyes both pairs
may be situated dorsally, or one pair may be situated ventrally and
the other dorsally. In the family Amphinomidae, there are two lateral
tentacles and one median. The latter, however, may be absent. The
mouth is removed from the anterior end ventrally and is surrounded
by specially modified segments. The proboscis is protrusible, devoid
of papillae and of chitinous jaws. The parapodia are biramous and
peculiarly modified. The notopodium extends on the dorsum and is
coalesced with the latter. It bears setae, branchiae and cirri, arranged
in transverse rows, frequently covering the entire dorsum of the worm,
except a narrow mid-dorsal line. The setae are usually of two or more
kinds; they are tubular, caleareous, very brittle, simple, capillary,
unequally bifurcate or serrate. The branchiae are arborescent or
pinnate; dorsal in Euphrosynina, marginal in Amphinomina. The
ventral cirri are single, the dorsal, single or double.

1917 | Essenberg: New Species of Amphinomidae 63

The members of the family Amphinomidae are confined mostly to
tropical and subtropical waters, but a few species of Eurithoé have
been reported from the lower boreal regions, and some species of
Euphrosynina have been found in the temperate zones.

The species in the collection of the Zoological Museum of the
University of California are from the waters of the coasts of Cali-
fornia, except two specimens, of which one is from the Hawaiian
waters, the other one from the sub-boreal waters. The Amphinomidae
have a varied bathymetrical distribution, ranging from the littoral
zones to depths of 2000 fathoms. They have been found on the sur-
face of the water attached to buoyant substances such as logs or
weeds. They are frequently found on kelp between tide-marks.
Some of the species live as commensals on sponges and are noted for
their remarkable adaptive coloration (McIntosh, 1900).

DESCRIPTION OF NEW SPECIES

The species of Amphinomidae of the University collection have
been enumerated by Treadwell (1914). On the following pages the
following new species are described which may be added to his list:
Euphrosyne calypta, Euphrosyne multibranchiata, Eurythoé spiro-
cirrata, and Huphrosyne kyllosetosa.

To the list of the Amphinomidae in the annelid collection of the
University of California may also be added Chloeia pinnata (Moore),
of which fourteen specimens were found in the Survey of San Fran-
cisco Bay on October 21, 1912, at Station D5788, near Farallone,
lat. 11° 30’ N., at a depth of 68 to 60 fathoms, in very fine green sand.

1. Euphrosyne calypta sp. nov.
Pl. 4, figs. 1-3, 6-7, 13-14

Diagnosis—Body elongated, rounded at both ends. Dorsum
slightly arched with segmentations definitely marked on dorsal and
ventral surfaces. Caruncle bilobed, extending to the fourth segment.
Six pairs of three- to four-lobed branchiae. Dorsal cirrus between
second and third gill-trunks.

Description.—The species is comparatively small in size. The two
specimens, type and paratype, measure 10 and 11 mm. in length,
respectively, and 6 mm. in width. The body is ovate-oblong, uniform
in width, rounded at both ends. The slightly arched dorsum is covered

64 University of California Publications in Zoology [Vou. 18

with transverse rows of branchiae and setae except a narrow mid-
dorsal bare line. The ventral surface is convex. The segmentation
is well marked by transverse folds. The corresponding numbers of
segments of the two specimens are 20 and 28. The earuncle (pl. 4,
fig. 1) is coalesced with the prostomium and is dorso-ventrally bilobed.
The posterior free end of the caruncle extends almost to the poste-
rior margin of the fourth segment. The anterior end of the caruncle
bears a tentacle consisting of a heavy basal portion and a prominent
style, about the same length. At the base of the tentacle is a pair
of large dorsal eyes. Another pair of smaller eyes is situated ventrally
between the peristomial parapodia (pl. 4, fig. 7).

The parapodia are of the usual kind. The dorsal and ventral
rami are distinetly separated. The dorsal ramus or notopodium
merges into the dorsum, extending nearly to the mid-dorsal line, cover-
ing with its numerous setae and branchiae the greater part of the
dorsum. There are three cirri, one ventral and two dorsal. The
ventral cirrus is inserted between the ventral setae, its distal end
reaching to the tips of the ventral setae. One of the two dorsal setae
occurs on the dorsum immediately posteriad of the first dorsal trunk
of branchiae. The second cirrus is situated between the second and
third gill-trunks (counting from the dorsal extremities of the series).
The dorsal cirri are stout, slightly tapering toward the distal ends.
They are of about equal length with the branchiae, and about one-
half of the length of the dorsal setae.

There are six main trunks of branchiae on each parapodium. Each
trunk is subdivided into three or four finger-like projections (pl. 4,
figs. 13-14). Anterior to each transverse row of branchiae is a row
of numerous brown, forked setae (pl. 4, fig. 2). They are bifid, long,
tubular, and hollow, with the distal end of the longer projection
slightly tapered and the tip slightly curved. One type of dorsal setae
only is present, although the setae vary in size. The ventral setae are
similar in shape to the dorsal. They are long, one-half the width of
the body, hollow, brittle, with the tips obtusely rounded (pl. 4, fig. 3).
The setae and the branchiae incline anteriorly near the anterior por-
tion of the body (pl. 4, fig. 1), and posteriorly on the posterior portion
of the body.

The buceal region extends to the fifth segment (pl. 4, fig. 7). The
eaudal cirri (pl. 4, fig. 6) are fleshy and obtusely rounded.

Comparison.—This species has been previously classified by Tread-
well as Ewphrosyne aurantiaca Johnson. It resembles the latter at

1917] Essenberg: New Species of Amphinomidae 65

first sight in the general appearance, but differs from it in some essen-
tial characteristics. The setae in the two species differ in color and
in structure. The setae are brown and only of one kind in Euphro-
syne calypta; they are white in Huphrosyne aurantiaca, and the
dorsal setae are of two distinct kinds. Further differences are in
the location of the cirri. In EF. calypta the mid-dorsal cirrus is between
the second and third gill-trunks; in H. aurantiaca the cirrus is
between the third and the fourth gill-trunks, counting from the dorsal
line. £. calypta has six pairs of three- to four-lobed branchiae on
each segment; H. aurantiaca has seven pairs of seven-lobed branchiae
on each segment.

Occurrence.—The type is a dark gray color in aleohol. It has been
found in the channel off Santa Barbara. Further data lacking. The
other specimen is tan-brown in color. Its locality is unknown.

2. Euphrosyne multibranchiata sp. nov.
Pl. 4, figs. 4-5, 8-12

Diagnosis—Comparatively large-sized worm. Body elongated
obtusely rounded at both ends. Dorsal and ventral surfaces convex ;
setae long and brittle; carunele bilobed and long, extending to the
seventh segment.

Description —tThe classification of this species is based on a single
specimen. It is a large worm, for this genus. The length of the body
is 40 mm., the width in the widest part of the body (between segments
26 and 29) 13 mm., exclusive of the setae. From these segments the
width of the body decreases towards both ends. The body is elongated,
slightly wider in the center, very gradually decreasing in width
toward the ends, which are obtusely rounded. The dorsal and the
ventral surfaces are convex and the segmentation is well indicated
on both sides by transverse ridges. The number of the segments in
this specimen is 45. Except for the narrow mid-dorsal bare line, the
dorsum is covered with rows of branchiae and setae. The color of
the worm is grayish-brown with ventral setae light yellow, almost
white.

The prostomium is deeply sunken between the peristomial para-

podia and fused with the dorsally located bilobed caruncle. The
' earunele (pl. 4, fig. 11) is long with its free end extending to the
seventh segment. It is bilobed dorso-ventrally. The dorsal lobe is
grooved and evidently longer than the ventral, for it is coiled in a

66 University of California Publications in Zoology _[Vou. 18

zig-zag line. The median tentacle consists of a long, heavy basal por-
tion and a short style about one-fourth the length of the former. At
the base of the tentacle on each side of it are a pair of eyes partly
covered by the tentacle when the latter is bent posteriorly. The ven-
tral eyes (pl. 4, fig. 12) are small, flanked on each side by very small
antennae. The palpi are broad and flat, divided longitudinally by
a median cleft. The mouth (pl. 4, fig. 12) is bordered posteriorly by
the fifth segment.

The parapodia are typical of the genus, with the notopodium
merging into the dorsum. The setae are of two kinds. The ventral
setae (pl. 4, fig. 4) are long, one-third of the width of the body,
slender, hollow, and very brittle, of straw color with a subterminal
spur. The dorsal setae are similar in shape (pl. 4, fig. 5) but they are
much shorter and stouter than the ventral, slightly surpassing the
length of the branchiae (pl. 4, fig. 10).

There are ten to eleven pairs of branchiae on each segment. The
main trunks of branchiae (pl. 4, figs. 8, 9, 10) are subdivided into
smaller finger-like projections, the number of which may vary accord-
ing to the size of the trunk. The finger-like ramifications are usually
about 10 to 12 on a trunk, but some of the gill-trunks of the anterior
end have only about 5 or 6 ramifications.

There are two dorsal cirri and one ventral. The short and heavy
ventral cirrus (pl. 4, fig. 12) is situated at the posterior edge of the
neuropodium on the ventral surface. The two dorsal cirri are short,
stout, attenuating toward the end, terminating bluntly (pl. 4, fig. 10).
The dorsal cirrus is posteriad of the last dorsal gill-trunk. The lateral
cirrus is between the fifth and the sixth gill-trunks, counting from
the mid-dorsal line. It is short, reaching only halfway the length of
the branchiae.

The single specimen in the collection is from Kodiak Island,
Alaska. Further data unknown.

3. Eurythoé spirocirrata sp. nov.
Pl. 4, figs. 15-17; pl. 5, figs. 18-23
Diagnosis.—Body long, slender, gray in alcohol. Dorsal surface
shghtly convex. Ventral surface strongly convex. Sides between
parapodia vertical and flat. Branchiae marginal. Two cirri on each
parapodium. Caruncle broad, smooth, extending to fourth segment.
Description.—The species is a typical representative of the genus
Eurythoé. The body is long, somewhat uniform in width, very grad-

1917] Essenberg: New Species of Amphinomidae 67

ually attenuating toward the posterior end and with -both ends
obtusely rounded. The dorsal surface is almost straight and only
slightly arched. The ventral surface is strongly convex. The length
of the body is 55 mm., the width, in the widest part of the body (about
segments 29 and 30), 13 mm. The segmentation is well shown on the
dorsal and the ventral surfaces, as well as on the vertical sides. The
number of segments is 66. The caruncle (pl. 5, fig. 18) is coalesced
with the prostomium. It is broad and smooth without any grooves
and extends to the fourth segment. It has one short median tentacle.
The posterior end of the caruncle is narrow and cleft. The prosto-
mium bears two pairs of cirri. No eyes are visible on this specimen.
The buceal region extends to the fifth segment (pl. 5, fig. 19). The
cirri are spirally constricted. The parapodia (pl. 4, fig. 17) are made
up of two widely separated rami. The ventral ramus bears a spirally
constricted cirrus and a fascicle of comparatively short setae about
one-half the length of the cirri (pls. 4 and 5, figs. 17,19). The ventral
setae (pl. 5, figs. 22, 23) are light yellow, hollow, brittle, with a sub-
terminal prong, ending bluntly. The dorsal division bears a ramose
gill (pl. 4, figs. 15, 16,17). The gill-branches increase in complexity
toward the median and posterior portions of the body. The dorsal
setae are of two types. One type (pl. 5, fig. 20) is strongly serrated,
ending bluntly; the other, very fine, straight, the distal end slender
and pointed, with very minute serrations above the prong (pl. 5,
fig. 21).

Comparisons—The worm was labelled as EHurythoé califormea.
It differs from EF. californica Johnson by the shape of the caruncle,
which is narrow and twisted in the latter species, with the prostomium |
bounded anteriorly by a peculiar crescent-shaped margin. In Eury-
thoé spirocirrata the caruncle is smooth and broad. Further differ-
ences are evident in the setae, which are entirely different in the two
species. The ventral setae differ in shape, and the two kinds of
serrated dorsal setae present in E. spirocirrata are represented in
E. californica by perfectly smooth, straight setae without any serra-
tions. The cirri are spirally twisted in Eurythoé spirocirrata; they are
straight in Z. californica. Comparing the illustrations as well as the
specimens of both species, one can see at once the characteristic dif-
ferences.

Eurythoé spirocirrata resembles E. pacifica Kinberg more in gen-
eral appearance and in the shape of the body. It differs from the
latter in the broad shape of the caruncle, by the spirally twisted cirri,

68 University of California Publications in Zoology Vou. 18

by the absence of eye-spots and by the shape of the setae. In ELury-
thoé pacifica the ventral setae are more strongly bifurcated with a
few serrations on the coneave side of the longer fork.

The habitat of the worm is unknown. Most probably it comes
from the vicinity of San Diego.

4. Euphrosyne kyllosetosa sp. nov.
Pl. 5, figs. 24-31

Diagnosis —Body ovate-oblong. Dorsum arched and covered with
branchiae and setae. Naked mid-dorsal line about one-fifth of the
width of the body. Carunele bilobed, long, extending to the fifth
segment. Branchiae 6 to 7 pairs on each segment. Dorsal setae of
two kinds, unevenly bifureate smooth; and strongly bifurcate serrate.

Description —It is a comparatively small worm measuring 1] mm.
in length and 6 mm. in width including setae. The respective num-
ber of segments in the two specimens, type and cotype, are 31 and 32.
The dorsum is convex, densely covered with branchiae and setae,
except a narrow mid-dorsal line about one-fifth of the width of the
body which is bare. The prostomium is coalesced with the peris-
tomium and is partly concealed by the long bilobed caruncle dorsally.
The crest of the earuncle (pl. 5, fig. 24) is marked by longitudinal
grooves. The median tentacle consists of a long basal portion and a
style of equal length. The whole tentacle is about one-half of the
length of the caruncle. At the base of the tentacle is a pair of eyes.
The caruncle is comparatively long, with its free end extending to the
fifth segment. The palpi are broad, flattened pads (pl. 5, fig. 25).
continuous by their anterior ends with the peristomial parapodia.
The mouth is bounded anteriorly by the palps, and posteriorly by
a V-shaped furrowed lip. The buceal region extends to the fourth
segment. The ventral eyes (pl. 5, fig. 25) are small. The biramous
parapodia are of the kind characteristic to the genus. The notopodia
are sessile, merging into the dorsum; the neuropodia lateral, slightly
projecting lamellae. The cirri are about equal to the gills in length,
stout, slightly tapered. The notocirrus is situated mediad of the
setae palisade and a little anterior to the branchiae. The lateral or
middle cirrus is in line with the notocirrus and is between third and
fourth gill-trunks, on the anterior segments, between the second and
third gill-trunks (counting from the dorsum). The neurocirrus is
similar in shape, situated within the postero-ventral margin of the
neuropodial fascicle of the setae.

1917 | Essenberg: New Species of Amphinomidae 69

Branehiae occur on all setigerous segments, usually six pairs on
a segment, but there may be only five pairs on the few extreme ante-
rior segments, and seven pairs on the median segments. LHach gill-
trunk consists of a stem dividing dichotomously several times. The
gills vary in size, the individual projections ranking from four to
eight in number on each gill-trunk (pl. 5, figs. 31, 32).

The notopodial setae (pl. 5, figs. 26, 28, 29) are arranged in a long
palisade of two rows along the entire length of the gill-series. They
all are hollow, calcareous, translucent and yellowish-white. They
are comparatively short, some projecting slightly beyond tips of the
gills. The serrated bifid dorsal setae (pl. 5, figs. 28, 29) are narrow,
enlarging near the place of foreation. Both forks are slightly bent,
strongly serrated along the inner borders, and are covered with fine
asperities. The serrated dorsal setae are more numerous on the ante-
rior portion than on the rest of the body. The dorsal setae of the
second row (pl. 5, fig. 26) are of the simple form, incompletely bifid,
one of the forks being much longer, about three times the length of
the shorter fork, with almost straight, smooth tips. The neuropodial
setae (pl. 5, figs. 27, 30) arise in several rows from an elliptical area.
They are similar to the smooth dorsal setae but are much stouter and
longer than the latter. The length of the ventral setae varies, those
in the dorsal part of the fascicle being the longest (about 1 mm.),
the setae decreasing in length as they proceed ventrad.

Comparison.—The species resembles somewhat EFuphrosyne dumosa
Moore (1911), but differs from it in the lesser number of gill-trunks
and in the shape of the setae. Huphrosyne dumosa has 10-11 pairs
of branchiae on each segment; E. kyllosetosa, 6-7 pairs. The setae
differ considerably in the two species. The distal ends of the noto-
setae as well as of the neurosetae are more slender in EL. dumosa than
they are in FE. kyllosetosa, and the shorter fork of the non-serrated
setae is very short, almost rudimentary, in HE. dumosa. Other minor
differences may be found in the shape of the branchiae and in other
characteristics.

The two specimens, type and cotype, were collected between tide-
marks from drifting kelp near La Jolla, California, and were kindly
presented to me by the collector, Mr. H. O. Falk. They are now in
the annelid collection of the University of California in Berkeley.
Five specimens of EF. imbata Moore have been given to me by the
same collector and are now in the annelid collection of the Zoological
Museum of the University of California at Berkeley. They were
collected on December 4, 1915, from kelp holdfasts off La Jolla.

70 University of California Publications in Zoology [Vou.18

LITERATURE CITED

EHLERS, E.
1864-1869. Die Borstenwiirmer. Annelida Chaetopoda nach systematischen
und anatomischen Untersuchungen dargestellt (Leipzig, Englemann),
1-748, pls. 1-24.
1887. Reports on the results of dredging in the U. S. Coast Survey Steamer
‘<Blake.’? Mem. Mus. Comp. Zool. Harvard, 15, 1-335, pls. 1-60.

JOHNSON, H. P.
1897. <A preliminary account of the marine annelids of the Pacific Coast
with descriptions of new species. Proc. Calif. Acad. Sci., (3) 1,
153-193, 5 pls.
1901. The Polychaeta of the Puget Sound Region. Proc. Bost. Soc. Nat.
Hist., 29, 381-437, 19 pls.
KINBERG, J. G. H.
1857. Nya slagten och arter af annelider. Ofv. K. Sv. Vet. Akad. Forh.,
14, 11-14.
McIntosH, W. C.
1885. Reports on the scientific results of the voyage of H. M.S. ‘‘Challenger’’
Expedition. 12, 1-554, pls. 1-55, 1A-39A, 1 map.
1900. Monograph of the British annelids. Part II, Polychaeta, Amphino-
midae to Sigalionidae (London, Ray Society), 216-442, pls. 24-
26, 26A, 27-42.
Moore, J. P.
1911. The polychaetous annelids dredged by the U. S. S. ‘‘Albatross’’
off the coast of Southern California in 1904. Proc. Acad. Nat. Sci.
Phila., 68, 234-318, pls. 15-21.
TREADWELL, A. L.
1914. Polychaetous annelids of the Pacific Coast in the collections of the
Zoological Museum of the University of California. Univ. Calif.
Publ. Zool., 13, 175-238, pls. 11-12, 7 figs. in text.

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EXPLANATION OF PLATES
(All figures drawn with camera lucida)

PLATE 4

Fig. 1. Dorsal view of anterior portion of Euphrosyne calypta. X 10.

Fig. 2. Tip of dorsal seta of EHuphrosyne calypta. X 160.

Fig. 3. Tip of ventral seta of the same. X 160.

Fig. 4. Tip of ventral seta of Huphrosyne multibranchiata. X 160.

Fig. 5. Tip of dorsal seta of Euphrosyne multibranchiata. X 160.

Fig. 6. Posterior segments of Huphrosyne calypta, showing caudal cirri. X 10.
Fig. 7. Ventral view of anterior end of Euphrosyne calypta.

Fig. 8. Branechiae of Euphrosyne multibranchiata. X 20.

Fig. 9. A branch of the gills of Huphrosyne multibranchiata. X 20.

Fig.10. Three gill-branches of Huphrosyne multibranchiata, showing the
dorsal cirrus and the setae in their relative positions. X 20.

Fig.11. Caruncle of EZuphrosyne multibranchiata. X 10.

Fig. 12. Ventral view of anterior end of EHuphrosyne multibranchiata. X 10.
Figs. 13-14. Branchiae of Euphrosyne calypta. X 79.

Fig. 15. Branchiae of Lurythoé spirocirrata. X 10.

Fig. 16. A branchlet of the preceding. X 20.

Fig.17. Twentieth parapodium of Hurythoé spirocirrata. X 20.

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PLATE 5

Dorsal view of anterior portion of Eurythoé spirocirrata, showing
relative position of caruncle. X 10.

Anterior ventral view of Hurythoé spirocirrata. X 10.

Tip of stout, serrated dorsal seta of Hurythoé spirocirrata. X 160.

Tip of fine dorsal seta of Hurythoé spirocirrata. X 160.

Tip of smaller ventral seta of Hurythoé spirocirrata.
Tip of stouter ventral seta of Hurythoé spirocirrata.
Caruncle of Huphrosyne kyllosetosa. X 20.

Ventral view of anterior end of same. X 10.

Tip of dorsal seta of Huphrosyne kyllosetosa. X 320.

Tip of ventral seta of Huphrosyne kyllosetosa. X 320.

Tip of serrated dorsal seta of same. X 320.
Same.

Tip of ventral seta of Euphrosyne kyllosetosa. X 320.

Branchiae of the same. X 40.
Branchlets of the same. X 40.

[74]

x 160.
x 160.

UNIV: CALIF. PUBL. ZOOL. VOL, [8 [ESSENBERG] PLATE 5

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UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN
ZOOLOGY
Vol. 18, No. 5, pp. 75-88, 35 text figures December 29, 1917

CRITHIDIA EURYOPHTHALMI, SP. NOV.,
FROM THE HEMIPTERAN BUG,
EURYOPHTHALMUS CONVIVUS STAL

BY
IRENE McCULLOCH

CONTENTS

PAGE
Herat feTyO CIIUG tal OT pete eee ee aces Seen nS AS Soca ds, Sa th oe cae ea RL ee eee 75
Comparison of Crithidia leptocoridis and C. euryophthalma .......-.-..-------------------- 76
Morphology of the digestive tract of Euryophthalmus convivus ..........--..---------- 78

Infection of the digestive tract of Huryophthalmus convivus by Crithidia
CO NO DN OH 2 DAN Os Pen ae Be A aE ee Ree eee eee oe 81
ihe syle tO tan C7uUh CmCUNY OPPTULILOL TVD oon ee cn acco nance nsec eee caesarean cence ence 82
HEY OTNS eh OV DOM CTO [te eteenee at ees teers ES As ee. eer 83
(ORM ASTOR RE TE TN ek ne eee as ee te 83
Developunomenibhidialle Stale es esc se cet noes eee ce eet seen ene ee eee oe 83
DMRUU REE HRS) TEATS eee eee a ee ee Oey ee eee 83
SOMITE leper cet eae eee Sacre oooh Bn nsec ne A ee ee re 83
Itayiereineill @re rnGlopaxernOvorSs LOO KC MDA ee oer cere eecc senor eee semen serp ace eensreee een EoE 84
TEMAS: TENSISSMOSOT) See ae ge Rn ne ae Be en a ee ae 84
TEGTAGTUSS TELCO NAAN! "Te] OVE ao LHe UA 0 eee ec Se A ae eee 85
HonmMs se LrOMleu Me MWY LOLIC CXPAN SION seco cans sec cet sap ae sas acee cence. sh aesae researc ecneae 85
INEC LOT OTT AS eee ence te See aE to cee c asec ee ee i goes es can ceeta Wasuue seach sunaet ance catee 86
NEV UT UO E11 ONUACLS tase teh coc cone sess cee nde ste ence Raven Seen spear ec ere aetna eee es ecee at ee 86
EGXCHTCIL ” SECTS TONS Se ae ea a OE Pe ee ee 86
MMPECCiIVve sane GesenercilVve (CYCLES <<! o 82s Si dac-nactoapeeoae sae become resect atm ene cccomrccn 87
AS HEICAE STENT a Se a ae ees 87
HTB ONG URC Ct C Olumeereea Be Sess ccte tee a sac Sea ccsa sa deceent a scasacccct de wbaceee saemert cee anfun estan so wusenen 88

INTRODUCTION

During the late summer and early fall, large numbers of Hury-
ophthalmus convivus can be found ‘feeding upon Lupinus arboreus
Sims, one of the common lupines growing on the sand dunes of San
Francisco near Golden Gate Park. Many bugs can also be detected

76 University of California Publications in Zoology [Vou.18

readily in the grass, dead leaves and sand beneath the bushes. The
adults are protected in part by their coloration which is a dusky black
with dull yellow wing-markings. The young, on the contrary, are
conspicuous objects because of their shiny, steel-blue color. The
tendency, also, of the nymphs to remain for some time in a compact
mass increases the conspicuousness of their coloration.

An examination of the contents of the digestive tract of these
insects revealed in eighty per cent a heavy infection of flagellates in
certain portions of the mid gut, namely: the crop, the mid-stomach,
and the pyloric expansion (fig. 1, cr., mid., stom., pyl. ex.). Close
observation of these parasites at once placed them in the genus
OCrithidia. At first it was thought that they belonged to the species
of Crithidia previously deseribed by me (1915) as Crithidia lepto-
coridis. However, further investigation of the morphology and life
cycle of both flagellates has presented sufficient evidences to justify
the placing of the two flagellates in distinct species. Accordingly, the
flagellate parasitic in the digestive tract of Luryophthalmus convivus
has been called Crithidia ewryophthalmi, sp. nov.

COMPARISON OF CRITHIDIA LEPTOCORIDIS AND C. EURYOPTHALMI

A tabular comparison of these two species of Crithidia leptocoridis
and C. euryopthalmi, from the plant-feeding bugs, Leptocoris trivit-
tatus and Euryopthalmus convivus, respectively, will now be given.

C. leptocoridis C. euryopthalmi
Size
Length 20u to 40z. Length 10, to 30u.
Width 1.54 to 3u. Width 1.74 to 2.5y.

(A) Location of parasites
(1) Stomach

(a) Crop

Abundant infection present at Abundant infection containing
certain periods. Few spore forms many spore forms at certain per-
have been found. iods. Wide range of forms in-

eluding, possibly, two types of
multiple fission.

(b) Mid-stomach
No division comparable to this Usually infected with spore and
in Leptocoris. flagellated stages of the parasites.

(c) Pylorie expansion
No division comparable to this Exceedingly heavy infection
in Leptocoris. nearly always present in adults.
Stages here are comparable to
those of the rectum of Leptocoris.

1917] McCulloch: Crithidia euryophthalmi TA

(2) Intestine
Infection here somewhat com-
parable to that of the mid-stomach
of Euryophthalmus convivus. Spore
forms are seldom found here.

(3) Rectum
Heavy infection usually present
in adults. Spore forms not com-
mon. The stages found here are
comparable to those of the pyloric
expansion of Luryophthalmus.

(B) Myonemes
Usually present in a definite
number and position on the body.

(C) Parabasal body
Noticeably bilobed along an-
terior edge in nearly all of the
erithidial stages.

(D) Parabasal rhizoplast
Fan-shaped mass made up of
numerous, colorless, thread-like

fibers.

(E£) Blepharoplast
Some forms show an enlarge-
ment at the base of the flagellum.
This stains lightly and can not be
defined as a definite basal granule
or blepharoplast.

(F) Nucleus -

The nucleus not commonly found
with a chromatin encrusted mem-
brane and a central karyosome.
The chromatin is frequently broken
up into several granules.

(G) Degeneration
Shown by numerous chromidia
in cytoplasm, broken up chromatin
granules and vacuolated cytoplasm.

(H) Spore forms
Few preparations show spore
forms.

No infection has been found in
the intestine.

Spores only have been found in
the normal preparations of the ree-
tum. Two preparations only from
fifty insects showed infection.

Not readily found and probably
occur in no definite position on the
body.

Seldom shows any indication of
the bilobed appearance.

Outline of fan-shaped parabasal
rhizoplast clearly defined but no
internal structure has been dis-
cerned.

Little evidence to show that
there is normally any enlargement
which could be regarded as
blepharoplast from a purely struc-
tural standpoint.

Nucleus as a rule shows a echro-
matin enerusted membrane with a
central karyosome.

Shown chiefly by vacuolated
cytoplasm. Entire nucleus may
be diffused, but the chromatin is
most frequently in the form of
a central granule. Chromidia are
not numerous.

Almost all of the preparations
show a few or many spore forms.

78 University of California Publications in Zoology [Vou.18
(1) Binary fission
More abundant in the crop and
rectum.

Found in the crop and pylorie
expansion, but it has not yet been
found in the rectum.

(J) Multiple fission
(1) Somatellae
Somatellae have not been found A few cases have shown soma-
showing flagellated zooids. tellae in the crop. These are
: spherical in shape containing a
variable number of flagellated
zooids.
(2) Internal budding

Process comparable to that of A variable number of non-flagel-

C. euryophthalmi results in a for-
mation of numerous small’ non-
flagellated zooids within the body
of the parent.

lated zooids are formed within the
body of the flagellates in the crop.
The parent body degenerates set-
ting free the numerous small spore-

like forms or zooids.

From the above tabular comparison, it will be noticed that in
general the differences between the two species are of two types,
morphological differences of minor importanee, and developmental
differences, seemingly of great importance, especially from the stand-
point of transmission of the flagellate. Certain small, non-flagellated
forms (figs. 11, 19, 27, 35) are constantly present in the life cycle
of C. euryophthalmt. However, further investigation of the mor-
phology and life cycle of both flagellates may prove the separation
of these two species to be untenable. It is possible that more knowl-
edge of the structural modifications of these parasites due to food and
digestive juices of the host will account for all the differences above
tabulated. It must also be taken into consideration that these flagel-
lates are microscopic forms with few characters and that the differ-
ences existing between the two species of this group will be necessarily
shght as compared with differences between two species of Metazoa.

I am indebted to E. P. Van Duzee of the California Academy of
Sciences for the identification of this insect; and to Dr. C. A. Kofoid

for suggestions and eriticism of this work.

MorPHOLOGY OF THE Digestive TRACT OF EURYOPHTHALMUS CONVIVUS

The alimentary tract of the bug, Huryophthalmus convivus has
three divisions, the fore-, mid-, and hind-gut.

The Fore-gut.—The fore-gut as indicated in the diagram (fig. 1,
oes., prov.) shows the two parts, the oesophagus and proventriculus.
The foregut consists of the mouth, pharynx, and oesophagus (fig. 1,
oes.). The oesophagus is a short, delicate tube of thin, white, almost

transparent tissue. Following the oesophagus is the anterior end of

1917 | McCulloch: Crithidia euryophthalmur w

the crop into which projects the cardiae valve. This portion of the
crop is of smaller calibre than that posterior to it and usually appears
to be invaginated into the main cavity of the crop.

The Mid-gut.—The mid-gut of Euryophthalmus convivus is rela-
tively much more complex than that of Leptocoris trivittatus or of
the Heteroptera in general. One of the early investigators (Dufour,
1833, pl. 2, fig. 13) figures in Coreus marginatus a digestive tract
with similar parts but the nomenclature for these parts has not been
definitely established. The digestive tract of Lygaeus militaris (Pat-
ton, 1908) is somewhat lke that of Euryophthalmus convivus. His
use of the term mid-intestine is questionable ; hence we have preferred
to use the word intestine (fig. 1, int.), believing that the anterior three
parts of the mid-gut are all parts of the stomach proper. Accordingly
these three parts have been designated respectively, as the crop, the
mid-stomach and the pyloric expansion.

The crop is the first division of the mid-gut and is characteristically
of a light yellow color. This portion of the gut presents an ellipsoidal
shape, more or less irregularly lobed, and capable of great dilation.
During the fasting period this region is filled with gas.

Immediately posterior to the crop is another enlargement of the
mid-gut which we have designated as the mid-stomach (fig. 1, mid-
stom.). This enlargement oceurs regularly, and is of a yellowish
brown color which is due almost entirely to the contents. The size
of this portion varies from one-half to one-third of that of the crop.
The mid-stomach and the next enlargement, the pyloric expansion,
may contain equal amounts of the contents, or either one may be
ereatly distended at the expense of the other, depending upon the
stage of digestion.

A narrow tube connects the mid-stomach with the pyloric (fig. 1,
pyl. ex.). This pylorie division is a symmetrical bulb-like enlarge-
ment filled with a dark brown liquid giving to this part of the tract
a blackish appearance.

The last division of the mid-gut is a unique structure which we
have ealled the intestine (fig. 1, int.) with a continuously attached
intestinal gland (fig. 1, int. gl.). The canal or intestine passes through
the center of the ruffle-like band of white, almost transparent, gland-
ular tissue (fig. 1, int. gl.). The intestine and gland of the intestine
are approximately equal in length to the anterior three portions of
the mid-gut just described. A similar structure was described by
Dufour (1833, pl. 2, fig. 13) in the hemipteran bug, Coreus mar-
ginatus.

80 University of Califorma Publications in Zoology [Vou.18

. mid. stom.

|
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!
'
'
!
'
'
!
:
-

a
ye
=
m
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14 15 16

19 @, 6, @, 0, 8, @

Fig. 1. Diagram of the digestive tract of Ewryophthalmus convivus, including
the portion between the oesophagus and anal opening. Accompanying this dia-
gram is a series of outline drawings (figs. 2-35) of the characteristic forms of the
flagellate, C. euwryophthalmi, found in the several positions of the digestive tract.
Oes., oesophagus; cr., crop; mid. stom., mid-stomach; pyl. exp., pyloric expansion ;
int., intestine; int. gl., gland of intestine; m. t., malpighian tubules; c., colon;
ie eeCuuMen ex Lio Oe

Figs. 2-3. Forms from the crop. Fig. 2. The initial infective spore.

Figs. 3-6. Developing crithidias.

Fig. 7. Binary fission in non-flagellated forms.

Figs. 8-9. Multiple fission in form of a somatella containing zooids.

1917 | McCulloch: Crithidia euryophthalmi 81

Fig. 10. Elongate flagellate showing structures common to these forms: fl.,
flagellum; und. m., undulating membrane; Db/., blepharoplast; par. rh., parabasal
rhizoplast; par. b., parabasal body; rh., rhizoplast; n., nucleus.

Fig. 11. <A disearded flagellum and parabasal body with one of the zooids
showing the results of the internal budding process of figure 12.

Fig. 12. Modified form of multiple fission designated as internal budding,
flagellum and parabasal body present, zooids in the parent body.

Figs. 13-19. From near the entrance of the pyloric expansion. Fig. 13. An
attached or haptomonad form found on wall near entrance to the pyloric expan-
sion. Figs. 14-15. Nectomonad or free forms. Figs. 16-18. Haptomonad forms.
Fig. 19. Oval spore form.

Figs. 20-27. Forms from the pyloric expansion. Figs. 20-22. Haptomonads
or attached forms. Figs. 23-26. Nectomonads or free forms. Fig. 24. Binary
fission form. Fig. 27. Oval spore form.

Figs. 28-35. Oval spore forms from the rectum. Probably the infective forms
of C. euryophthalmi.

The Hind-gut.—The hind-gut is composed of two parts, the eolon
and the rectum. The colon is a thin, transparent, three-lobed structure
(fig. 1, c). Into each of the two lateral lobes opens one of the mal-
pighian tubules (fig. 1, m. ¢.), while the apex of the middle lobe is
joined to the intestine.

The rectum is an almost transparent, ovoidal structure with the
larger end toward the colon. It gradually tapers down to a narrow
tube leading to the anal opening. The rectum is found either col-
lapsed, or greatly distended with a clear brown liquid.

INFECTION OF THE DIGESTIVE TRACT OF EURYOPHTHALMUS CONVIVUS
BY C. EURYOPHTHALMI

Three parts of the digestive tract, the fore-, mid-, and hind-gut,
were carefully examined, each part separately, for flagellates. The
examination of the several parts of the fore-gut, namely: the
oesophagus and proventriculus, has always yielded negative results.
The hind-gut has shown a slight infection in the rectal portions in
a few instances, but the mid-gut has in almost every case shown a
heavy infection of C. euryophthalmi in one or more of its several
parts. This heavy infection may be either in the crop, the mid-
stomach, or in the pyloric expansion. Few adults are free from
ereat masses of attached parasites completely covering the inner
surface of the pyloric expansion. When this condition exists there
is little evidence of an epithelial lining to be found in this division
of the mid-gut.

The study of the stages of the life cycle of the flagellate shows
that those stages normally found in the rectal portion of other Hemip-

82 University of California Publications in Zoology [Vou.18

tera are here found in the pyloric expansion of the mid-gut. This
may be due in part to the presence of the intestinal gland and in
part to certain chemical or physiological conditions within the several
parts of the digestive tract. The investigation thus far indicates
that probably only resistant spore forms succeed in reaching the
rectum through the intestine. However by means of pressure upon
the abdomen some of the contents of the pyloric expansion can be
forced through the intestine and ejected through the anal opening
along with the rectal contents. These contents from the pyloric
expansion are usually swarming with free, flagellated parasites.

Lire Cyc Le oF C. EURYOPHTHALMI

In the life cycle of C. euryophthalmi in Euryophthalmus convivus
there are present the following types in the stomach proper which is
made up of three parts, the erop, the mid-stomach and the pyloric
expansion. It must also be emphasized that the whole life cycle
of this flagellate occurs in the several parts of the stomach.

(1) Oval spore forms (fig. 2) in the initial infective stages in
the crop.

(2) Developing erithidial stages from the non-flagellates (fig. 2,
4-5) present in the crop, which migrate posteriorly into the mid-
stomach and pyloric expansion.

(3) Multiple fission forms, probably of two types (a) a somatella
(figs. 8, 9); (b) a modified type designated as internal budding (fig.
12). These have been found only in the crop.

(4) Binary fission forms in the crop (fig. 7), and in the pyloric
expansion (fig. 24).

(5) Crithidial stages from the crop, which become free forms in
the mid-stomach and pyloric expansion, called nectomonads (Minchin
and Thomson’s terminology, 1915).

(6) Crithidial stages from the crop, which become attached forms
in the mid-stomach (fig. 13) and pyloric expansion (figs. 21-23),
termed haptomonads.

(7) Final spore stages are found in both the mid-stomach and
the pyloric expansion. Some of these succeed in reaching the rectum
through the intestine. The staining capacity of these indicate that
they probably become more resistant to destructive agencies by form-
ing a protective covering.

1917] McCulloch: Crithidia euryophthalmui 83

FORMS FROM THE CROP

Oval Spore Forms.—In the crop of approximately twenty per
cent of the nymphs and two per cent of the adults oval spore forms
together with the developing forms can be found. The oval spore
forms have been regarded as the infective spore taken up casually
with the food by the host. They are 3.2» long and 7.4» wide (fig. 2).
The anterior end is slightly pointed while the posterior is blunt. They
have a very characteristic shape and retain the haematoxylin stain
for a longer period than the other forms of the flagellate. Internally
the nucleus and parabasal body are relatively large. These two
deeply staining structures are connected by the nuclear rhizoplast
which retains enough of the stain to make it readily visible under
a high-power binocular microscope. The oval spore forms with their
characteristic staining capacity, size, and nuclear structure can be
pointed out among the parasites of the mid-stomach (fis. 1, 19) and
of the pyloric expansion (fig. 27). The development of these oval
spore forms into flagellates has been followed in part in the living
material. The several stages in development have not been followed
for the same individual, the process having been studied in a dis-
connected manner.

Developing Crithidial Stages——The oval spore form begins to
unfold slightly at the anterior end. The flagellum is bent back along
the body as far as the parabasal body. This straightens out anteriorly
and accompanying this change there is an elongation of the posterior
end (fig. 3). The whole series of developing forms gradating from
the non-fiagellated forms (fig. 2) to the large elongated flagellates
ean be found readily in almost all preparations of the infected crops.

MuutTIeteE FissionN—SoOMATELLA

In four instances out of two hundred crops examined, spherical
forms were found showing a variable number of nuclei and parabasal
bodies together with a multiplication of the number of flagella. The
flagella may project from spherical surface in various directions.
The origin of the several nuclei and parabasal bodies within this
plasmodial mas has not been followed in detail; at the present time
these spherical forms are regarded as somatellae which are common
to many of the flagellates. There is little evidence to show that this
process of multiple fission is of any importance in the multiplicative
phase of the parasite, since it occurs so rarely. Its relation to a

84 University of California Publications in Zoology [Vou.18

possible sexual phase as yet undetermined may be suggested, but no
proof is as yet available of the validity of this hypothesis.

Internal or Endogenous Budding.—Under multiple fission also
the process which we have designated as internal budding has been
included since it is regarded as a modified form of multiple fission
(fig. 12). In this large flagellated form a number of small zooids
ean be counted. It was of the greatest interest to find that such a
flagellate containing numerous zooids still retained intact its para-
basal body. Neither the original parabasal nor the flagellum enters
into the formation of the zooids. On the contrary, preparations are
in hand showing fields wherein numerous discarded flagella usually
bearing the parabasal body still attached can be found. Along with
these detached flagella (figs. 1, 10) are myriads of small zooids result-
ing from the process of internal budding. The zooids are not all of
the same size. Many minute forms are found containing the two
deep-staining structures, the nucleus and the parabasal body.
Between these minute forms and the oval spore forms previously
described is a complete series of forms varying slightly in size. The
eytoplasm of the small forms called zooids differs from that of the
oval spore forms in its staining capacity. The zooids do not retain
the haematoxylin as long as the oval spore forms. This is true of
the zooids and oval spore forms in the crop, mid-stomach, and the
pylorie expansion.

Previous to the discovery of sufficient stages in this internal bud-
ding process to determine its nature, the appearance of so many
zooids was most puzzling. Preparation after preparation was exam-
ined showing the field literally covered with the minute forms with
no clue as to their origin. This is explained by the fact that out of
two hundred preparations of the crop only three show the early or
beginning stages of the process of internal budding. A knowledge
of the feeding habit of the bug and of the time necessary for the
ingested spores to develop into mature flagellates would undoubtedly
greatly facilitate the investigation of this process. A more detailed
discussion of internal budding together with the figures showing the
process in all the stages will appear in a later paper.

Binary Fission.—Binary fission occurs among the zooids (fig. 7)
in the crop and among the flagellated forms in both the crop and
pyloric expansion (fig. 24). It probably occurs in the mid-stomach
but no record has been made of its occurrence there. If the number
of forms in binary fission found in the living material or stained

1917] McCulloch: Crithidia euryophthalmi 85

preparations can be used as a definite evidence, this process does not
play an important part in increasing the numbers of flagellates. The
small number of preparations of the crops which show an infection
leads to the conclusion that the developing flagellated forms and zooids
pass back into the mid-stomach and into the pyloric expansion after
a very short period of development in the crop.

FORMS FROM THE Mip-SToMACH

The series of forms found in the mid-stomach are shown in figures
13-19. These may be divided into three classes: (1) the small oval
spore forms (fig. 19) and small zooids, (2) nectomonad or free flagel-
lated forms (figs. 1, 4-18), and (3) haptomonads or attached forms
(fig. 13). Owing to the relatively small percentage of infection of
the preparations in the mid-stomach as*compared. with that of the
preparations from the pyloric expansion, there is probably a migra-
tion of the parasites from this portion of the mid-gut into the pylorie
expansion.

The oval spore forms and zooids occur very frequently in the
preparations from the mid-stomach. The question as to whether they
normally develop into flagellates in this region can not be answered
as yet. The serial sections of the region show these non-flagellated
forms in the lumen when few or no nectomonads ean be detected.

The nectomonads of the mid-stomach do not show any signs of
degeneration, the nucleus has the characteristic chromatin, encrusted
nuclear membrane and central karysome (fig. 17). The cytoplasm
also is normal in appearance. The study of these forms indicates that
the first signs of degeneration of C. ewryophthalnu are to be found
in the cytoplasm. The external surface of the body is likewise free
from adherent bacteria.

The haptomonads (fig. 13) are attached to the epithelial cells in
the posterior portion of the mid-stomach. The haptomonads, or
attached forms are elongate, slender flagellates which resemble the
free nectomonad forms. The serial sections of this region show
epithelial cells lining the lumen to be intact. The cell walls are
clearly outlined with the fringe of parasites on the outside. The
cytoplasm of these epithelial cells is vacuolated but other than this
there is little indication of any degeneration of this epithelial lining.

FORMS FROM THE PYLORIC EXPANSION
In the pyloric expansion of the stomach proper the same forms
just deseribed in the mid-stomach are to be found, namely: the oval

86 University of California Publications in Z oology [Vou.18

spore, small zooid forms, the neectomonads or free flagellated forms
and the haptomonads or attached forms. The infection of this division
of the digestive tract is much greater than of any other part. It is
in this part that the infection is retained after the first infection.
The oval spore forms and zooids are readily found in nearly all the
preparations of this division of the mid-gut. There is no evidence
thus far to indicate that either the spore forms or the zooids develop
into flagellates.

Nectomonads (figs. 23-26) are found in large numbers in the
pyloric expansion. Binary fission forms (fig. 24) are found fre-
quently and this probably accounts for the reduced size of such free
forms as figures 23 or 24, and the production of the long, slender
haptomonads which will be described shortly. Figure 23 shows a
different type of nucleus which can not be regarded as being char-
acteristic of the free nectomonads. It is doubtless a sign of degenera-
tion but in these parasites it is not the most prevalent indication of
degeneration. The preparations frequently show nectomonads with
a sticky periplast. As a result of this the individuals adhere to each
other and collect many bacteria on the body surface. Many others
show the vacuolated cyotplasm or one stage farther wherein the
cytoplasm has completely degenerated leaving only the nucleus, para-
basal body, the rhizoplasts and the flagellum still attached to each
other

Haptomonads are of two general types in the pylorie expansion.
In the upper or anterior part there are found the attached, elongate,
slender forms (fig. 23) like those which occur in the posterior portion
of the mid-stomach. Gradually gradating from these long forms to
the small pear-shaped forms (figs. 20-22) are the intermediate forms.
No evidence has been found to show that the haptomonad forms
become detached and eneyst to form the oval spores. On the
contrary the cytoplasm of the haptomonad forms like that of the
nectomonad forms is vacuolate and degenerative in structure. Fur-
thermore there is no evidence that any of these nectomonads or
haptomonads normally succeed in reaching the rectum through the
intestine of Huryophthalmus convivus.

Of the three forms which migrate into the pyloric expanse the
oval spore forms are probably the true infective agents while the
nectomonads and the haptomonads are forms in degeneration.

1917] McCulloch: Crithidia euryophthalmi 87

RECTAL ForMS

In a few cases the preparations made from the rectum and con-
tents have shown a few oval spore forms (figs. 28, 35). The origin
of these is not clear but it is possible that they are zooids which have
been somewhat protected by a thicker membrane and consequently
are more resistant. As previously mentioned they retain the haema-
toxylin stain relatively longer than any of the other forms or zooids
in particular. Whether these spore forms become protected by a
thick membrane through which the stain does not readily penetrate is
an open question. Some spore forms found in rectal preparations
do not take the stain.

INFECTIVE AND DEGENERATIVE CYCLES

The question regarding the part played by the small zooids which
arise from the process of internal budding in the life cycle is of great
interest. Do they develop into flagellates or do they remain zooids,
migrating back to the posterior parts of the intestinal tract to form
the rectal spores? Preparations show that the zooids are exceedingly
numerous in the mid-stomach and pyloric expansion. Because of
their numbers and the same characteristic structure found through-
out, the zooids are regarded as infective forms. They become deeper-
staining upon reaching the rectum. All the forms which do not
remain as non-flagellated forms constitute what we have designated
the degenerative cycle. The flagellates of the mid-stomach and of
the pyloric expansion show signs of degeneration. They become
vacuolate. The nucleus may show a diffuse structure. Bacteria may
adhere to the sticky periplast or the cytoplasmic part may disappear
entirely leaving only the skeleton of the nuclear structures. No
stages of encystment of haptomonads have been observed. All the
~nectomonads and haptomonads become degenerate. Flagellated
forms in C. euryophthalmi do not become spores in so far as our
investigation has gone.

SUMMARY

1. The differences existing in the morphology and life cycles of
the two flagellates found in Leptocoris trivittatus and Euryophthal-
mus convivus have been deemed sufficient to justify our classifying
them as two distinct species, namely, C. leptocoridis and C. eury-
ophthalmi.

2. The digestive tract of Euryophthalmus convivus consists of
fore-gut divided into oesophagus and proventriculus; the mid-gut,

88 University of California Publications in Zoology [Vou.18

divided into crop, mid-stomach, and the pyloric expansion; intestine
and gland of the intestine; and hind-gut, divided into colon and
rectum.

3. The infection by flagellates usually occurs in the mid-gut in
the crop, mid-stomach, and pyloric expansion. The rectal portion of
the hind-gut has been found infected in a few instances, with spores.

4. Multiple fission is present. A few somatellae have been found
along with internal or endogenous budding.

5. The life eyele of C. ewryophthalni may be divided into two
parts, the infective cycle and the degenerative cycle.

6. The infective eyele consists of ingested spores which develop -

into large flagellates. These undergo a process of multiple fission
designated as internal or endogenous budding. Numerous small
zooids result, which migrate posteriorly and become rectal spores.

7. The degenerative cycle is made up of flagellated forms of vari-
ous sizes. Both free and attached forms from the mid-stomach and
pyloric expansion are included in this eycle.

LITERATURE CITED

DuFour, L.

1833. Recherches anatomiques et physiologiques sur les Hémiptéres, accom-
pagnées de considérations relatives 4 l’histoire naturelle et a la
classification de insectes. Inst. France, Mem. Savants Etrang., 4,
129-462, pls. 1-19.

McCuttocy, I.

1915. Outline of the morphology and life history of Crithidia leptocoridis, sp.
nov. Univ. Calif. Publ. Zool., 16, 1-22, pls. 1-4, 1 fig. in text.

Mincuin, H. A., and THomson, J. D.
1912. The rat trypanosome, Trypansoma lewisi in its relation to the rat-flea,
Ceratophyllus fasciatus. Quar. Jour. Micr. Sci., 60, 463-692, pls.
36-45, 24 figs. in text.
Parton, W. 8.
1908. Herpetomonas lygaet. Arch. Prot., 13, 1-18, pl. 1, 2 figs. in text.

_ Eee

‘Fok 16,

eee UNIVERSITY OF CALIFORNIA PUBLICATION S— (Continued)
REE ‘Vol. 15. ‘Introduction. Dependence of Marine Biology upon Hydrography and

rons rege of Quantitative Biological Research. Fp. i-xxill, June,
5: ake We ge ae 9 a AN ier Bia ce al sa ene aS eee ee Leied, Sede SS mak

1, Hydrographic, Plankton, and Dredging Records of the Scripps Institu-

tion for Biological Research of the University of California, 1901 to

2 2: Continuation of Hydrographic, Plankton, and Dredging Records of the

Scripps Institution for Biological Research of the University of Cali-—

fornia (1913-1915), compiled and arranged under the supervision o£

W: E: Ritter, by Ellis L. Michael, Zoologist and Administrative As-
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~ text, November, 1916 2... ps beens ON aed TREN aie BG Hee EU he CS ey
8. Summary and Interpretation of the Hydrographic Observations made by.

- the Scripps Institution for Biological Research of the University of

California, 1908 to 1915, by George F, McEwen, Hydrographer.
Pp. 255-356, plates 1-38. December, 1916 ........:... GaAs sieht ae erottoan a aepars=
coridis, spi nov., by Irene McCulloch. Pp. 1-22, piates 1-4, 1 text
figure. September, 1915 AME A ce EU rer EN eae aE SO Wasa aiat om
2.On Giardia microti sp. nov., from the Meadow. Mouse, by Charles

Atwood Kofoid and Blizabeth Bohn Christiansen. Pp. 23-29, 1 figure-_

in text.
3. On Binary and Multiple Fission in Giardia muris (Grassi), by Charles
Atwood Kofoid and Elizabeth Bohn Christiansen, Pp. 30-54, plates
5-8,°1 figure in text. —~ ‘
Nos. 2 and 3 in one cover, November 1915 .0.202.0.22.-.2-.-------

4. The Cultivation of Tissues from Amphibians, by John ©. Johnson.
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“6. Notes on the Tintinnoinia, 1. On the Probable Origin of Dictyocysta

tiara Haeckel. 2: On Petalotricha entzi sp. nov., by Charles Atwood
Kofoid. Pp. 63-69, 8 figures in text. December, 1915 ................ aan
- §, Binary and Multiple Fission in Hezamitus, by Olive Swezy, Pp. 71-88,
plates 9-11. i Ms
7. On a New Trichomonad Flagellate, Trichomitus parvus, from the Intes-
tine of Amphibians, by Olive Swezy. Pp. 89-94, plate 12...
Nos. 6 and 7 im one cover. December, 1915) 2. epee cee ence ovee x
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GA 6 Hs pala pen ne eatin OUROE ety AB Wali oy PR pean Tin en OE ote ee eS Tee Te A
9. Three New Helices from California, by 8. Stillman Berry, Pp, 107-

VAL. Damviary, 1916 onion eat et cece chen e ene cecetctentneteenetee
10. On. Trypanosoma triatomae, a New Flagellate from a Hemipteran Bug
from the Nests of the Wood Rat Neotoma fuscipes, by Charles Atwood
Kofoid and Irene McCulloch. Pp. 113-126, plates 14-15. February,
EGU a eS aS a ees eos hones teneentenonsmncsenvibthgenchepctee

1. The Genera Monocercomonas and Polymastiz, by Olive Swezy. Pp. 127-

~138, plates 16-17. February, 1916 1. ----2.--.--e--cee- seen pe noe ceenn nnn ae

"42. Notes on the Spiny Lobster (Panulirus interruptus) of the California

: Coast, by Bennet M. Allon. ‘Pp. 139-152, 2 figs..in text. March, 1916
18. Notes on the Marine Fishes of California, by Carl. i. Hubbs.. Pp. 153-
169, plates 18-20, March, 1916 ~.....-.1.-..-..... ASRS ECRAE NS ALS Segue ee Se ras

44, The Feeding Habits and Food ‘of Pelagic Copepods and ‘the Question

16. Cn the Life-History of a Soil Amoeba, by Charlie Woodruff Wilson.

of Nutrition by Organic Substances in Solution in the Water, by .

; Calvin O. Esterly. Pp. 171-184, 2 figs. in text. March, 1916 2... 0.2
15. The Kinetonucleus of Flagellates aud the Binuclear Theory of Hart-
mann, by Olive Swezy. Pp. 185-240, 58 figs, in text. “March, 1916...

Pp. 241-292, plates 18-23. July, 1916 ~......-- Braye tt Soc uaeeesyepeare

17. Distribution of the Land Vertebrates of Southeastern Washington, by

Lee Raymond Dice. Pp. 293-348, plates 24-26. June, 199 Gs aes

_ 18. The Anatomy of Heptanchus. maculatus ; the Endoskeleton, by J.

Frank Daniel. Pp. 349-370, pls, 27-29, 8 text figures. December,

KO Wc Spee lle tech A Gs Hale ReMi aligs eae Paes oy em aS eNO Sig eee gsi eh eee Se pa Set

19. Some Phases of Spermatogenesis in the Mouse, by Harry B. Yocom.
Pp. 871-380, pl. 30, January, L9V7 2-2 anne ose

20, Specificity in Behavior and the Relation Between Habits. in Nature
and Reactions in the Laboratory, by Calvin O. Esterly. Pp. 381-392.
March; 2997 .c305 doapnesueepvoneruaceatesartupiesetenneanehonninsesebonen PN Sean” CaS as

2.29

5e

1.00

1, An Outline of the Morphology and Life History of Crithidia lepto-

15

UNIVERSITY oF CALIFORNIA ‘PUBLICATIONS—(Contanued)

21. The Occurrence of a Rhythm in the Geotropism of. Two Species of ;
Plankton Copepods When Certain Recurring External Conditions are
Absent, by Calvin O. Esterly.. Pp. 393-400, March, 1917 2.22.20.

- 92. On Some New Species of Aphroditidae from the Coast of California, —
by Christine Essenberg. Pp. 401-430, plates 31-37. March, 1917....... 35

- 23, Notes on the Natural History and Behavior of Emerita analoga (Stimp-_ . TA

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Re AS Ly in eel re lB am Me DoS oe eB a a ns re ep ESI Cre aE CRN

24. Ascidians of the Littoral Zone of Southern California, by William E.

Ritter and Ruth A. Forsyth. Pp. 439-512, plates 38-46, August, 1917

Wol. 17. 1. Diagnoses of Seven New Mammals from East-Central California, by.
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g.. A New Bat of the Genus Myotis from the High Sierra Nevada of Cali-
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Nos. 1 and 2 in one cover. August, 1916200000
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National Park, California, by Charles Lewis Camp. Pp. 11-14. Sep-
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4, A New Spermophile from the San Joaquin Valley, California, with -
Notes on Ammospermophilus nelsoni nelsoni Merriam, by Walter P.
Taylor. Pp. 15-20, 1 figure in text. October, 1916 . Se etieetes Be
5. Habits and Food of the Roadrunner in California, by. Harold. G. Bryans, -
Pp. 21-58, plates 1-4, 2 figures in text. October, 1916 2222.2
6. Description of Bufo canorus, a New Toad from the Yosemite ‘National :
Park, by Charles Lewis Camp. Pp. 59-62, 4 figures in text. Novem-
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by Joseph Grinnell and Charles Lewis Camp. Pp. 127-208, 14 figures pe
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209-222, 2 figures in text, plate 13. October, 1917 ... 2c ieccetene
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8. Description of Some New Species of Polynoidae From the Coast of
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5. Orithidia. Euryophthalmt, sp. nov., from the Hemipteran Bug, Luryoph-
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ures. December; :3 947 so scat Sch ae

6. On the Orientation of Hrythropsis, by Charles Atwood Kofoid and —_
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7. The Transmission of Nervous Impulses in Relation to Locomotion in
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FADANY, ROUGE ace eed sa Sash ren sas woo nad sone taoo snd daeope conch ots Sadan aman bares wast -(In press).
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UNIVERSITY OF CALIFORNIA PUBLICATIONS
IN

ZOOLOGY
Vol. 18, No. 6, pp. 89-102, 12 figures in text _ December 14, 1917

ON THE ORIENTATION OF ERYTHROPSIS

BY
CHARLES ATWOOD KOFOID anp OLIVE SWEZY

(Contribution from the Zoological Laboratory and the Scripps Institution of Biological Research of the
University of California)

The dominating factors in the morphology of the Dinoflagellata
and in their evolution as a group are the two flagella. The location of
their points of origin upon the surface of the body determines the
ventral surface. The course of the transverse flagellum which pur-
sues a spiral direction in the girdle about the body delimits the epicone
and hypocone in the Gymnodinioidae and in the theeate forms sepa-
rates the epitheca from the hypotheca. The plates of the theca form
zones above and below this girdle. The proportions of the body are
profoundly influenced by the direction (ascending or descending), and
steepness of the spiral and the amount of torsion of the body which has
been developed in the direction of the stress which the activity of this
powerful flagellum creates in the girdle.

The transverse flagellum lies in a depression or girdle which has
one general direction on the body of the dinoflagellate, namely, that
of a spiral from its point of origin at the anterior flagellar pore at
the anterior junction of the girdle with the suleus on the midventral
face, transversely across the left side, thence across the dorsal surface
and around upon the ventral face to the reunion of the girdle with the
suleus. If this reunion at its distal end is posterior to the origin the
spiral is a descending left one. If it is anterior to the flagellar pore
the girdle forms an ascending left spiral. If there is no anterior or
posterior displacement the girdle forms a cirele instead of a spiral, a
condition rarely realized. The direction here described from the ven-
tral face to the left of the body and over dorsally to the right, is
universal in dinoflagellates above the Prorocentridae.

There are, in literature, seeming exceptions to this generalization.

90 University of California Publications in Zoology |Vou. 18

Fig. 1. Ceratium gravidum. Original. Dorsal surface as seen from the dorsal
side. The outlines of the ventral area and other ventral structures seen through
from the dorsal side are shown in dotted lines.

Fig. 2. The same, after Daday (1888, pl. 3, fig. 9). X 600. Showing the

1917 | Kofoid—Swezy: On the Orientation of Erythropsis 91

ventral surface drawn as though on the dorsal side with resulting reversal of
symmetry as determined by the relative sizes of posterior horns.

Fig. 3. Cochlodinium pulchellum Lebour, after Lebour (1917). X 964. Note
that the direction of the spirally twisted girdle is from the left side of the
body across to the right, that is, the girdle forms a descending right spiral. The
suleus is only partially and incorrectly drawn.

Fig. 4. Cochlodinium pulchellum Lebour, correctly drawn from life. Original.

For example, Daday (1888) described and figured Ceratiwm gravidum
with a girdle having the opposite course. This, however, is due merely
to an inadvertent oversight in observation and drawing. The ventral
area of Ceratiuwm is usually deeply impressed into the ventral face.
Viewed dorsally its outline becomes distinct as one focuses down to
secure an optical section of the midbody. If the outline of the body
is then drawn from the dorsal side and the ventral plate also drawn,
the symmetry of the organism is reversed and the girdle appears to
pass from its proximal end distally on the ventral face to the right of
the body over dorsally to the left, thus forming a right spiral instead
of a left one.

Another example of reversal of symmetry by drawing the lower
surface of the body as though it were the upper is found in Miss
Lebour’s figure (1917) of Cochlodinium pulchellum in which the direc-
tion of the girdle is reversed although in the description of the species
no notice is taken of this profound structural modification. It appears
to be only an inadvertent lapse in drawing. We have found that this
species has the normal structure at La Jolla and offer for comparison
a figure with the customary presentation of the upper surface (fig. 4)
in which there is in consequence no reversal of symmetry.

During the examination of many thousands of dinoflagellates we
have found not a single instance critically determined of such reversed
symmetry in nature, although one easily falls into the trap of making
such reversed drawings and failing to note the fact at the time. No
such reversals should be accepted as valid unless critically verified
on the living specimen showing the flagellum in action, and even then
one should be on the lookout, in Gymnodinioidae, for transverse flag-
ella thrown out of place into the anterior extension of the sulcus. It
is, of course, possible that such reversals of symmetry might occur in
nature, but evidence of their occurrence is lacking.

The so-called dextral and sinistral forms, described by Mangin
(1911) do not involve the reversal in direction of the transverse flag-
ellum and girdle above noted, but only the change from a descending to

92 University of Califorma Publications in Zoology [Vow 18

an ascending spiral. It is not therefore such a reversal as that noted
in the figures of Daday (1888) and Lebour (1917) and involved in
the orientation of Erythropsis proposed by Fauré-Fremiet (1914).
The transverse flagellum and the girdle have important and fixed
relations to the process of binary fission. The fission plane passes

Fig. 5. Ventral view of Ceratiwm furca. X 706. In this and the following
figure the apical plates are numbered 1’-4’, the precingulars 1”-4”, the post-
cingulars 1”’-5’”’, the antapicals 1””-2””, and the girdle plates 1-4; att.ar.,
attachment area; fiss.l., fission line; v.a., ventral area.

Fig. 6. Dorsal view of C. furca. X 706.

through the point of origin of the transverse flagellum and cuts across
the girdle obliquely from the right anteriorly to the left posteriorly,
parting the theea along definite suture lines (figs. 5, 6).

This plane has this oblique position in the dinoflagellates generally
except in the Prorocentridae and the Dinophysidae. A reversal of

1917 | Kofoid—Swezy: On the Orientation of Erythropsis 93

symmetry such as that induced by a change in the direction of the
girdle as described above must be accompanied by an internal reor-
ganization of the nucleus, mitotic figure, and fission plane, as well of
of the exoskeleton and furrows. This reorganization would involve a
shift of axes and attendant internal morphogenic factors of about 90°
from the left over to the right.

Fig. 7. Ventral view of two schizonts of Ceratium in chain. After Kofoid
(1909, pl. 1, fig. 1, two anterior schizonts and apical horn of the third). Note
apical pore of-horn of posterior schizont lodged against the attachment area
of the anterior schizont. X 405.

Fig. 8. Daughter schizonts of Cochlodinium citron sp. nov. in chain, with
apical region of the posterior schizont applied to the region of the end of the
girdle of the other. X 937.

Such a profound reorganization as this should be proven beyond
suspicion before it may be accepted. The place of origin and direction
of the transverse flagellum in Erythropsis as figured by Fauré-Fremiet
(1914), if the body is oriented as it is by all other observers of this
organism, presents just such a reversal of symmetry.

94 University of California Publications in Zoology (Vou.18

A second feature of the relations of this girdle to the organization
of the dinoflagellates is the fact that the point of contact of anterior
and posterior schizonts in chain formation, or at binary fission, is at
the distal end of the girdle of the anterior cell and the apex of the
posterior one (figs. 7,8). The apical pore at the anterior tip of the
posterior daughter cell is thus in direct protoplasmic continuity with
the anterior cell at the distal end of the girdle. Its shaft les in a
channel below the girdle and its tip is thrust against the anterior
shelf or lip of the girdle. When the schizonts part, this depression
persists for some time as an attachment area (att. ar., fig. 5) but may
ultimately fade away. It appears that Fauré-Fremiet (1914) has
interpreted this attachment area, or a region near it, at the distal end
of the girdle as the flagellar pore of its proximal end in Erythropsis.
The apical horn of Ceratiwm is modified to fit the attachment area
(fig. 7) and this modification persists for some time after the detach-
ment of the schizonts. The apex of Erythropsis is homologous to this
apical pore of Ceratiwm and may be expected to detach from the
attachment area at binary fission, as well as to undergo some readjust-
ment after detachment.

The relationships of two schizonts in chain in Cochlodinium citron
are shown in figure 8. In ease of the reversal of symmetry and orien-
tation proposed by Fauré-Fremiet (1914) for Erythropsis, the adjust-
ments necessitated in chain formation would be considerable. The
proposed orientation provides neither attachment area nor apical
point.

It has not infrequently been the fate of rare and at the same time
peculiar or novel organisms to be strangely or even absurdly misinter-
preted. Thus Nitzsch (1817) deseribed a Ceratiwm as a Cercaria and
Uljanin (1870) interpreted Polykrikos as a Turbellarian, and the larva
of the Syrphid fly Microdon was described as a mollusk.

Such misfortune has attended few organisms so persistently as it
has the ill-starred Erythropsis, a unique genus of the Dinoflagellata,
in which there has developed a remarkable stigma or ocellus with amoe-
boid melanosome, hyaline laminate lens, and pigmented sensory ( 2)
core or end organ, as well as a highly specialized, remarkably active,
protrusible and retractile prod (tentacle, Hertwig (1884), dart, Fauré-
Fremiet (1914) ), directed posteriorly from a ventro-posterior recess
(eset. 12);

Up to the time of Fauré-Fremiet’s observation (1914) only six
individuals of the remarkable genus had been reported. In most, if

ge EEE Cee etl oon

ee

me ~e a.

1917 | Kofoid—Swezy: On the Orientation of Erythropsis 95

not all, of these cases the period of observation was brief in as much
as the animal quickly drops its prod and undergoes cytolysis shortly
thereafter, when exposed to the stimulus of the brilliant illumination
of the microscope.

The first individual was found by the eminent Russian biologist,
Elie Metschnikoff, who found it amid plankton débris taken off
Funchal in the Madeira Islands in 1872. In a brief note (in Russian)
he (1874) called attention to its possible relationships to the Suctoria,
but neither deseribed nor figured it. Ten years later the greatest of
German protozoologists, Professor Richard Hertwig, then of Bonn
University, found a single individual in the plankton of the Mediter-
ranean at Sorrento. It dropped its prod soon after its capture, but
was thereupon fixed in osmic acid and preserved in mutilated and dis-
torted form as a microscopical preparation. From this abnormal frag-
ment Hertwig (1884) deseribed ‘‘Erythropsis agilis, eine neue Pro-

9?

tozoe,’” making the comparison of the prod to the stalk, and noting
the similarity of its anterior part to the peristomal region of a vorti-
eellid ciliate. However, he explicitly notes the absence of cilia and the
presence of a spiral filament wound about the anterior end. He did
not, however, suggest any relationship of his unique organism to the
flagellates or to the Dinoflagellata.

Immediately upon the publication of Hertwig’s account, the veteran
zoologist, Carl Vogt, of Geneva, attacked (1885a) the validity of the
organism and called upon all zoologists to deny it admission to the
category of beasts on the ground that it was only a detached zooid of
a marine vorticellid, Spastostyla sertulartarum Entz, which had eaten
thé eye of a medusa, Lizzia or Nausithée. Hertwig replied (1885)
clearly setting forth the characters of Erythropsis which made Vogt’s
interpretation untenable; but the latter was unconvinced, returning
(1885b) to the fray with a deadly array of parallel figures in which he
reproduced Hertwig’s figure with the evidence of the error by Hert-
wig made the more convincing by the substitution in his copy of the
figure of Erythropsis of a row of membranelles for Hertwig’s spiral
thread and the introduction of an axial fibre in the stalk-like prod or
tentacle.

This discussion brought Metschnikoff (1885) to the support of
Hertwig who recalled his brief note (1874) on the organism of a decade
prior, expressed his confidence in the authenticity of the organism and
allied it with the suctorian Ophryodendron.

The cloud of suspicion thus cast upon Erythropsis may or may

96 University of California Publications in Zoology [Vou.18

not have been responsible for its subsequent complete disappearance
from the literature of protozoology. The articles pertaining to it were
in part published in the Zoologischer Anzeiger, the most widely dis-
tributed zoological journal in the world. But Biitschli in his Thier-
reich monograph of the Protozoa, then in process of publication (1883—
1889), omits all reference to Erythropsis. Pouchet who published in
France a series of papers on dinoflagellates and rediscovered the
ocellus in organisms now referred to Pouchetia, a genus closely related
to Hrythropsis, makes no note of Hertwig’s species. Neither does
Sehutt in his Plankton Expedition monograph (1895) note its exist-
ence, although he describes, as Pouchetia cornuta and P. cochlea, two
species which belong to the genus Erythropsis. This relationship, how-
ever, was in part obscured by the reduction or absence of the prod in
Schiitt’s specimens. The ocellus, it would seem, was sufficient to have
established the relationship. In his later (1896) assemblage of the
genera of the ‘‘Peridiniales’’ in Engler and Prantl’s P/flanzenfamilien,
Erythropsis 1s again missing.

It was not until Delage and Hérouard (1896) assembled the Pro-
tozoa in their T'raité de Zoologie Concrete that the genus was recogn-
ized as valid and placed in its true relationship. These authors,
impressed by its similarity to Pouchetia, cautiously admitted it into
an appendix to the Dinoflagellata.

They fell, however, into one misrepresentation of Hertwig’s figures,
which affords the starting point for Fauré-Fremiet’s later erroneous
allocation of the flagellum. In discussing the girdle and its flagellum
they state:

Le filament en ressort 4 boudin n’a rien de commun avee une zone adorale
tandis qu’il représente exactement le fouet transversal d’un Peridinien (il faut
noter cependant que Hertwig n’est pas trés affirmatif sur la question de savoir
si la portion qui occupe la gouttiére est ou non continue avec celle qui est logée
dans la partie supérieure du sillon longitudinal, et que ce fouet, par une exception

unique, suivrait le sillon de gauche & droite. Enfin le gros appendice serait le
fouet vertical). ;

The basis for this interpretation is not clear as will be seen in our
reproduction of Hertwig’s (1884) figures (figs. 9,10). In so far as
the main encircling spiral filament, as shown in the figures, is con-
cerned, it might run in either direction around the body, for as a
matter of fact, neither end is figured, and the short strand seen in one
of Hertwig’s figures (pl. 6, fig. 2, reproduced in our figure 10), may
be the amoeboid uppermost end of the suleus and not a flagellum
connected with any part of the girdle.

1917 | Kofoid—Swezy: On the Orientation of Erythropsis 97

In the previous year Schiitt (1895) had figured two species which
he called Pouchetia cochlea and P. cornuta. Both had the ocellus, as
have other species of Pouchetia, but in neither one did Schiitt detect
the prod, although he figures it in P. cornuta as hidden in the poste-
rior recess, but leaves it unnamed and unnoted. Owing to this record
and to his discovery of the paradinial lines (fig. 12, par.l.) along
the girdle, not seen by Hertwig (1885) but now known to be char-
acteristic of the genus, his figures of P. cornuta have been referred to
Erythropsis by Pavillard (1905) and Fauré-Fremiet (1914).

Schutt’s figures (1895, pl. 26, figs. 96, 1, 2, reproduced in our
figure 12), continue and confirm the previous confusion regarding
the location of the anterior flagellar pore. In these figures the girdle,
instead of arising at a junction with the suleus above the ocellus, comes
down from the apical horn. The upper end of the suleus is thus con-
fused with the proximal end of the girdle.

In 1905 Pavillard had the opportunity to inspect for a brief period
another specimen which he referred to Hertwig’s Erythropsis agilis
and presented for the first time an adequate sketch from life of the
entire animal, but he also figures the transverse flagellum as running
up this apical horn.

Collin (1912) records the discovery of another specimen of
Erythropsis in the student laboratory at the Biological Station at
Cette and Fauré-Fremiet (1914) states that Chatton had seen another
at Banyuls-sur-Mer.

Thus up to the time that Fauré-Fremiet (1914) saw his ‘‘ving-
taine’’ of specimens at Croisic on the west coast of France in the sum-
mer of 1913, not more than six specimens of this peculiar and puzzling
organism had been seen.

Whatever doubt and suspicion may have persisted as to its validity
had been made entirely untenable by Pavillard’s account, but the point
of origin and the course of the transverse flagellum were still unde-
termined, and the presence or not of a longitudinal flagellum in addi-
tion to the prod was problematical. A peculiar stout flagellum-like
structure was figured by Schiitt (1895) for P. cornuta, but the presence
of a prod or tentacle in this species was not clearly established.

In 19138 Fauré-Fremiet published a brief note recording Ery-
thropsis from the west coast of France and followed this with a fuller
account than anyone has yet made of this remarkable organism. In
his later paper (1914) he orients it (fig. 11) with the prod anterior,
the ocellus directed posteriorly, and the apical end as the antapical. —

98 University of California Publications in Zoology [Vou. 18

Fig. 9. Ventral view of Erythropsis agilis Hertwig. After Hertwig (1884).

Fig. 10. Dorsal view of Erythropsis agilis Hertwig. After Hertwig (1884).

Fig. 11. Ventral view of Erythropsis agilis Hertwig. After Fauré-Fremiet
(1914, fig. la). Orientation as proposed by Fauré-Fremiet.

Fig. 12. Ventral view of Lrythropsis cornuta (Schiitt). X 530. Original.
Orientation based on locomotion. ap. pr., apical process; g., girdle; 1., lens; mel.,
melanosome; n., nucleus; oc., ocellus; par.l., paradinial lines; pr., prod; pus.,
pusule; rec., recess for prod; sul., sulcus or longitudinal furrow; tr. fl., transverse
flagellum.

1917 | Kofoid—Swezy: On the Orientation of Erythropsis 99

He furthermore concludes that the transverse flagellum takes its orgin
at the region which we interpret as the attachment area. If we orient
the body in the usual position the girdle and flagellum would thus
form an ascending right spiral instead of a descending left one and the
symmetry of these two fundamental structures, the girdle and flag-
ellum, would be reversed.

The grounds upon which this interpretation rests appear to be
‘“‘logical’’ rather than observational. There is no evidence in Fauré-
Fremiet’s account that he had correlated his orientation with the loco-
motor activities of the animal. He does not state that he has seen it
advanee prod first and with the ocellus directed posteriorly. He figures
(fig. la, reproduced in our fig. 11) a small longitudinal flagellum
emerging from the apical process, but states in his text ‘‘les données
relatives a son existence elle-méme sont malheureusement insuffisants.”’

During the past summer we have seen at the Marine Laboratory
of the Seripps Institution at La Jolla, California, in the plankton
taken five miles off shore a number of individuals of Hrythropsis
and have noted its mode of progression and its orientation. The
animal progresses mainly in anti-clockwise circles with some rota-
tion about its major axis. During locomotion its prod is directed
posteriorly ; the ocellus anteriorly. Moreover, the transverse flagellum
(fig. 12) takes its origin at the flagellar pore at the point where the
girdle joins the suleus anteriorly and passes in the usual direction of
a descending left spiral about the body in the transverse furrow. As
cytolysis approaches, it shortens up and may be thrown out of the
furrow towards the apex. It does not arise at the distal end of the
girdle as figured and described by Fauré-Fremiet. There is, however,
_at the distal end on the anterior margin of the girdle a notch with a
pit-like depression which we interpret as the attachment area. It is
not a flagellar pore either posterior or anterior.

The longitudinal flagellum does not emerge at the apex although
the transverse one may be temporarily thrown towards that region,
and the area itself at times may appear to have local amoeboid move-
ments in the region of the tip of the suleus which passes anteriorly
upon the epicone. The longitudinal flagellum is found, as figured by
Schiitt (1895, pl. 26, fig. 96), emerging from the posterior chamber
or recess surrounding the base of the prod. From this region, as also
from the anterior flagellar pore there passes into the cytoplasm the
characteristic pusule.

100 University of California Publications in Zoology [Vou. 18

SUMMARY

We conclude therefore on the basis of the examination of the evi-
dence from the comparative structure of Erythropsis and other Dino-
flagellata that the prod of Erythropsis is directed posteriorly, not ante-
riorly, that the girdle is anterior, not posterior in location, and that
the ocellus is directed anteriorly, not posteriorly. Likewise that the
transverse flagellum takes its origin at the anterior junction of girdle
and suleus at the proximal end of the girdle and not at the attachment
area at its distal end.

We also confirm Schiitt’s (1896) findings as to the presence of a
posterior flagellum in addition to the prod, arising in the chamber
about the base of that organ and projecting posteriorly. These con-
clusions from the standpoint of comparative anatomy are supported
by our observations on the locomotion of the hving organism. Fauré-
Fremiet’s (1914) orientation of the animal with the prod anterior
and his account of the origin and course of the flagella must be rejected
as untenable.

Transnutted December 1, 1917.

ZOOLOGICAL LABORATORY,
UNIVERSITY OF CALIFORNIA,
BERKELEY, CALIFORNIA.

1917 | Kofoid—Swezy: On the Orientation of Erythropsis 101

LITERATURE CITED

BuUTScHLI, O.

1883-1889. ‘‘Protozoa’’ in Bronn’s Klassen und Ordnung des Thierreichs,

i= 20305) plss 1-79:
CoLuin, B.

1912. Etude monographie sur les acinétiens. II. Morphologie, physiologie,
systematique. Arch. de Zool. Exp. et Gén., 10, 1-457, pls. 1-6, 111
figs. in text.

Dapbay, E.

1888. Systematische Uebersicht der Dinoflagellaten des Golfes von Neapel.

Term, Huz., 11, 98-109, pl. 3.

DELAGE, Y. and HEROUARD, E.
1896. Traité de zoologie concréte. (Paris, Schleicher Fréres), 1, xxx + 584,
890 figs. in text.

FAURE-FREMIET, E.
1913. Sur l’Hrythropsis agilis R. Hertwig. C.R. Acad. Sei. Paris, 157, 1,019-
1,022.
1914. Lrythropsis agilis. Arch. Prot., 35, 24-45, pl. 1, 12 figs. in text.

HERTWIG, R.
1884. Hrythropsis agilis, eine neue Protozoe. Morph. Jahrb., 10, 204-212
+1, pl. 6. Not Arch. mikr. Anat., as cited by Fauré-Fremiet (1914).
1885. Ist Hrythropsis agilis, eine losgerissene Spastostyla sertulariarwm?
Zool. Anz., 8, 108-112.

Kororp, C. A.
1909. Mutations in Ceratium. Bull. Mus. Comp. Zool., Harvard, 52, 211—
257, pls. 1-4, 5 figs. in text.

LEBouR, M. V.
1917. The Peridiniales of Plymouth Sound from the region beyond the
breakwater. Jour. Marine Biol. Assoc., 11, 183-200, 14 figs. in
text.

MANGIN, L.
1911. Sur l’existence d’individus dextres et sinistres chez certains Peri-
diniens. C.R. Acad. Sci. Paris, 153, 27-32, 5 figs. in text.

METSCHNIKOFF, E.
1874. Mittheilungen iiber eine Reise nach Madeira. Rep. Imp. Soc. Friends
Nat. Hist. Anthrop. Ethn., Moscow, 10, no. 2, pp. 6-9.
1885. Zur Streitfrage tiber HLrythropsis agilis. Zool. Anz., 8, 433-434.

Nirzscu, C. L.
1817. Beitrag zur Infusorienkunde oder Naturbeschreibung der Zerkarien
und Bazillarien. Neue Schr. d. nat. Ges. zu Halle, 3, viii+128, 6 pls.

PAVILLARD, J.
1905. Recherches sur la flore pélagique (phytoplankton) de l’Btang de
Thau. Mem. Univ. Montpellier (série mixte), 2, 1-116, 1 chart,
pls. 1-3.

102 University of California Publications in Zoology (Vou. 18

Scutrt, F.
1895. Peridineen der Plankton-Expedition. Ergebnisse der Plankton-Expe-
dition der Humboldt-Stiftung, 4 M a A, 1-170, pls. 1-27.
1896. ‘‘Peridiniales’’ in Engler and Prantl Die natiirlichen Pflanzen-
familien. (Leipzig, Engelmann), 1, 1-30, 43 figs. in text.
ULJANIN, O. W.
1870. On the pelagic fauna of the Black Sea. Rep. Imp. Soc. Friends Nat.
Hist. Anthrop. Ethn., Moscow, 8, no. 1, pp. 57-62 (in Russian).

Voert, C.
1885a. Ueber Erythropsis agilis Rich. Hertwig. Zool. Anz., 8, 153.
1885b. Ein wissenschaftlicher Irrthum. Die Natur, 34, 183-187, 5 figs. in

text.

—.

UN IV ERSITY OF CALIFORNIA PUBLICATION &— (Continued)

Bh 15. Introduction. Dependence of Marine Biology upon Hydrography snk

Necessity of Quantitative Biological carmen Pp. i-xxiii. June,
iY SSeS SSSR NE ges Sus ARR GIL sly eer ER SOREN Mansa Te pak gee SR OC
a Hydrographic,. ‘Plankton, and Dredging Records of the Scripps Tnstita-
: tion for Biological Research of the University of California, 1901 to
1912; compiled and arranged under the supervision of W. E. Ritter

by Ellis L. Michael and George F. McEwen. Pp. 1-206, 4 text figures -

DIIGs MAD ING, SOLO cg oc ers ot Se eS eat Np es

2. Continuation of Hydrographic, Plankton, and Dredging Records of the
‘Scripps Institution for Biolocical Research of the University of Cali-
fornia (1913-1915), compiled and arranged under the supervision of

W: E. Ritter, by Ellis L. Michael, Zoologist and Administrative As-
sistant, George F. McEwen, ‘Hydrographer. Pp. 207-254, 7 figures in
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Fol..16. 1. An Outline of the Morphology and Life History of Crithidia eo

coridis, sp. nov., by Irene McCulloch, Pp. 1-22, plates 1-4,°1 text
igure. Dept ben, VOT ae ee stg ee cee
2. On Giardia microti sp. nov. from the Meadow Mouse, by Charles
Atwood Kofoid and ‘Elizabeth Bohn Christiansen. Pp. 23- 29, 1 Seas
>in text.
8, On Binary and Multiple Fission in-Giardia muris- (Grassi), by Charles
Atwood Kofoid and Elizabeth Bohn Christiansen, Pp. 30-54, plates
58, 1 figure in text.
WNos..2 and 3 in one cover, November. 1915... .-20 on
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6. Notes on the Tintinnoina. 1. On the Probable Origin of Dictyocysta
~ tiara Haeckel. 2.°On Petalotricha entzi sp. nov., by Charles Atwood
Kofoid. Pp. 63-69, 8 figures in text... December, 1915 2.0.
6, Binary and Muitiple Fission-in- Hezamitus, by Olive Swezy. Pp..71- 88,
plates 9-11.
7, On a New Trichomonad Flagellate, Trichomitus parvus, from the Intes-
tine of Amphibians; by Olive Swezy. Pp. 89-94, plate 12. .
Nos, 6 and.7 in one cover. December, 1915 22k
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A adr ates See a Br Ne arin eee ie, NR apron a a eee ed
9. Three. New Helices from California, by S. Stillman Berry. Pp. 107-
Nisare ATT 5 PIVUCRT Vy SPO oe es oak adc dae Pega Cattaneo eee Goede erate
-10.On Trypanosoma triatomae, a New Flagellate from a Hemipteran Bug

from the Nests of the Wood Rat Neotoma fuscipes, by Charles Atwood *

Kofoid and Trene McCulloch. Pp, 118-126, plates 14-15. February,

ESR ae ee Se fe eek os nate eg eer ne, 6M

11. The Genera il pave tootonas and Polymastix, py Olive Swezy.. Pp. 127-

138; plates 16-17. February, 1916 oon a a ree

12, N otes on the Spiny Lobster (Panulirus interruptus) of the California

~ Coast, by Bennet M. Allen. Pp. 139-152, 2 figs. in text. March, 1916

18. Notes on the Marine Fishes of California, by Oarl Ly. Hubbs. Pp. 153-
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44, The Feeding Habits and Food of Pelagic Gopepods and the Question

of Nutrition by Organic Substances in Solution in the Water, by

: Calvin O. Esterly. Pp. 171-184, 2 figs. in text.. March, 1916... es

15. The Kinetonucleus of, Flagellates and the Binuclear Theory of Hart-

-. Mann,-by Olive Swezy. Pp. 185-240, 58 figs: in text. March, 1916...

16. Cn the Life-History of a Soil Amoeba, by Charlie Woodruff. WASOR. 3

“Py 24-2087 pintes 86-235: duty: LONG. sabe oe a
17. Distribution of the Land Vertebrates of Southeastern Washington, by

Lee Raymond Dice:.. Pp. 293-348, plates 24-26. June, 1916 x...
18. The Anatomy of Heptanchus maculatus; the Endoskeleton, by J.

Frank Daniel. Pp. 349-370, pls. 27- ag 8 text figures. December,

19. Some Phases of Spermatogenesis in the Mouse, by Harry B. Yocom,
EP SL EORO, Dis DO cs SATO AL YS LOL La este ang ea peecc eanen ogrtwasece
20, Specificity: in Behavior and the Relation “Between Habits in Nature
and Reactions in the Laboratory, by Calvin oO. sspatly: r? 381-392,
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21. The Occurrence of a Rhythm in the Géotropism of Two peabinn of ee xe
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22. On Some New Species of Aphroditidae from the Coast.of Galifornia, ey
by Christine Essenberg. Pp. 401-430, plates 31-37, March, 1917....... oo
23. Notes on the Natural History and Behavior of Emerita analoga (Stimp- age
son), by Harold Tupper Mead. Pp. 431-438, 1 text figure. Apri i
BDF sa eo Sg a tasted page aua ue Saree sane dap Duane ae gE OS eal Sees TEN skate
94. Ascidians of the Littoral Zone of Southern California, by William. E.
Ritter and Ruth A. Forsyth. Pp. 439-512, plates 38-46. August, 1917

VoL 17. 1. Diagnoses of Seven New Mammals from East-Central California, by
Joseph Grinnell and Tracy” I, Storer, Pp. 1-8.
2. A New Bat of the Genus Myotis from the High Sierra N evada. of Call-
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p(y 204s) AE £2 NI ¢ Ranta eae cre Sapte ANS 9” S/O ak noua we Sa uO as SER ES ope na hs Wepedir abe
4, A New Spermophile from the San Joaquin Valley, California, With :
Notes on Ammospermophilus nelsoni. nelsoni Merriam, by Walter P.-
Taylor... Pp. 15-20, 1 figure in text.. October, 1916.02. 2.
5. Habits and Food of the Roadrunner in California, by Harold OC. Bryant,
Pp. 21-58, plates 1-4, 2 figures in text. October, 1916.-......--. 2...
6. Description of Bufo canorus, a New Toad from the Yosemite National
Park; by Charles Lewis Camp. Pp. 59-62, 4 figures in text. Novem." :
Hi You Gael 2 Yb Pb ste aA cat ae sR sce ante cia My case VAMC ak en GE LSS mse Ne Posen rahe 5a NSPE ;
7. The Subspecies of Sceloporus occidentalis, with Description of a New.
Form: from the Sierra Nevada and Systematic Notes on Other ,Cali-
fornia Lizards, by Charles Lewis Camp, Pp. 63-74. December, 1916 ~
. Osteological Relationships of Three Species of Beavers, by F. Harvey
Holden. Pp. 75-114, plates 5-12, 18 text figures. March, 1917 .......... i
. Notes on the Systematic Status of the Toads and Frogs of California,
by Charles Lewis Camp. Pp. 115-125, 3 text figures. February, 1917 — -
10.-A. Distributional List of the Amphibians and Reptiles of California,
by Joseph Grinnell and Charles Lewis Camp. Pp. 127-208, 14 figures
The Gerba: eB YON Ge as a a So ese a len cn cael tins
11..A Study of the Races of the White-Fronted Goose (Anser aibiftons)
Occurring in California, by H.S,. Swarth and, Harold C. Bryant. Pp.

Oo oo

209-222; 2: figures in text, plate’13. October, 1917 2.2. a
Vol. 18... 1. Mitosis in Giardia Microti, by William C. Boeck. Pp. 1-26, plate 1. :
OCU OL, LING a ae 5 en ce atic ayaa nadebciggena Napoca

2. An Unusual Extension of the Distribution of the Shipworm. in San
Francisco Bay, California, by Albert L. Barrows. Pp. 27-43: De-
cember, BORD Bo ey ae SS ee ah Lo ee ce toe

3. Description of Some New Species of Polynoidae From the Coast of
California, by Christine Essenberg. Pp. 45-60, plates 2-3. October,
OUT sR a as ected ah aaa RCL og de oa nike IEE hae de OES

4. New Species of Aphinomidae. From the. Pacific Coast, by Christine 2 3
Essenberg. »Pp. 61-74, plates 4-5. October, 1917....0...22201 ke sho

5. Crithidia Euryophthalmi, sp. nov., from the Hemipteran Bug, Euryoph- as
thalmus Convivus Stal, by Irene McCulloch. ED: 76-88, 35 text fig- ae
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6. On the Orientation of Brythropsis, by Charles Atwood Kofoid and : _
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UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN
ZOOLOGY
Vol. 18, No. 7, pp. 103-134, 14 figures in text January 7, 1918

THE TRANSMISSION OF NERVOUS IMPULSES
IN RELATION TO LOCOMOTION
IN THE EARTHWORM

BY
JOHN F. BOVARD

CONTENTS
PAGE
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TEs \AVOelis one LETC G ESTs 0 (eh ee ee Se eee ee een EEE eee ee ee 104
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2. Anesthesia method by ether and nitric acid -.............------------- 107
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TEV OUP aE SAAT oS eR ae Re Er ee ee ro 108
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Experiments with anesthetized worms ..............-----------.--0--c--c0-0eeceeceeeee erences 108
Thy ERREXSy TERA? ETC Tae nO Se Serna re er Ee error 109
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AW Ubaiiemvitifgy GE TARE NSTOMISINON, So. oe cec cece ese eee eecce dace] ae ee no: ce erence ea eeeEeceE EE aA E REECE 118
VI. Dependence on the nervous system for transmission -.....-.......-.-.-.-..-. 120
Wil, Rateot transmission of locomotor impulses) 22-22 2 122
VIII. Rate of transmission of giant fiber impulses ................-..--------------------- 125
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104 University of California Publications in Zoology [Vou 18

INTRODUCTION

The normal creeping movements of the earthworm proceed as fol-
lows. The first movement is a contraction of the circular muscles of
the first few segments. This causes an extension of the anterior end.
The chaetae now become directed backwards and take hold on the
substrate while the longitudinal muscles begin a contraction which
draws the next few segments forward. The circular muscles in each
segment contract, one segment after another beginning at the anterior
end and proceeding posteriorly. Immediately following the circular
muscle action the longitudinal muscles contract so that a wave of
extension followed by a shortening can be seen to traverse the whole
animal. After the first wave of muscular activity is well started
posteriorly another may be initiated and at any one time several of
these contraction waves may be seen in a normally creeping worm.

Some years ago Friedlander (1894) showed that in the normal
creeping of an earthworm the nervous system played only a small part.
When a section of the nerve cord containing ten to twelve ganglia was
removed, the movements of the parts of the worm were still perfectly
coordinated. The most important part of the activity was the ‘‘pull’’
which the contraction of each segment as the wave progresses gave to
the succeeding segments. The wave-like motion of the contractions
proceeding down the length of the animal was due, first, to the pull
of segments on each other, and, secondly, to the sequence of reflex
actions of the nerves in each segment, which are such that the longi-
tudinal muscles follow the contractions of the circular muscles. This
nervous mechanism is, according to Friedlander, concerned with each
segment alone, and there is no passage of impulses up or down the
cord. No attempt was made by him to analyze the matter of tension
or pull, or to determine whether codrdination would proceed without
this factor. .

Tn order to show that the nervous system was entirely secondary,
Friedlander cut a worm into two pieces and then joined these two with
a thread The creeping movements of the anterior piece gave the
necessary pull on the posterior piece through the thread, and the two
parts crept along in perfect codrdination. In certam special cases,
when the nerve cord was destroyed for a short distance without tran-
section of the body, the parts anterior and posterior to the cordless
region moved together with perfect codrdination. According to this

1918] Bovard: Nervous Impulses in the Earthworm 105

view, then, the nerve cord is supplementary and concerned only with
those short reflex paths which are mediated by a single ganglion.
Previous to the year in which Friedlander published his analysis of
the movements of earthworms, Krukenberg (1881) showed, in some
work on leeches, that the middle section of the animal could be
anesthetized with the result that the parts anterior and posterior to
this region still acted in perfect codrdination. In these animals, how-
ever, the nervous system differs structurally from that of an oligo-
ehaete. In leeches the nerves run from the anterior to the posterior end,
while in the oligochaetes the only long nerves are the giant fibers, the
other fibers in the cord being those of short neurones extending at
most from one ganglion to the next. The anesthesia in leeches affects
only the peripheral nerve endings, while the trunks connecting anterior
and posterior portions are not affected.

The more recent work of Biedermann (1904) becomes particularly
interesting, however, as it gives some new light on the function of the
nerve cord of the earthworm. In this work on the comparative physi-
ology of peristaltic movements he compares the locomotor action in
earthworms to the rhythmic movements found in smooth muscle.
Biedermann discovered that if worms were placed in seven per cent
aleohol for a few minutes until they became motionless and then the
middle region of several segments was anesthetized with nitric acid or
pure chloroform for a few seconds, the muscular activity of the sec-
tion was destroyed and all response to stimulus failed. He then had a
worm with active anterior and posterior parts connected through the
anesthetized area by a nerve cord. In creeping movements, the
anesthetized area, or dead area, acted as one piece. It transmitted
no rhythmic movements, while the posterior part still acted in perfect
coordination with the anterior part.

In further tests by Biedermann of the transmission of impulses
through: the cord over more than one segment, he pinned such anes-
thetized specimens to a cork plate by needles through the dead mus-
cular area and found that the posterior part still moved in perfect
coordination with the anterior part. With regard to the limits of this
transmission through the cord, and the speed of the impulses, it is
stated in his paper (1904, p. 493) that the transmission often runs
2-3 centimeters in 4-5 seconds.

In the interpretation of these experiments Biedermann accepts the
theory proposed by Friedlander, except that in order to explain the
coérdinated movements of posterior pieces when a certain part was

106 University of California Publications in Zoology [Vou. 18

anesthetized, it is necessary to assume that the impulses run through
the cord for a considerable distance rather than through one ganglion
as Friedlander supposed.

MATERIALS AND METHODS

Materials—Several species of worm were used for these experi-
ments. The large garden worm, Helodrilus caliginosa, was favorable
material owing to its size. The small dung worm, Allolobophora
foetida, was also very convenient material because of the ease of
obtaining the material during the winter. No difference was observed
in the reactions in these worms. Unless specially noted the experi-
ments recorded will refer to the larger worm, Helodrilus.

Methods—Biedermann’s (1904) method of anesthetizing a cer-
tain portion of a worm by use of nitric acid or chloroform, as described,
had the effect of killing any peripheral nerve endings present in the
part and of impairing the muscle cells. It left the anterior and pos-
terior portions connected, however, by a functioning nerve cord, still
intact, except that no stimuli applied to the treated epithelium were
effective in setting up reflexes.

It was suspected by Biedermann that as locomotion took place the
posterior part was acting in codrdination, not only because it was
connected to the anterior, as Friedlander might have supposed from
his string experiment, but that there was some real nervous influence
transmitted by the cord in the inert middle section. In order to test
this point fully, he pinned the middle anesthetized portion to a cork
plate to remove the factor of tension, when it was found that the
posterior portion still made movements coédrdinated with those of the
anterior piece. This established beyond a doubt that transmission
did take place over a longer section of the cord than the earlier in-
vestigators had deemed necessary and showed the more important part
played by the nervous system.

In developing a method of anesthesia to test farther the matter of
transmission, it seemed to me desirable to find some means of blocking
reflexes in the middle area, and yet it was also quite necessary at the
same time to leave the muscle tissue and the central nerve cord intact,
only the peripheral nervous system being eliminated. The method
developed was quite different from that of Biedermann. The worm
was placed on a glass plate slightly moistened with water, so that it
was slippery. A small four-drahm homeopathic vial containing some

1918] Bovard: Nervous Impulses in the Earthworm 107

cotton soaked with ether, was then turned down over the worm so that
the mouth of the bottle covered the middle section of the worm. It
was possible to hold this in place over the squirming worm until the
middle part was anesthetized. Owing to the slipperiness of the plate,
the worm could get no hold and autotomy was very rare. When,
however, as occurred in early experiments, this method was tried on a
cork plate, autotomy of the anterior or posterior part was frequent
because of the hold the chaetae were able to take on the cork and so
the worm could pull itself in two. Exposure of two minutes to ether
fumes was sufficient for complete anesthesia, but had little effect on
the muscle tissue itself. The worms usually recovered completely from
the effects of the treatment in from ten minutes to an hour. During
this time a stimulus to the muscle in the anesthetized area called forth
a direct response but started no reactions in the untreated parts of
the worm.

In using some of the larger worms this simple method was varied
by treating the etherized area with six per cent nitric acid for ten
seconds, then washing the whole worm in water; this made certain
that the sensory nerve endings, of this part, were rendered functionless.
In cases where nitric aid was used the worm never recovered from the
treatment, and in a few cases where the worms were kept for a few
days they autotomized the posterior and middle sections. This method
was used where only a nerve bridge was desired between the active
anterior and posterior parts, as in measuring the speed of transmission

of impulses in the nerve cord.

STATE OF THE ANESTHETIZED AREA

_ For a very short period after treatment, the anesthetized section
looks whitish and gives off a great deal of mucous, but later the appear-
ance is much the same as that of the rest of the worm, except for an
inerease in diameter. As the worm begins active movement, this
middle piece decreases in diameter, due to stretching, for it acts much
like a rubber band, extending and then contracting with each creeping
movement. However, no waves of muscular contraction run along
its length, as in the anterior and in the posterior parts, or from the
former to the latter.

Stimulation of a quiescent worm in the anesthetized and live
regions respectively gives a marked difference in response. If the
anterior part is touched lightly the response is an increase in diameter
due to a reflex stimulation of the longitudinal muscles, but a stimu-

108 Umversity of California Publications in Zoology (Vou. 18

lation of the middle area results in a constriction, due to the contrac-
tion of the circular muscles with no reflex to the longitudinal muscles.
In recovery from the ether treatment the longitudinal muscles recover
and reassume normal functions first and the circular some minutes
later. In creeping movements the middle section shows that the
longitudinal muscles recover their nervous connection first, for they
begin to contract in coordination with the anterior part, some time
before the circular muscles begin any active participation in the
general movement. This condition is due no doubt to the fact that
the longitudinal muscles le deeper than the circulars and so are less
affected by the anesthesia. In addition to this the position of the
longitudinal muscle is closer to the general blood supply, which would
be advantageous in the removal of waste products and the bringing
in of new materials.

THE PROBLEM

The problem then suggests itself: how is this transmission through
a number of segments accomplished? (1) Does Biedermann’s dis-
covery necessitate the existence of long fiber tracts in the cord? or,
(2) Can it be explained on present knowledge of the neurones? (3)
Are there any limits to the transmission through anesthetized areas?
(4) Can the speed of such impulses be measured, and how do they
compare with the speed of nerve impulses in other annelids?

ACKNOWLEDGMENTS

The greater part of the experimental work was done at Harvard
University during the year 1914-1915, under the general direction
of Dr. G. H. Parker, to whom I am greatly indebted for his very
kindly interest and his many suggestions. Later the work of bringing
together the results of the experimentation was done at the University
of California. I wish to acknowledge and express my appreciation
for the helpful criticism and advice of Dr. S. S. Maxwell, of the
Department of Physiology, and to Dr. C. A. Kofoid, of the Depart-
ment of Zoology, for the general supervision of the work and the
revision of this paper.

EXPERIMENTS WITH ETHERIZED WORMS
Problem.—Will it be possible to get transmission of locomotor
impulses through an anesthetized area in both directions, from anterior
to posterior and also from posterior to anterior?

1918] Bovard: Nervous Impulses in the Earthworm 109

Discussion.—lf a worm is etherized by the vial method and allowed
to creep on a damp surface, such as moist filter paper, it will be seen
to act like a normal worm in every way, except that the middle or
etherized portion takes no part in the contractions. With each pull
of the anterior piece it will stretch and passively contract as the pos-
terior piece moves up, without showing the normal waves of muscular
contraction seen in the active portions.

A worm, that is moving anteriorly, will reverse its direction and
creep posteriorly if stimulated on the anterior end. Stimulation of the
posterior end reverses the direction again. This indicates that nerve
impulses may pass up or down the nerve cord and that these impulses
may change the direction of the creeping movement, but it does not
indicate that the impulses responsible for the actual creeping pass
through the nerve bridge. There is still the fact that the muscles in
the etherized section attaching the anterior to the posterior part may
act as the ‘‘string’’ in Friedlander’s experiment and give the neces-
sary pull which keeps the two parts working in coordination.

Conclusion.—These simple experiments only show that there may
be transmission of locomotor impulses in both directions through the
nerve cord in an anesthetized region of the worm.

TENSION
(a) Experiments with Etherized Worms

Problem.—To what extent is the factor of tension or pull respon-
sible for normal locomotor reactions?

Method.—By the use of ether in anesthesia we are able to test out
the importance of the matter of tension or pull in the transmission of
locomotor impulses. It will be remembered that the etherized part
acts as one piece. No waves of contraction pass up or down this part.
A small piece of cork was glued to a glass plate and the glass plate
kept wet. A worm prepared by etherizing ten segments in the middle
portion was pinned to the cork so that the anterior and posterior parts
were free to move, but the middle part was fixed.

Discussion.—Under these conditions no movements of the anterior
part could exert any pull on the posterior piece. In all such experi-
ments the worms behaved as Biedermann (1904) reported, the pos-
terior piece responding with locomotor reactions in perfect codrdina-
tion to all attempts of the anterior piece to make creeping movements.
These movements could not be accomplished because of the shppery

110 University of California Publications in Zoology [Vou. 18

glass surface and the pinning down of the middle section, but the
wave of contraction, as in normal creeping, can be easily observed

(ig 1):

A B (S
Fig. 1. This shows the method of pinning the anesthetized region of the
worm. Region 4 has just made an anterior creeping movement and region C
can be seen making a codrdinated movement. On account of being pinned
through region B, the anterior part of C is forced to buckle.

The reversal of the direction of these movements is also possible.
Stimulation of the anterior end will cause the posterior end to attempt
ereeping posteriorly with the anterior piece acting in_ perfect
coordination.

If, now, the nerve cord be severed in the middle region without dis-
turbing the muscular connections a great deal, the coordinated move-
ments of the two ends cease and become independent each of the
other. It is possible when a worm is pinned and the continuity of
nerve in the anesthetized area is broken, that the anterior and pos-
terior ends may each be making locomotor movements in opposite
directions, showing an independence of action even though joined by
a muscular connection. There can be, therefore, no doubt that the
nerve cord earries, for some distance, impulses which are responsible
for locomotor movements. By pinning the worm to the cork, the
matter of tension has been eliminated and by cutting the nerve, the
transmission through the nerve cord has been removed and codrdinated
movements cease entirely.

When such a worm with transected nerve cord and anesthetized
middle section is released from its cork plate and allowed to creep
freely, it is found that the codrdination of anterior and posterior parts
is perfect. In this case, however, there is an entirely different
explanation. The codrdination of the posterior end can not be due to
any nerve impulses from the anterior end, but each forward move-
ment of the anterior section causes a pull on the posterior piece and
this starts a chain of reflexes at the anterior end of the posterior piece
which run the length of this part of the worm and give rise to the
muscular contractions which normally would give rise to locomotion.

1918 | Bovard: Nervous Impulses in the Earthworm IGE

In worms in which the entire dorsal wall, the lateral muscles, and
the intestine of the etherized part were dissected away and the nerve
cord freed from the ventral muscle by cutting the lateral roots, the
coordination continued perfect in function between the anterior and
posterior portions. It was observed that such specimens, in creeping,
did not move with the middle section tense, as a string connecting the
two parts, but that often the posterior part moved along rapidly,
causing the middle part to buckle so that under these circumstances
no pull could possibly have been exerted on the posterior part. When
the anterior part was pinned down, the posterior piece still continued
its coordinated movements and ‘‘telescoped’’ anteriorly into other
parts. .

Conclusion.—Tension or pull, while important in normal creeping
movements, may be eliminated and the locomotor stimulus will still
pass on down the nerve cord for some distance.

(b) Autotomy

In the course of administering the anesthesia to the middle portion

of the worms, it sometimes followed that the strong contractions

would break the muscular walls of the body, a condition of incomplete

autotomy. If the animal was released in time the anterior and pos-

terior ends would remain connected by the intestine and the nerve
cord (fig. 2).

Fig. 2. This shows the nervous bridge as made in an incompletely auto-
tomized worm. The break in the musculature occurs between the segments.
The intestine (int.), with the dorsal and ventral blood vessels (d.bl.v. and v.bl.v)
and a portion of the ventral nerve cord (n.), may be seen.

Problem.—Is the nervous bridge made by incomplete autotomy
between anterior and posterior ends of the worm capable of trans-
mitting locomotor impulses in both directions as in the etherized
worms ?

112 University of California Publications in Zoology [Vou. 18

Discussion.—Under these circumstances the reactions of the par-
tially autotomized worms are the same as in etherized ones; creeping
anteriorly and posteriorly can be induced by stimulation. If the
anterior end is pinned, the posterior part will still act in coordination ;
in this case the only possible way for the transmission to take place
would be through the nerve cord. Microscopical sections of such cases
as these showed that the nerve card was quite normal in structure and
still intact.

Friedlander (1894) laid such stress on the matter of tension, the
pull of one part on the next succeeding segment, that the behavior of
the worm under these conditions of anesthesia becomes particularly
important as bearing on the correctness and completeness of his
explanation (fig. 3).

Fig. 3. An illustration of Friedlinder’s experiment which shows the anterior
and posterior parts of the worm tied together with a thread. The movement
of the anterior piece pulls on the anterior end of the posterior piece and starts
the locomotor reactions which are codrdinated with those of the anterior half.

Conclusion.—In cases where the tension is eliminated by pinning
the worm to a cork on glass, the posterior part can be seen to begin
rhythmical movements of contraction codrdinated with those of the
anterior part. If this anesthetized portion is composed of but few
segments, then the codrdination is most perfect and the beginning of
the movement of the posterior section follows in shorter time than
when this portion of the worm includes many segments. It is possible
to anesthetize a section of such length that no coordination is carried
on and the posterior part lies entirely inert. In Helodrilus trans-
mission of impulses was effective through 20 segments, rarely through
28, and never through more than 30 segments.

NERVE FREE PREPARATIONS

Problem—The fact that the worms perform autotomy and that the
anterior and posterior parts are then connected with each other only
by a simple nerve bridge and the intestine, suggested the possibility of
dissecting away all the connecting muscle between the anterior and
posterior parts. Could the nerve cord be dissected free for a distance
exposing several ganglia and could locomotor impulses be transmitted
through such a cord?

1918] Bovard: Nervous Impulses in the Earthworm 118

Methods.—(a) Dissection. All the muscle in the anesthetized
region was cut away after the worm had been pinned to a cork plate.
Owing to the fragility of the nerve, it was easily broken and in cases
where it was not broken it was easily impaired by stretching, so that
particular care had to be taken with the preparations made. Here,
as in the experiments discussed above, where transmission was over a
few segments, the codrdination was good and as the nerve bridge was
lengthened the coordination was less complete and finally failed. Such

”’ effect on the animal and

an operation must have a decided ‘‘shock
it does not behave as would be expected under more normal conditions,
consequently the length of the nerve does not represent the limits of
transmission, as will be shown in some experiments to be discussed
later.

In all these cases it was necessary to keep the worm pinned, for if
allowed free creeping the anterior part would move more rapidly than
the posterior, the nerve was not strong enough to drag the weight of
the posterior part and so the nerve was promptly broken.

In my first dissections all of the musculature in the anesthetized
region was removed, so that the nerve cord was the only connection
between the anterior and posterior parts of the worm. Later I modified
this so that the nerve cord, while entirely free for several segments,
was not allowed to touch the cork plate but was kept in its own body
fluids on a piece of muscle (fig. 4). All the muscle on the dorsal and

Fig. 4. Type of dissection used in nerve free preparations. (n.) nerve cord
with lateral roots cut (l.7.), intestine (int.) and blood vessels (d.bl.v. and v.bl.v.)
cut away.

lateral walls was dissected off. The intestine was removed. This left
the nerve cord attached to the ventral plate of muscle. A sharp flat
stylet was introduced under the nerve cord and all the lateral roots
_severed. A transverse cut was then made across the ventral muscle
so that no muscular connection remained between the two parts of the
worm. When this type of operation was used much more uniform

114 University of California Publications in Zoology (Vou. 18

results were obtained than where the nerve was allowed to come in
contact with the cork of the dissecting tray. Garrey and Moore (1916)
used a method similar to the earlier method that I used with the same
general results.

(b) Graphic Records. Apparatus. As a check on the observations
just described, it became desirable to find some way in which to make
a graphic record showing the part the nerve cord plays in the trans-
mission of locomotor impulses. The movements of the anterior and
posterior ends of the worm, while the middle part was fixed to a cork
plate glued on glass, suggested that if levers were attached to these
moving parts a record could be obtained on a kymograph. It was
necessary in order to obtain good records to have the levers as light
as possible and to have them move with very little friction. This was
accomplished by making the levers of aluminum wire, number 22. A
desired length was inserted in a cube of cork. Through the cork a
small glass capillary tube was thrust which made the bearing for the
axle of the lever. A very fine needle was then fitted into the glass
capillary and the needle stuck into a firm support. This sort of a
bearing allowed the lever to move with little friction and also was

Fig. 5. The general arrangement of the apparatus for recording movements
of the anterior and posterior parts of the worms. Method used at Harvard,
1914-1915.

a.l.—Aluminum wire lever connected to anterior end of worm by hook and
thread; ¢.—Cork plate glued to glass for pinning the middle anesthetized por-
tion; ¢.c.—Cork eubes through which aluminum wires run; g.pl.—Glass plate to
which a little water was added to allow the worm to slide back and forth when
pinned; p.l.—Aluminum wire lever connected to posterior end of worm by hook
and thread; ky.—Drum of kymograph for taking tracings on smoked paper;
wt.—Counter balance weights.

1918 | Bovard: Nervous Impulses in the Earthworm 115

advantageous in that it allowed little side lash. Various forms of
levers could be built up by means of extra cork cubes and short sections
of aluminum wire, as in figure 5, a.l. and p.l.

The levers had to be weighted slightly so that the worm would be
kept in a straight line on the glass plate or else the curves recorded
would be exceedingly irregular (fig. 5).

If now a worm is prepared with the middle part anesthetized and
arranged to record movements, the movements of the posterior part
should show a perfect codrdination with those of the anterior part
(fig. 6).

Fig. 6. Experiment 143. <A record showing perfect coordination between
anterior and posterior parts with a middle area of eight segments anesthetized
and musculature cut away. The upper curve represents the movements of the
anterior end and the lower that of the posterior end. Transmission of impulses
mediated through the nerve cord only.

The method of preparation of the middle portion varied. In some
cases the worm was treated with ether by the vial method, and then
triple-pinned to the cork plate. In other cases, in addition, the dorsal
musculature was cut away, the intestine removed, exposing the nerve
cord, and the lateral branches of the nerve cord transected. In still
other cases the musculature was cut in the middle region but not

116 University of California Publications in Zoology (VoL. 18

removed; so the nerve could rest on its own body fluids. In all these
cases coordinated movements of anterior and posterior portions were
shown. The best records were obtained when the least dissection was
used.

The clinching argument, however, was obtained when during the
course of such experiments the nerve cord is cut. In all such cases, no
matter what type of dissection was used, non-coordinated movements
were shown when the cord was transected (fig. 7).

Fig. 7. Experiment 143. Explanation of the curves here the same as in
figure 6. The nerve cord connection between anterior and posterior has been
cut. Notice the lack of codrdination between the movements of two portions
of the worm.

(c) Stovaine. Should any doubts still remain concerning trans-
mission of impulses for locomotor movements over long sections of the
nerve cord, the action of stovaine will set these completely at rest. If
stovaine be injected into the body cavity of the worm it acts as a block
to the nerve cord over four or five segments and allows no impulses to
pass up or down through the segments containing the anesthetic. The
records will show that there is a lack of codrdination and suppression
of movements of the posterior end while the drug is effective (fig. 8),

1918] Bovard: Nervous Impulses in the Earthworm LG

24] 250

post.

meh

a eS Ne
A B

Numbers refer to time of day animals were tested.
Arrow indicates stimulus given to the anterior end.

Fig. 8. Experiment 190. Stovaine injected into middle section of worm,
four segments affected. Lower curve registers the movements of anterior end
and upper curve those of the posterior end. At 2:41 p.m. the codrdination
between anterior and posterior parts is not normal, and at 2:50 P.M. the giant
fiber action is lost. Stimulation at the arrow fails to give a reaction in the
posterior part.

A represents ordinary locomotor activities.
B represents giant fiber action.

but as soon as the effects begin to wear off, the coordination between
the two parts becomes more and more complete until finally the
anterior and posterior parts are again acting in perfect rhythm (fig. 9).
The supposition in this case is that stovaine acts on tissue of earth-
worm as it does in the vertebrates, where it has no effect on muscle or
nerve endings but acts only as a ‘‘block’’ on nerve fibers. The effects
of the drug were kept localized to small sections while anteriorly and
posteriorly all the normal reactions could be obtained.
Conclusion.—The nerve-free preparations, the graphic records of
movements before and after the nerve was cut, and the physiological
block established by stovaine, all go to show that the locomotor impulses
travel considerable distances in the cord. This work confirms the
results obtained by Biedermann but by quite different methods. The
most important aspect of these results is the demonstration that

118 University of California Publications in Zoology [Vou.18

locomotor impulses are not ‘‘short relays’’ depending on a stimulus
from each segment, but are capable of running a number of segments
with no stimulus from the outside.

620
post.
i
1
i]
'
{
I
t
time in
/ ; 1/5 sec.
| t
‘
i]
4
'
'
{
'
t
t
ant.

A B
Fig. 9. Experiment 190. Continuation of experiment shown in figure 8. At
6:20 p.m. the worm had recovered from the effects of the stovaine. Normal
coordinated movements are being made (A) and the giant fiber action has
returned (B). Stimulation of the anterior end at the arrow shows a response
in the posterior end.

Limits oF TRANSMISSION

Problem—How far will these locomotor impulses travel in the
cord? Can a middle area of sufficient length be anesthetized so that
no impulses from the anterior piece can get through to start locomotion
in the posterior part?

Discussion.—It was soon discovered that transmission was_ best
shown when it was concerned with few segments and that, as the
number of ganglia through which the impulse must pass was increased,
the coordination became less and less perfect. No sharp limits could
be determined. When the nerve cord was dissected free from muscle,
the most severe type of dissection, the transmission seemed to be
limited to eight free ganglia. In one case, codrdinated movements
were obtained when ten ganglia had been freed, but this was unique.

1918 | Bovard: Nervous Impulses in the Earthworm 119

When the length of the free nerve contained four ganglia, transmission
was easily demonstrated.

In those cases where the dissection included the removal of the
dorsal wall, intestine, and the transection of lateral nerves, the trans-
mission easily ran for more than ten segments, but never for more
than twenty-eight.

It has been demonstrated by Biedermann (1904) and confirmed by
my own experiments, that the impulses run long distances in the cord
when the worms are anesthetized in the middle region which is after-
wards treated with six per cent nitric acid. In such cases, records of
transmission were obtained when twenty segments intervened between
the still active anterior and posterior ends. Failures came more often
as the leneth of this etherized part was increased. One record was
obtained with the large Helodrilus where codrdinationed movements
appeared in the posterior part when twenty-eight segments were
etherized and their muscles killed with nitric acid.

These results fall somewhat short of the cases reported by Bieder-
mann, where coordinated movements were obtained through anes-
thetized parts two to three centimeters long, but the number of seg-
ments is not stated. The greater part of my records were obtained on
Helodrilus, where twenty segments of the body, in the part measured,
approximated two centimeters. While this does not show a great dis-
crepancy, my results are apparently nearer the lower figure quoted by
Biedermann.

We can establish, then, no absolute limits, except to say that trans-
mission is fairly well accomplished over ten segments, may run to
twenty and even to twenty-eight, but that the longer the nervous
bridge the greater the difficulty. No records have been obtained where
thirty segments were concerned.

One factor which makes the determination of any such records
very difficult is that impulses from normal stimuli in normal worms
starting down the length of the worm do not necessarily continue to
the end. The dying out of an impulse is quite a usual phenomenon
seen in the contraction waves that run only part way down the animal.
One of these impulses may start into the cord of the etherized part
and never reach the other end of the etherized part of the worm. This
does not mean that no impulses can come through, and so no limit can
be determined by this failure, but it does indicate a dying out of this
particular impulse somewhere in transit. Therefore, in the experl-
mental determination of the limits to transmission, as long as impulses

120 University of California Publications in Zoology [Vou 18

come through the etherized part we are still within the limits of trans-
mission, but as soon as failures become frequent it is evident that the
limits have been approached. More refined methods may be able to
determine these limits closely. My records can be considered only as
approximations.

One other difficulty arises in making these determinations. Sum- .
mation of stimuli has been shown by both Straub (1900) and Buding-
ton (1902)-for annelid muscle. Weak stimuli adding themselves
together will sooner or later give a contraction. There is the possi-
bility that, in observations on these reactions, failures have been
recorded, where, in reality, weak stimuli did get through. However,
any errors so made would be on the conservative side.

Conclusions.—The results of these experiments show that no
absolute limits ean be set, the impulses travel short distances in the
cord very readily and that the longer the section of cord to be traversed
the greater the difficulty. In Helodrilus twenty-eight segments was
the limit for the distance locomotor impulses would travel in the cord
when the superficial nerves were anesthetized.

DEPENDENCE ON NERVOUS SYSTEM FOR TRANSMISSION

Problem.—While the nerve cord is capable of transmitting loco-
motor impulses for considerable distances is it possible for the muscles
to carry on rhythmical movements without the aid of the nervous
system ?

Discussion.—lf a short section of a worm containing about twenty
to thirty segments is prepared in such a way that it will give a record
of contractions of the longitudinal muscles on a moving drum, and the
lever is slightly weighted so the piece will be kept straight but not
stretched, it will be found to make rhythmic contractions. Straub
(1900) and Budington (1902) show this characteristic of annelid
muscle but disagree in the interpretation. Straub claims that strips
of the muscles, both with and without nerve, will give rhythmic contrac-
tions. However, regions of the worm from which the nerve had been
removed must be given several (eight) days for recuperation and then
they would give contractions comparable to those of the regions of
worm with nerve intact. Budington found that when care was used
to remove all nervous tissue by using only pieces of worm in which
the whole ventral muscle had been removed, that such pieces gave no
rhythm ; while pieces containing even a small amount of nerve gave a
regular rhythmic curve (fig. 10).

1918] Bovard: Nervous Impulses in the Earthworm 121

A = Short piece of whole worm with nerve cord.
B = Dorsal longitudinal half without nerve cord.
C = Ventral longitudinal half with nerve cord.

Fig. 10. Experiment 104. Curve A is made by a short piece of worm
attached to a writing lever. The piece was normal in every way and gave
rhythmical contractions. Curve B represents a curve made by the dorsal half
of a short piece of a worm that had been split in two longitudinally. This
piece contained no nerve cord. Curve C was made by the ventral half of a
short piece of a worm that had been split in two longitudinally. This piece
did contain the ventral nerve cord and did give rhythmic contractions.

My results agree entirely with those of Budington. It is quite
possible that the findings of Straub may be due to a factor that he
overlooked, the matter of regeneration. As I shall show in a later
paper, regeneration is exceedingly rapid and there is a possibility that
nerves have grown into the operated portion, and the probability is
that Straub was really dealing with pieces in which nerve fibers and
cells had regenerated.

As further evidence of this dependence upon the nerve cord for
transmission it will be noted that when a worm is pinned in the middle
portion to a cork plate and the anterior and posterior ends are regis-
tering coordinated movements on a revolving drum, if the nerve be
cut in the pinned region the rates of contraction of the two parts will
be immediately changed. In this case, the muscle is disturbed as little
as possible and only the nerve cord is cut (fig. 11).

Read in this direction —>

Fig. 11. Shows how the posterior half of the worm changed its rhythm after
the nerve cord had been cut. The upper line represents the movements of the
anterior (4) half and the lower line the posterior (B) half. The nerve cord
was cut without cutting any but a small portion of the ventral muscle.

Conclusion—From the work just cited, it is quite certain that
spontaneous movements are dependent on the nervous tissue and that

122 University of California Publications in Zoology [Vou.18

the muscle has no property of rhythmie contractility. While this does
not show that transmission of impulse passes over many ganglia in
locomotion it strengthens the work of Biedermann (1904) and Bud-
ington (1902) who hold the theory of nervous control.

RATES OF TRANSMISSION OF LOCOMOTOR IMPULSES

Problem.—The fact that locomotor impulses could be transmitted
through a portion of the nerve cord isolated from segmental muscle
connections led to the query, what is the speed of these impulses? If
the speed were rapid it would mean that there were some fairly long
neurones in the cord, and if the speed were slow it could be interpreted
on the basis of short neurones and many synapses. This study should
throw some light on the structural basis of transmission.

Discussion—Jenkins and Carlson (1903) measured the rate of
nerve impulses in several species of annelids. The rates were found
to be exceedingly variable, from 89 centimeters in Nereis sp. to 694
centimeters per second in Bispira polymorpha. The question these
investigators raised was whether they were dealing with simple con-
tinuous nerve fibers or with a very complex nervous tract. While the
anatomical connections of neurones in the cord have been worked out
to some fair degree of certainty, no long connections have been estab-
lished in the cord, except by the giant fibers. Jenkins and Carlson
left the question open as to whether their measurements were those of
a direct nervous path or an indirect one.

After observing a very large number of experiments on the trans-
mission of the impulses as they pass through the etherized section of the
worm, and noting the slow progress of these as compared to the quick
end to end jerk of the worm when stimulated, there is lttle doubt
in my own mind but that the cord has two kinds of transmission of
nerve impulses. First, the very rapid impulses through giant fibers,
which result in vigorous contractions, as in the jerking back into their
burrows of the worms when strongly stimulated; and the second type,
the impulses in the short fibers in the middle of the nerve cord, which
offer a complex path and so transmit impulses slowly down the cord.

My records for the speed of impulses in the giant fibers agree quite
well with the speed recorded by Jenkins and Carlson (1903). The
method which these workers used was such that only the action of
quick contractions was recorded and no attempt was made to separate
this phenomenon from that of the locomotor impulses. As has been
shown, these latter impulses run but short distances in the cord unless

1918] Bovard: Nervous Impulses in the Earthworm 123

reinforced by outside reflexes; and so, unless special methods are used,
the reactions of these short fiber systems would not be observed.

A frequent observation on the locomotor habits of worms is that
the wave of contraction runs for a short distance and then disappears.
This was a source of great inconvenience in determining the rate of
impulse down the cord. A method was devised whereby electric con-
tacts were successively made as the wave of contraction passed along
the worm. These were recorded on a drum from which measurements
were easily made and speeds computed (fig. 12).

fee oerast

ant. x. Cc. pl. post

Fig. 12. The apparatus for measuring the speed of nervous impulses through
the nerve cord in an anesthetized region was as follows: a.l. and p.l. are levers
pivoted at piv. The lower part of the lever n is a sharp, very fine needle. One
of these is thrust into the muscles of the first segment in front of the anesthet-
ized part m. and the other into the muscles just behind this region m. The
upper ends of these levers is quite long so that very slight movements of the
lower part will produce considerable movement in the upper part. Platinum
contacts were provided at pt.c. and each lever was connected by battery to
signal magnets, a.s. and p.s., which gave a record on a smoked drum of a
kymograph. When the locomotor movement of the anterior part of the worm
had reached the muscles at x. the electrical contact would be made in lever a.l.,
which registered on a fast revolving drum at a.s. Now when the nervous impulses
had passed through the anesthetized area m. and reached the muscle y. another
electrical contact was made by lever p.l. and registered by signal magnet p.s.
The speed of the drum being measured, the speed of the impulse could be
ealeulated.

124 Umwersity of California Publications in Zoology [Vou.18

The very noticeable result of this series of experiments was the
great variability in the speed, which seemed to depend on the state of
irritability in the worm.

Another important fact seemed evident from these measurements ;
namely, the longer the section of nerve measured the slower the rate
recorded.

TIME TAKEN TO TRAVEL OVER CERTAIN LENGTHS OF NORMAL AND
ANESTHETIZED WORMS

EXPERIMENT 180 EXPERIMENT 162 EXPERIMENT 162
13 live, 20 etherized 11 live, 20 etherized 19 live, 20 etherized
segments segments segments
1 .26 seconds .90 seconds .68 seconds
2 44 50 .65
3 .24 .64 70
4 eal .60 90
5 20 .o4 70
6 30 4 82
7 1.02 30 92
8 2 20 75
9 SII) 40 Se
10 .08 25 72
Average 370 452 .760

1 These figures are calculated from experiment 180, a series different from
that in columns 2 and 3.

The method for making these records was not refined and the
times recorded can only be approximations. The table will show that
where the length of the portion of the worm measured is increased the
time of transmission increases, but not proportionately. The full
significance of this fact and its relation to transmission and a new
theory of locomotion will be brought out in a later part of this paper.

In measuring the speed of the impulse through the nerve cord in
a section where the muscle had been anesthetized, the electric method
of measurement was quite effective. Records of slight movements of
the segments just anterior to the inert section were followed by the
registration of movements beginning in the part immediately behind
this portion. Here again we meet great variability, depending on the
state of excitement in the worm. If the etherized section is greatly
increased in length the point will eventually be reached when no
impulse comes through. Records through more than twenty segments
were frequent, but when more than twenty segments were used, failure
resulted more often than in fewer than twenty. Measurements were
recorded over twenty-eight segments but these seemed to be exceptional

1918 | Bovard: Nervous Impulses in the Earthworm 125

eases. For the most part, impulses passed along the cord at the rate
of about 25 millimeters per second. This represents the mode of a
series of ninety-one measurements. Several observations showed good
transmission at the rate of 60 millimeters per second, and a few were
recorded in which the rate was very low, 10 millimeters per second
(fig. 13).

20

Aouanbes4
i)

o

0 10 20 30 40 50 60 70 80 90 iteje) i}te)

Fig. 13. The frequency polygon which shows results of ninety-one measure-
ments of the speed of locomotor impulses through the nerve cord when the
peripheral nerves have been anesthetized. The mode lies between 20 and 30
millimeters per second.

Conclusion.—The locomotor impulses show no definite speed. The
most interesting feature is the extreme variability of this movement.
In those cases where strength of stimulus is sufficient and other con-
ditions are right the speed may be as fast as 100 millimeters per
second, and again the speed may be so slow that it will die out in the
nerve cord without ever emerging from the anesthetized region. I
have taken the mode of the frequency polygon as against the average
which shows that ordinarily the speed is about 25 millimeters per
second. The slowness and variableness are the two main character-
istics.

RATE OF IMPULSES IN THE GIANT FIBERS

Problem.—How does the rate of transmission of locomotor impulses
compare with that of the giant fiber? Are the rates such that these
two phenomena can be ascribed to quite different systems of neurones?

Discussion.—The method used to measure the rate of transmission
of impulses in the giant fibers was practically the same as that used
in measuring locomotor transmission, except that in this case it was

126 Unversity of Califorma Publications in Zoology (Vou. 18

possible to use the full length of the worm. One characteristic of this
type of action is that it seems to be related solely to the longitudinal
muscles in contrast to that of the locomotor nerve fibers which set up
complex reactions in both circular and longitudinal muscles.

Responses resulting from stimulation of these large fibers are always
exceedingly rapid as compared with other movements of the worms.
The reaction may be slight or violent, according to the amount of
stimulus applied, but any response travels the length of the worm in
a very short time. It is interesting to note the antagonistic relations
of the innervation of muscles when a quiescent worm is stimulated
lightly, with a sharp needle, at the anterior end; immediately there is
a response by a relaxation of the circular muscles near the posterior
tip so that this part is flattened and enlarged. If the stimulus is made
stronger, this reaction will be followed by a jerk of the longitudinal
muscle and when the stimulus is moderately strong the contraction of
the longitudinal muscle is so quick and extensive that no reactions
of the circular muscle can be detected.

A number of determinations for speed of this rapid action are
recorded in the accompanying table. The range of variation is large,
due in part at least to the methods of measurement and the inaceur-
acies of the apparatus (fig. 14).

° 500 1000 1500 2000 2500 3000 3500 4000 4500

Fig. 14. Frequency polygon which shows the speed of impulse through giant
fibers. The figures represent millimeters per second. The mode is between 1000
and 1500 millimeters per second.

All of these measurements were made on the large garden worm,
Helodrilus caliginosa, and as nearly as possible under the same con-
ditions. The interesting feature of this array of figures is that they
are high compared to those obtained in locomotor transmission. Ordin-
arily they can be said to be fifty times faster, and may even be one
hundred times faster, than the other type of transmission. The
mode for these few measurements is around 1500 millimeters per
second. While this is not so rapid as some recorded by Carlson and
Jenkins (1903) (table 1), in measurements on marine annelids, it is
certain that it belongs in the same class of phenomena as they were

1918 | Bovard: Nervous Impulses in the Earthworm 127

TABLE 1
SUMMARY OF RATES IN WORMS—CARLSON AND JENKINS
Species Direction Centimeters per sec.

Were oma al us peeesrn eee cere iP A 5.4— 9.0
Aulastoma lacustre .................. 12 A 56.0
(Ojrreez i HOUNDS) FS} OS oes eee iP A 90.0
ANTAGINGONGY, (SOY, ~ cdeceaecssereeee eee A 12 120.0
Bispira polymorpha ................ 12 A 694.0
PACT OCICO Se cer eacc 38-2 acct secs ice A Ie 54.0
ZOlymoen pul Clima; eee eee IP A 293.0
Sihenelarsieus cays eee ee 12 A 205.0
HET UTG CES spent eee eee 1 A 466.0
INGA SINS) OF cece toes ee ee ee 12 A 165.0
INererstiavamenigt 2 2 4e oe 12: A 89.0
ING GETS eva CMS ee eeenee eee : A 12 73.0
Lumbriconereis sp. (@) -......-... 12: A 45-241.0
Lumbriconereis sp. (0) .....-....-- 12 A 49—-937.0
umibriconeneisispe (Ge) see A IE 42—-160.0
GHB VOGIE), TRBEKOSE), ssc caqs- coer cere A ‘iP 433.0
Civceraeni gO Sages creas 1 A 435.0

measuring. None of my measurements approached the highest speeds
in these marine forms, such as that in Bispira polymorpha, viz., 6940
millimeters per second, or even in Lumbriconereis sp., viz., 9370 milli-
meters per second, nor on the other hand did I find any as slow as
that in Cerebratulus at 54 to 90 millimeters. Several worms, Nereis,
Arenicola, Sthenelais, give averages about the same as that which I
found for Helodrilus.

Jenkins and Carlson used averages in obtaining the figures above,
when it would seem such a variation in measurements occurred that
the mode is more nearly the correct expression. I have used this in
both series, that on locomotor transmission and on giant fiber action.

One feature of giant fiber action that is easily noticed is, that,
once started, it always goes through to the posterior end; it never dies
out in transit as the locomotor waves do. In cases where the nerve
cord has been severed, the impulse runs as far as the cut, and never
beyond.

Krawany (1905) in his discussion of the elements in the central
nerve cord describes the relations of the giant fibers to the association
cells in the cord. These large fibers pass from end to end of the nerve
cord and in each ganglion send out branches which are intimately in
connection with processes from association cells in the middle group.
These cells which thus synapse with the direct fibers never have cross-
over connections but seem to be entirely homolateral.

128 Umversity of California Publications in Zoology [Vou.18

The physiology of these reactions is correlated with the anatomy
of these fibers. The path is a direct one and the speed of their
impulses is fast, 1500 millimeters per second compared with 25 milli-
meters per second for locomotor reflexes. The connections are simple
and the reactions are concerned largely with the contractions of but
one set of muscles, the longitudinal muscles. The fibers run the full
length of the cord and so reactions are concerned with the whole
animal. They are single fibers and produce a single action. There
is no wave motion nor evidences of loss as the stimulus passes down
the cord.

There is no reason to suppose that these fibers have anything to do
with locomotor reflexes or transmission ; everything points to a separate
function for these large long fibers.

Conclusion.—We have taken for granted that Friedlander’s (1894)
suggestion that the end to end movements are due to impulses carried
by the giant fibers. The results of this work on rates of transmission
seem to justify this supposition. No theory allows a nerve to have for
itself more than one rate of transmission. The speed of one type of
action and the slowness of the other would necessitate two kinds of
fibers. The anatomical conditions and the physiological reaction are
easily correlated. The large giant fibers are continuous structures
running the full length of the worm and capable of carrying the
impulses swiftly from end to end at a normal rate of 1500 millimeters
per second, while in the center of the nerve cord are numerous short
neurones running short distances up and down the cord, giving a
complex path, with slow speed of transmission, normally 25 mill-
meters per second, such as would be expected on account of the
multiplicity of synapses.

THEORETICAL CONSIDERATIONS

The Nervous Mechanism.—Some of the most salient facts brought
out in the study of transmission are: the nervous system plays an
essential part in the movements of locomotion; the impulses respon-
sible for the waves of contraction are capable of running for con-
siderable distances in the cord and are not confined to one or two
segments, as indicated by Friedlander; transmission may extend over
as many as twenty segments without intervening muscular activity,
the rate of transmission is a variable one becoming slower as it pro-

ee eee a ee ee

1918] Bovard: Nervous Impulses in the Earthworm 129

ceeds. The giant fibers have little to do with locomotion and are
specialized for rapid, end to end contractions.

The excellent work of Krawany (1905) on the neurones of the
central system of the worm and the researches of Dechant (1906) on
the peripheral nervous system, together with the great amount of
work done by the older writers, such as Bethe (1903), Rhode (1887),
Apathy (1897), Retzius (1900), Biedermann (1904), Smirnow (1894),
and others, have demonstrated that the nervous system is compounded
of many short neurones. The longest elements are some few large
fibers from the anterior end of the cord which arise in the sub-
esophageal ganglion and run posteriorly to the terminal segment, but
Krawany (1905) shows that for the most part the other nerve fibers
run only from one ganglion to the next.

Sensory nerve fibers originating in the epidermis pass down
through the main nerve trunks to the ganglion where they branch as
T- or Y-shaped bifurcations immediately on entering. These run but
short distances before ending in fine arborizations. Krawany (1905)
was unable to demonstrate that these passed into ganglia anterior or
posterior to the segments of entrance, but was inclined to think that
they remained within the ganglion entered. No demonstration of
neuro-muscular end organs has ever been made in the smooth muscle
of earthworms. Retzius (1895) and Langdon (1900) have shown, by
using Golgi methods, that nerve fibers are in among the muscle cells,
but Dechant (1906) by using methylene blue was unable to differ-
entiate any definite end organs. Many nerve fibers parallel to muscle
can be seen, showing the presence of abundant nervous tissue, but all
fibers which looked like end organs proved to run only short distances
and could not therefore be true nerves. While free sensory endings
in the subepithelial regions are not yet demonstrated, Dechant believes
they are undoubtedly there.

After entering the cord the sensory nerves bifurcate, one branch
passing up and another down the cord on the same side as they enter.
They may then form synapses with neurones of motor ganglia in the
anterior, middle, or posterior groups of nerve cells. These large cells
send out neuraxes which may or may not cross to the opposite side,
where they leave by one of the three lateral roots.

Within the cord, however, there are still other paths open to
impulses entering by the sensory paths. The large multipolar cells are
the association cells which show an arrangement into three groups, an
anterior, a middle, and a posterior group. Their function is to connect

130 University of Califorma Publications in Zoology Vou. 18

more or less distant parts of the ganghon and to interpolate them-
selves between the sensory and motor elements. Many of these are
homolateral and some are contralateral. The greater number of these
association cells are intraganglionie, i.e., never leaving the segment;
but a few in the anterior and posterior groups send processes into the
next ganglion and so connect up the ganglia segment to segment.

The most interesting feature is that in this nervous system there
are no long nerve tracts, the giant fibers excepted. IJImpulses that
run the length of the cord must find their way over a complex route
and be necessarily slow. We have then a nervous system made up of
many short units. Each ganglion is a complete relay station capable
of receiving sensory and giving out the motor impulses necessary for
the functions of each particular segment. The only connections
between the succeeding segments are association fibers in the nerve
cord and a few motor fibers which Dechant (1906) shows. These
motor fibers take their origin from a nerve arising from the posterior
root and pass laterally around the muscular wall near the interseg-
mental furrow and at intervals give off five branches which pass into
the segment behind. Without these two connections, one in the cord
and one peripheral, there would be no nervous connection from seg-
ment to segment of the worm.

Friedlander (1894) laid particular emphasis on the ‘‘pull’’ of one
segment on the succeeding ones and that codrdination was accom-
plished even though the nerve cord were cut. The experiment of
eutting a worm in two and attaching a string to each part resulting
in coordinated movements indicates that pull certainly does play an
important part. Undoubtedly the tension or stretching stimulates
the nerve and starts the reflex movement. The succeeding movements
then are due to both pull and nerve impulse. If part is etherized, it
ceases contractions although it responds to direct stimulus. The nerve
reflex has been broken. Again, if tension be eliminated by pinning
experiments, codrdinated movement proceeds; but if now the nerve be
eut, coordination ceases. So while tension is important in supplying
a stimulus to the nerve mechanism, it is not wholly sufficient.

Biedermann (1904) showed that these reflexes can travel consider-
able distances in the cord. The interpretation of this might demand
that there be present in the nerve cord longer systems of neurones
than had been previously reported. However, it can be shown that
no such supposition is necessary. The present knowledge of the
neurones can be used to explain the facts at hand.

1918] Bovard: Nervous Impulses in the Earthworm 131

TRANSMISSION BY REINFORCED STIMULI

There is one other point of great importance in the analysis of
locomotion in the earthworms and one which has not been heretofore
mentioned. This is the variability in the rate of the impulse along
the cord. Experiments have shown that the transmissions over short .
distances are much faster than those over longer distances, and this
agrees with a phenomenon easily observable in the movements of
worms, 1.e., the dying out of waves of contraction. One ean watch a
wave of contraction start down the length of the worm and become
more and more feeble until it is lost at the middle region. The distance
the wave runs seems to depend on the force of the wave at the start.
A strong wave runs further than one with a weak start. A glance back
at the charts of the speeds of impulses passing through the etherized
portion of a worm will show that there is a great variability. One
has but to observe a smgle worm under the experimental conditions
to become convinced of this without the figures.

Any theory that accounts for locomotion must take into considera-
tion the short unit system of the nervous system, the transmission of
locomotor impulses over long sections of the cord, and the variability
in rate of the speed of these impulses.

Friendlander (1894) likened the locomotor mechanism to a system
of telegraphic relays. Each contraction of the circular muscle elongated
the segment and stretched the longitudinal muscle. This stretching
caused a stimulus to pass along the nerves to the cord, where a reflex
gave a contraction of the longitudinal muscle. The contraction of the
longitudinal gave the pull which caused the circular muscle to contract
and so on down the length of the worm, each segment with its own
reflex, but progression of the wave of contraction due to the pull of
contracting parts on succeeding segments.

A short unit nervous system is all that is necessary for such an
explanation. But when transmission of locomotor impulses can pass
along the cord this relay system in each segment is not sufficient. If,
however, we suppose that the association fibers transfer stimuli from
one ganglion to the next, then we have a means for explaining Bieder-
mann’s experiment. One of the characteristics of this transmission
was that it varied considerably in rate. When the worm was in an
excited state or stimulated, the impulses passed through an etherized
section faster than otherwise. If we suppose that with each contrac-
tion reflexes are set up in each segment and that these stimuli entering
the cord reinforce the locomotor stimuli passing along in the short

132 University of California Publications in Zoology ([Vou.18

association tracts, and that if these stimuli are heavy they add to the
strength of stimulus passing along, or if weak add little or nothing at
all, then we have a basis for explaining the variations in rate. In
each ganglion there will be at least one and maybe two synapses to be
passed, each with a certain resistance which will tend to cut down the
force of the stimulus and its power to get through. Each synapse in
each segment resists the passage of the locomotor impulse but in
ordinary locomotion each well codrdinated contraction wave reinforces
the loss and the movement runs the full length of the worm. The
uncertain limit of such transmission then can be understood for many
factors may come in to change the force of the stimulus; the stimulus
may have started in a weak contraction—outside conditions may have
altered the amount of reinforeement—internal conditions in the cord
itself may have demanded a more complex path in one case than in
another, or even the physiological condition of the worm may have had
some effect on the resistance in the synapses.

SUMMARY

1. When a worm is anesthetized in the middle area and the peri-
pheral nerves are rendered useless, locomotor impulses may be trans-
mitted in both directions through the nerve cord of this middle region
from anterior to posterior, and posterior to anterior.

2. Tension or pull, while important in normal creeping movements,
may be eliminated and the locomotor stimuli will still pass up and
down the cord for some distance.

3. Nerve free preparations show that locomotor impulses may
travel considerable distances in the cord. Under such conditions the
anterior and posterior parts act in perfect codrdination. When the
nerve is cut such coordination ceases. Stovaine when applied to the
nerve cord blocks the passage of locomotor impulses up and down and
the codrdination of anterior and posterior parts is lost; as soon, how-
ever, as the effects of the drug are removed impulses again pass freely
in the cord and coordination returns.

4. The results of measuring the limits of transmission of the loco-
motor impulses shows that no absolute limits ean be set. The impulses
travel short distances of ten segments very readily but when required
to traverse a longer section of twenty-eight segments the difficulty is
great. No records show impulses passing through as many as thirty
segments.

Ve

1918 | Bovard: Nervous Impulses in the Earthworm 133

5. Spontaneous rhythmical movements are dependent on the
nervous system and the muscle tissues do not possess the property of
rhythmic contractility. This strengthens the theory that locomotion
is under nervous control.

6. The speed of locomotor impulses is quite variable. The mode
that expresses the normal rate is about 25 millimeters per second. The
rate may be increased or decreased in transit from segment to segment.

7. The rate of the transmission of giant fiber action is very rapid
when compared to that of the locomotor impulses. The mode for a
number of measurements shows the speed to be about the rate of 1500
millimeters per second. The wide gap between these two types of
nervous activity, the slow locomotor on the one hand and the rapid
giant fiber action on the other, indicates that these impulses are
mediated by two quite different kinds of nerve elements.

8. The anatomy of the nerve cord as shown by Krawany and
Deschant has in it no long neurones. The processes may join suc-
cessive ganglia but none extend through the cord for a great distance
except the larger giant fibers, which run the full length of the cord.

9. The peculiarities of the locomotor impulses in transmission, such
as the variability in rate of speed, and the slowness of it, can be
accounted for on the basis of the structure. The impulse to make its
way down the cord must pass in each ganglion at least one synapse,
and the possibility is that there would be more than this. Hach synapse
would not only cut down the strength of the impulse but would also
slow down the speed because of the time consumed to cross the gap
between neurones. In normal creeping the impulses travel regu-
larly down the cord because each contraction of circular and longi-
tudinal muscle in each segment sends in locomotor impulses which
reinforce the impulse passing down the central nerve cord, and any
loss through the synapse is made up in this way. If for any reason
the muscular activity fail or if the nervous connections to the cord be
destroyed the locomotor impulse traveling down the cord in this region
would decrease in strength and decrease in rate because of the lack of
reinforcement.

134 University of California Publications in Zoology [Vou. 18

LITERATURE CITED
APATHY, S.

1897. Das leitende Element des Nervensystems und seine topographischen
Beziehungen zu den Zellen. Mitth. Zool. Stat. Neapel, 12, 495-748,
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BeTHE, A.

1903. Allgemeine Anatomie und Physiologie des Nervensystems (Leipzig,

Thieme), vii, 487, 2 pls., 95 figures in text.
BIEDERMANN, W.

1904. Studien zur vergleichenden Physiologie der peristaltischen Bewegun-
gen der Wiirmer und der Tonus glatter Muskeln. Arch. gesam.
Physiol., 102, 475-542, 1 figure in text.

BUDINGTON, R. A.
1902. Some physiological characteristics of annelid muscles. Am. J. Physiol.,
7, 155-179, 16 figures in text.
DECHANT, E.

1906. Beitrage zur Kenntnis des peripheren Nervensystems des Regen-
wurms. Arb. Zool. Inst. Wien, 16, 361-382, pls. 1-2, 2 figures in
text.

FRIEDLANDER, B.

1894. Beitrige zur Physiologie des Centralnervensystems und des Bewe-
gungsmechanismus der Regenwiirmer. Arch. gesam. Physiol., 58,
168-206.

GARREY, W. HE. AND Moors, A. R.

1915. Peristalsis and codrdination in the earthworm. Am. J. Physiol., 39,

139-148, 2 figures in text.
JENKINS, O. P. AND CaRLson, A. J.

1903. The rate of the nervous impulse in the ventral nerve cord of certain

worms. J. Comp. Neur., 13, 259-289, 14 figures in text.
KRAWANY, J.

1905. Untersuchungen iiber das Zentralnervensystem des Regenwurms. Arb.

Zool. Inst. Wien, 15, 281-316, pls. 1-15, 11 figures in text.
KRUKENBERG, C. F. W.

1881. Vergleichend-toxicologische Untersuchungen als experimentelle Grund-
lage fiir eine Nerven- und Muskelphysiologie der Evertebraten.
Vergl. Physiol. Studien, 1, 77-155, 1 pl., 1 figure in text.

Lanepon, F. E.

1900. The sense organs of Nereis virens. J. Comp. Neurol., 10, 1-77, 3 figures

in text.
RETZIUS, G.

1895. Die Smirnow’schen freien Nervenendigungen im Epithel des Regen-
wurms. Anat. Anz., 10, 117-123, 7 figures in text.

1900. Zur Kenntnis des sensiblen und des sensorischen Nervensystems der

Wirmer and Mollusken. Biol. Unters, 9, 83-96, pls. 16—22.
Roupe, FE.

1887. Histologische Untersuchungen iiber das Nervensystem der Chaeto-
poden. Zool. Beitrage, 2, 1-81, pls. 1-7.
SmIRNow, A.
1894. Ueber freie Nervenendigungen im Epithel des Regenwurms. Anat.
Anz., 9, 570-578, 3 figures in text.
STRAUB, W.
1900. Zur Muskelphysiologie des Regenwurms. Arch. ges Physiol., 79, 379—
399, 15 figures in text.

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‘UNIV ERSITY OF CALIFORNIA _ PUBLICATIONS — (Continued)

Notes on the Tintinnoina. 1. On the Probable Origin of Dictyocysta tiara

Haeckel. 2. On Petalotricha entzi, sp. nov., by Charles Atwood Kofoid.
Pp. 63-69; 8 figures in text. December, 1915. SS A A nay NERY OEY

. Binary and Multiple Fission in Heramitus, by Olive Swezy. Pp. 71-88,
plates 9-11,-

05.

On a New Trichomonad Flageliate, Price nomitus parvus, from the Intestine ;

“of Amphibians, by Olive Swezy. Pp. 89-94, plate 12.
Nos. 6. and 7 in one cover. December, 1915 20.
On Blepharcorys equi,-sp. nov., a New Cilia te from the Caecum of the
Horse, by Irwin C. Schumacher. Pp, 95-106, plate:i3. December, 1915...
‘Three New Helices. from California, by S.-Stillman Berry. -Pp. 107- 111,
January; 1916... pM E ehcp a OE NE a OO SE ODE SRM te Cone Patty ey eee ee
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the Wests of the Wood Rat Neotoma fuscipes, by Charles Atwood Kofoid
~ and Irene McCulloch. Pp, 113-126, plates 14-15. February, 1916 ...........:.
The Genera Monocercomonas and Pol, ymastix, by Olive Swezy.. Pp, 127-138,
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Notes on the Spiny Lobster (Panulirus interruptus) of the California Coast,

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Esterly,. Pp. 171184, 2 fioures in text. March, 1916 20:
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PAS-292.- Mates “LB-Ddec = SLY. Ot G so e.g ae OSs Se a
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‘Raymond Dice: Pp, 293-348, plates 24-26. . June, 1916s
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314-280; Plate S0.2% JanMar ys OLT Ge oes ee Se OS SS ae eect
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EM BABES ieee Conte toes cre anor tad Sg ta Ae Ea Wiech ss RC ae ee SO eG RN AP Sr aga
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ton Copepods when Certain Recurring External Conditions are Absent, by
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National Park, California, by Charles Lewis Camp. Pp. 11-14. Septem-
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A New Spermophile from the San Joaaain Valley, California, with» Notes:

on Ammospermophilus nelsoni. nelsont Merriam, py-Wailter P. Taylor. “Pp.
45-20, 1 fierein-pext. - October, 1916. C es 8 eee a crachacde Sits

Ns Habits and Food of the Roadrunner in. California, by Harold Cc. _ Bryant.

Pp. 21-58, plates 1-4,-2 figures in text. October, 1916 202.2022...
Description of Bufo canorus, a New Toad from the Yosemite National Park,
by Charles Lewis Camp. Pp. 59-62, 4 figures in text. ‘November, 1916...

. The Subspecies of Seeloporus occidentalis, with Description of a New Form

from the Sierra. Nevada and Systematic Notes on Other California
Lizards, by Charles Lewis Camp. Pp. 63-74. December, 1916 2.2...
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325

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= Joseph Grinnell and Charles Lewis Camp. Pp. 127-208, cS figures in text :
= PUIG ABET Skeid ee Nae Oe ee ae hn ae ye ene ie

Ty A Study of ihe. Races of the ‘White-Fronted ‘Gooke: cee albifrons) “Occur. a

ring in California, by H. S. Swarth and Harold c. ‘Bryant. “PR, 209- 222, 4

gerRtas +22 fpures in-text, plate 13. Ocpober 201 ra ness rs eA a ee,
Vol. 18. 1. Mitosis in Giardia Microti,: by William c. Boeck. “Pp, 1-26, ‘Plate 1 _ Octo- RS
; beh 11) we) GSN AF GA coer ar een me ter ne PRESS BRU re te ues cONERN EN ARDS MU ncm me ep emp ntene Mp "

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cisco Bay, California, by Albert L. Barrows.» Pp. 27-43, “December, 1917, — :
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Convivus Stal, by Trene ‘McCulloch. Pp. 75-88, 35 text figures. Decem- .

cus er 1917 <
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-Swezy. Pp. 89-102, 12 figures. in text. December, 1917 <220000 2-0. es

che Transmission of Nervous Impulses in Relation to Loconiotion: in the io
* Earthworm, by John F. Bovard. Pp. 103- 134, 14 figures in text. xs anuary, ee
sR Bs ae ian ie eet es RE A ape ACR SIMA pe pp tee Tee AEN geen SPER eS ONE OP
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135-144, 1 figure in text. January, 1918 222.220. tsecaeeceececeeeestien weoele @ 2% age
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UNIVERSITY OF CALIFORNIA PUBLICATIONS
IN

ZOOLOGY
Vol. 18, No. 8, pp. 135-144, 1 figure in text January 10, 1918

THE FUNCTION OF THE GIANT FIBERS
IN EARTHWORMS

BY
JOHN F. BOVARD

CONTENTS
PAGE
init O UC EY OM meee eet eee renee eet Lt RUN ae ee Ee SO ee Ae Ae 136
he Generale function syOt shletmerviel ¢ OTC ese sre sence reece nee eee 136
demas Ve German mass PIG OIG? oo seas ca ca et sacs ecet oe crea a oe am Se 136
2. Muscle not responsible for rhythmic movements ........................ 136
a. Hniediander’s theory, of giant fiber action 2.2! 222 yt 2 136
Wi berlalee nal demmet io deste Oc ea oe 1s eee ee, Remmi eees eee eas 137
eee Nica Goretelligits © le tomes eee err cten sof este 225552 a ee ee eee see 137
HTM HOGS Cdl en ee ee ecco b oe chap ccs Senta nnn ctnt wetness eee siveccouee ace ce acer 137
HeeRE Om ELAM SOCULOED 282k. be io. Socata Sethe NR Soleo aoe es 137
25 hemovall of, short sections of the cord)... 222.522 ae 137
Sbitectisnotebhesoperatlom amd! TECOVET Ys sees seen ere 138
ROMEHETALTON CORPO LUM CTERS: fe: cated anemone cae ncaa cence acer deg tees anmereae ce 138
Heprirectsnolsumpler transverse SGCtION, | ......2crscre ete soe ee 138
I; Recovery of activity. of. locomotor fibers)... 2-0-2. -e-ce---- 139
Zo eRecovery, Of activity Of giant bers: 20s ee eee 139
iemtvemovaluoumshorbs pveces! Ot cblle CON steer eee ee ee eee ee were e acces 140
1. Recovery of locomotor fiber activity -.. ee Ti nie hrertee aati ot 141
2. Recovery: of giant) fiber activity -2x.2222 5 eh ee 142
III. Comparison of results with those of Straub and Friedlander -...... =, 142
RESP eR EMSEE SSe GWG EL SI OWED LO) San ec a alee ee Bet ne eee eee nen cceace 143
INAV es Gila: GS pee) Uc eae oe teen eee Ne see ee pipes Nett the Wes Jt Stet ee tat ee 143
My ec overys Trom (Omects Ol) ATU GS face ere eee eee ces temsene ene 143
Ty IBM lvalore Cit way Wayoroneayaneane NOE AS) <a oe cee cee cet ceeet eeeeee 143
Qe Behavior ot awe. olanite hi ens sees re Pett tise Me PEE 2052 143
SU FIE TG TE ee ce ore a aN Sa 2 ceca RU ee ec ee Vidi

BU arts ea Arts WETS oy Cu ts Cl pate mee ae ate tees cee i acral Dr Cees Cae NMOS Se ooh dant agen Auee iets 144

136 Unversity of Califorma Publications in Zoology [Vou. 18

INTRODUCTION

In the analysis of the locomotion of the earthworm Friedlander
(1894) showed that worms made well co-ordinated movements even
after considerable portions of their nerve cords had been removed.
He concluded that the nervous system served simply as a medium for
very short relayed reflexes and played a secondary part in locomotion.
Biedermann (1904) extended this idea by showing that stimuli could
run long distances in the cord, and in my recent paper (1918) I was
able to show something concerning the limits of this transmission and
also the rate at which such impulses travel in the cord when not
reinforced from without.

Straub (1900) claimed that the spontaneous contractions of short
sections of earthworm were due to inherent qualities of the muscle;
at least they were not due to the nervous system present. My own
experiments seemed to show a contrary result, and in all cases rhythmic
movements were only in pieces containing nerve cord.

The results of these experiments just cited were obtained on worms
from which the nerve cord had been entirely taken away. It occurred
to me, therefore, to study the effects of regenerating nerve cord on
locomotor movements. It is well known that the nerves do not all
regenerate in the same time, and this, then, would give me some clue
as to which fibers carried locomotor responses and which the end to
end collapsing movements. Friedlander (1894) suggested that the
quick jerks which take the animal back into its burrow were due to
impulses carried by the giant fibers. This has been accepted as most
probable, but has not been demonstrated. If, then, a regeneration of
the nerve cord would give a differential healing, it would be probable
that the giant fibers would unite sooner or later than the transmission
nerves, and we would have some definite proof for Friedlander’s
contention.

The effects of simple transverse sections of the ventral cord were
studied and later short portions of the cord were removed. Drugs,
such as stovaine, were also tested, because they have the effect of
‘‘plocking’’ the nerve cord, which is practically the same as removal
of ganglia for a brief time. Drugs have the added advantage of losing
their effect quickly, and so the changes in nerve reactions during
development and recovery from the anesthesia could be watched.

1918] Bovard: Giant Fibers in Earthworms LBV

MATERIALS AND METHODS

Material—Both the common Allolobophora foetida and Helodrilus
caliginosa were used in these experiments. Similar results were ob-
tained with each, but in general the larger worm was the easier to
work with, especially when operations were made for the removal of
sections of cord.

Methods.—In all cases where operations were to be performed the
worms were kept for at least twenty-four hours in clean moist cloths,
so they would clear themselves of dirt and grit. Worms that were
kept in moist filter paper usually ate large quantities of this, which
made the cutting of sections quite difficult.

The transecting of the nerve cord was a simple operation. The
worm was held tightly on a moist surface and a transverse cut made
with a safety razor blade. A single stroke was usually sufficient to
eut both ventral muscle and the nerve, and if care were exercised
there was little danger of cutting too deep. The cut was examined
with a hand-lens to make certain that the cord had been cut.

A simple physiological method of determining whether the cord
had been sectioned, and a method that proved a check on all experi-
ments, was as follows: Examination of the worm immediately after
the operation showed that the muscles posterior to the cut had lost
their tone, giving an increase in the diameter of the part. This con-
dition did not extend for any great distance, but was usually confined
to from three to five segments. If the nerve had not been severed,
this effect wore off after the first day of regeneration; otherwise it
remained enlarged until physiological continuity was re-established.

In operating on Helodrilus, a simple transverse cut with a razor
blade usually only severed the musculature. The cord adheres very
closely to the intestine and comes away from its ventral muscles very
readily. In these cases it was necessary to cut the cord with a pair
of fine scissors, making a simple snip. Where care was not used and
the ventral blood vessels were cut also, the animal bled profusely, and
in many cases died or autotomized the posterior piece.

When necessary to remove two ganglia, the worms were anesthet-
ized in a 5 per cent alcohol solution for fifteen minutes to one-half
hour, in all cases until they were motionless. Under a dissecting
microscope, a transverse cut was made in the ventral muscles. The
opening was stretched and pinned back with clean, fine needles. The
nerve cord and bloodvessels then could be easily seen. Great care

138 University of California Publications in Zoology [Vou.18

had to be exercised to prevent cutting any blood vessels. The cord
was lifted up with fine forceps, and a cut made anteriorly. The cord
could then be pulled forwards and a cut made posteriorly. The seg-
ment, which was removed, was then put into 95 per cent alcohol and
examined later to ascertain the exact amount of nerve substance re-
moved.

After the operation the worms were placed in small 8-ounce jars
with some moist cloths over them and put away in a dark cabinet.
It was not found necessary to keep the worms in a particularly cool
place as long as the jars and cloths were kept scrupulously clean. The
temperature was the ordinary room temperature during April and
May in the Harvard laboratories. The only cases where worms died
during these experiments were those which bled profusely after the
operation due to rupture of the large ventral blood vessel. The loss
was surprisingly small.

By the following day the worms appeared normal, the wound had
healed over and they could be seen creeping about in the jars. Usually,
however, they were not very active in the cramped quarters of their
jars.

EFFECT OF TRANSVERSE SECTIONS OF THE CorD

The result of simply transecting the cord was the loss of trans-
mission and of the animal’s power to reverse its direction of creeping
on stimulation. Stimuli applied at either end ran as far as the cut,
but failed to pass across the break in the cord. Earthworms often
respond to strong stimuli given to the anterior end by certain lashing
movements and side to side jerks. When the cord was severed these
lashing movements could be induced in the anterior portion of the
worm without producing any effect on the posterior part behind the
eut, which might lie quiet during this movement. Giant fiber action
induced either from the anterior or the posterior direction was effective
as far as the cut only. The quick, end to end action never succeeded
in starting the same kind of a movement in the portion of the worm
on the other side of the break opposite to the point stimulated.

The effects on the musculature were particularly noticeable. lmn-
mediately behind the cut region the worm showed an enlargement of
the segments. Here the circular muscles seemed to have lost their
tone. As the worm crept along the posterior part acted in co-ordi-
nation with the anterior, but these few segments behind the cut took
no part. The length of this inactive part varies from three to five

1918] Bovard: Giant Fibers in Earthworms 139

segments. Behind this, normal creeping movements were seen as the
nerve regenerated and the lost function was restored. This appear-
ance of the cut region disappeared as the normal reactions returned.

REGENERATION

The regeneration of the nerve was remarkably rapid. Sections
of a worm (Allolobophora foetida) prepared after two days of regener-
ation showed that the nerve fibers had penetrated into the regenerating
tissue and had formed across the gap. And on the third day the
physiological reactions were being transmitted up and down the cord.
The reversal of the direction of creeping was easily possible on stim-
ulation. The giant fiber reactions, however, were not yet possible.
Any stimuli which called out such reactions in the anterior part of
the worm ran only as far as the cut, and the same is true of reactions
started in the posterior part. However, on the fourth day and fifth
day the giant fiber action was restored for the entire worm, which in
all respects gave normal reactions.

In the large Helodrilus, the same relations were found, except that
the period of regeneration was a little longer. The return of the
locomotor transmission occurred usually from the fourth to sixth day
after the operation and the giant fiber action on the following day.
The regeneration of nerve cord in this large worm shows a very inter-
esting thing in this return of the activity of the giant fibers. Twenty-
four hours after the return of locomotor transmission, one can look
for giant fiber action. This makes its first appearance as an impulse
traveling from anterior to posterior, and it is not until some hours
later, usually the following day, that this action is transmitted in the
opposite or postero-anterior direction.

In testing worms for the return of locomotor transmission through
the cut area it will be noticed that in the early stages posterior creep-
ing may not be the response on stimulating the anterior part. How-
ever, if several stimuli are given, summation takes place and a pos-
terior movement takes place. At other times the result of a stimu-
lation may be shown in the contraction of the circular muscles and
elongation of the posterior tip, a movement preparatory to creeping,
without the movement being completed by a well organized. reaction.

The first indication of the return of giant fiber transmission is a
condition that shows the antagonistic innervation of muscles that has

been shown for vertebrates.

140 Umversity of California Publications in Zoology [Vou.18

The following table, no. 182, shows a series of worms and regen-
eration of nerve cord as expressed by the return of physiological
activity.

EXPERIMENT 182—REGENERATION OF NERVE Corp AFTER A SIMPLE TRANSVESE

SECTION
Time in days when impulses are again possible in Transmission Fibers and Giant Fibers

Locomotor Locomotor Giant Giant

trans. trans. fiber fiber

Worm Ae PHA: Aa pA

A 3 3 3

B 3 3 Bx oe
C 3 3 4 5
D 3 3 5 6
E 3 3 4 5
F 4 ~ 5 6
G 4 4 5 Uf
H 4 4 5 6
i 4 4 5 5
J 4 5 8 10
K 4 4 5 5
L 5 5 6 6
M 5) 7 10 —
INA Se 5 5 6 8

A P= transmission from anterior end to posterior end.
P A=transmission from posterior end to anterior end.

Stimulation of the anterior end causes the end to end jerk of
muscles as far as the cut, but behind this no such movement arises.
With each stimulus there will be seen, in the posterior tip, a relaxation
of the circular muscles and a dorso-ventral flattening. The chaetae
will be projected and directed forwards, but there is no movement of
the longitudinal muscles. A few hours later the Same movement will
be accompanied by a distinct jerk of the longitudinal muscle, and the
next day a well co-ordinated, end to end contraction will be added to
the reaction.

REMOVAL OF SECTIONS OF THE CorD

When small sections of the cord were removed, as shown in the
following table, the return of physiological activity was in the same
order as when simple transverse sections were made. The time for
regeneration and complete recovery was lengthened, but was still sur-
prisingly short.

eli

1918] Bovard: Giant Fibers in Earthworms 141

EXPERIMENT 191—REGENERATION OF NERVE Corp AFTER REMOVAL OF SHORT
SECTIONS OF CoRD

No. of Trans. Locomotor Giant Giant
ganglia locomotor trans. fiber fiber
Worm removed INO S22 Pea AC PA
A 2 6 6 9 9
B 13 4 4 10 i3t
C 2 % Dead 22 oe
D 23 Les) Dead cae =
E ie 4 4 5 6(2)9
F 2 4 4 9 9
G 14 a Dead a ad
H 1 9 9 12 13
i 13 4 4 5 6
J 1 5 Dead = ane
K 1 ce Dead —_ a
L 2 9 9 10 anti
N 2 4 4 5 6(2)9

A P refers to locomotor impulses passing from anterior to posterior.
PA refers to locomotor impulses passing from posterior to anterior.

c= + ——

~
od

--—---int. epith.

l. m.

SN Crailvs

Grae

---ch. sh.

1--- Spt.

Fig. 1—A camera lucida drawing showing the union of the cut ends of the
ventral nerve cord. X 42. Experiment 191, line 1. In this worm two ganglia
had been removed and nine days given for regeneration. Normal locomotor
transmission and giant fiber action had returned. ch. sh., chaeta sheath; cir. m.,
circular muscle; ctx., cicatrix tissue; epi., epidermis; g.f., giant fiber; int. epith.,
intestinal epithelium; /. m., longitudinal muscle; n.c., nerve cord; n.sh., nerve
sheath.

142 University of California Publications in Zoology [Vou.18

Figure 1 shows a longitudinal section of a worm that showed
normal locomotor transmission and giant fiber action after nine days
of regeneration. Two ganglia had been removed. In some eases the
regeneration was more rapid and in some slower, so this figure repre-
sents a typical case.

It was expected that the removal of short sections of the cord
would lengthen the time between recovery for locomotor transmission
and giant fiber action. But this was found not to be the case, for, in
general, the responses of end to end contractions recur about twenty-
four hours after the locomotor transmission reappears. Here, as in
the regeneration from simple transection, the giant fibers gave impulses
in the antero-posterior direction in advance of those in the opposite
direction. While removal of short pieces of cord lengthens that period
of regeneration in which no transmission of impulses is possible, it
changes very little the order and time of events after the union of the
cord is established.

The remarkable facility with which these worms regenerate lost
sections of nerve cord has an interesting bearing in the experiments
of Friedlander (1894) and Straub (1900).

After the removal of ten to twelve ganglia from the nerve cord,
Friedlander (1894) allowed the worm two to four weeks before he
discarded them for use in his experiments. My results would indicate
that he was not dealing with segments entirely free from nervous
transmission, for, while the nerve cord may not have entirely regen-
erated, it is certain that it could have grown considerable distances
into the region, even if it had not grown across the gap. This would
make a marked difference in interpreting experiments of co-ordination
of anterior and posterior pieces, especially if nearly four weeks had
been given for regeneration.

Straub (1900) claimed that annelid muscle would give rhythmic
contraction if the nerve cord were dissected out. In this case, sections
of twenty to thirty ganglia were removed and the worms given eight
days to recuperate. In this short time the nerve probably could not
grow the length of such a gap, but could grow into the area for a
considerable distance from the end of the nerve stump. When he cut
out the operated part and used this to show rhythmic contractions,
it is Just possible these segments may have contained some regenerated
nerve elements. Budington (1902) has shown that segments of worms
containing even small fragments of nerve will give these rhyihmie
contractions, but when the ventral wall is removed no such contrac-
tions can be induced.

IIE EIOEDEEEED DEO

1918] Bovard: Giant Fibers in Earthworms 143

EFFECT OF DRUGS

If small quantities of cocaine or stovaine are injected into the
body cavity of the worm the drugs act as a block on the nerve and
affect the transmission through the nerve cord. Cocaine has a more
general effect on the worm and produces in many eases very irregular
behavior, but stovaine gives very consistent results. The first effect
was the loss of giant fiber action through the region. Transmission
was perfect above and below the point of injection. As the effect of
the drug worked deeper into the cord the transmission of locomotor
impulses became more irregular and in some cases was lost altogether.
As recovery took place the return of activity was just the reverse.
The locomotor impulses became more and more regular until perfect
co-ordination was set up. Then the giant fiber action began to show
transmissions. Here, too, the same phenomena were seen as in the
case of regeneration. Just before giant fiber impulses showed normal,
end to end responses, the stimulation of the anterior end showed the
characteristic relaxation of the circular muscles in the posterior tip.
Very soon after this the end to end movements occur in response to
stimuli.

A record is given below of an experiment with stovaine, which
shows the course of events and the relation between giant fiber and
locomotor fibers.

EXPERIMENT 188—EFFECT OF STOVAINE ON TRANSMISSION

May 18, 1915, 4:45 p.m.—The worm (Helodrilus caliginosa), doubly pinned to a
cork plate on a glass, was injected with a small quantity of stovaine in
the body cavity of the middle region.

Almost immediately giant fiber action is lost and locomotor trans-
mission not normal.

5:00 p.m.—Locomotor impulses pass through block, but do not run full length
of posterior part.

Locomotor co-ordination between anterior and posterior parts.
As time goes on locomotor movements run further down the posterior
part.

5:10 p.m.—Any stimulus to the anterior end results in locomotor movements
in posterior end. Wave contractions run to posterior tip more frequently.
No giant fiber action.

5:35 p.m.—Stimulation of anterior end gives increased activity of posterior
end. No giant fiber action. Animal apparently normal except no end to
end contractions.

5:48 p.m.—Giant fiber action returned. Animal fully recovered.

144 Umversity of Califorma Publications in Zoology [Vou. 18

SUMMARY

1. After transverse section of nerve cord, locomotor transmission
fibers regenerate before giant fibers.

2. The period of regeneration after a simple transection is very
short, from three to four days.

3. Removal of short pieces of the cord gives the same results as
simple transverse section, except that the period of regeneration is
prolonged. ;

4. The effect of drugs, such as stovaine, on the cord shows that
the transmission fibers may be active, while the giant fibers are still
under the anesthetic. Recovery is in the same order as is shown in
regeneration.

5. The general result of this study shows that the giant fibers are
concerned with other functions than locomotion, and that locomotor
transmission fibers lie deep in the cord.

LITERATURE CITED
BIEDERMANN, W.

1904. Studien zur vergleichenden Physiologie der peristaltischen Bewegun-
gen. I. Die peristaltischen Bewegungen der Wiirmer und der Tonus
glatter Muskeln. Arch. ges. Physiol., 102, 475-542, 1 figure in text.

Bovarp, J. F.

1918. The transmission of nervous impulses in relation to locomotion in the

earthworm. Univ. Calif. Publ. Zool., 18, 103-134, 14.
BuDINGTON, R. A.

1902. Some physiological characteristics of annelid muscle. Am. J. Physiol.,

7, 155-179, 16 figures in text.
FRIEDLANDER, B.

1894. Beitriige zur Physiologie des Centralnerven systems und des Bewe-
gungsmechanismus der Regenwirmer. Arch. ges. Physiol., 58,
168-206.

STRAUB, W.

1900. Zur Muskelphysiologie des Regenwurms. Arch. ges. Physiol., 79,

379-399, 15 figures in text.

~ wewKr te a

24.

2

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UNIVERSITY OF CALIFORNIA PUBLICATIONS
IN

ZOOLOGY

Vol. 18, No. 9, pp. 145-149 December 24, 1917

A RAPID METHOD FOR THE DETECTION OF
PROTOZOAN CYSTS IN MAMMALIAN
FAECES

BY
WILLIAM C. BOECK

Cropper and Row (1917) have recently given an account of a
rapid method of concentrating the cysts of Hntamoeba in human
stools. This method has since been applied also to the concentration
of the cysts of flagellates, principally those of Giardia intestinalis, by
Carter and Matthews (1917). The method is based upon the principle
that if ether is stirred into an emulsion of faecal material and normal
saline solution and the mixture then placed in a separating funnel,
the debris, having absorbed the ether, will float in the layer of ether
which soon rises above the layer of normal saline solution, while the
eysts will remain below. These cysts may then be procured by draw-
ing off the saline solution at the bottom of the separatory funnel and
concentrating them subsequently by centrifuging.

In a paper by Carter and Matthews (1917) an account is given
of a fair trial of this method of concentrating cysts from stools. They
conclude that the method ‘‘is more severe than the ordinary method
of examination of a faecal emulsion: that when the method is used
at the time the third ordinary examination is made a result is given
which would probably be obtained by five ordinary examinations. The
method is impracticable, however, when a large number of stools have
to be examined each day, for the time required to make these concen-
trated examinations is not commensurate with the results obtained.’’

It is more important, however, to realize that the efficacy of the
method is not in the least impaired by these conclusions, and that the
method would be more practicable if the time involved in’ making the
test could be shortened.

146 , University of California Publications in Zoology — [Vou. 18

In my work on the detection of the cysts of Giardia microti, a
species found in rodents and similar in structure and size to Giardia
intestinalis of man, I have used certain modifications of the Cropper
and Row method, which I believe are improvements not only by saving
considerable time in making the examination but also of enhancing
the accuracy of detection of the cysts of Giardia and of other Protozoa
in the stools. This method has been tested with success on human
stools in the Biological Laboratory of the California State Board of
Health. :

The first change in the method, and one that saves considerable
time, is the employment of the Hamilton-Beach ‘‘Cyclone’’ electric
mixer for emulsifying the stools. This device may be seen in use in
mixing drinks at most soda fountains. It commends itself very favor-
ably because of its rotary action and its speed in beating up an
emulsion. This action favors the mingling of all parts of the stool
into a condition in which the eysts are uniformly distributed. The
instrument shortens the time of thirty minutes prescribed by Cropper
and Row (1917) as necessary when the stools are to be shaken into
an emulsion to not more than ten minutes. Naturally the time element
here is dependent upon the firm or the liquid consistency of the stools.
The action of emulsification may be accelerated by fastening a wire,
looped back and forth in a single plane, to the rim of the glass con-
taining the sample of the stool in the normal saline solution so that
it projects down into the mixture. This simple device is of great
service in that it helps to break up any lumps that may occur in the
faeces. I have found that this mixer beats up a fairly uniform
emulsion and is entirely satisfactory in liberating the cysts from the
lumps in the stools. This wire loop was devised by Mr. J. D. Me-
Donald, Assistant in the Biological Laboratory of the California State
Board of Health for use in the examination of human stools for hook-
worm. I am greatly indebted to him for the suggestion of using the
looped wire in order to break up the lumps in the stools, and to
Professor C. A. Kofoid, Director of the Biological Laboratory of the
California State Board of Health, for the permission to publish this
note regarding the method of examination of stools in use in that
laboratory.

Another change in the method is in the use of neutral red to stain
partially and to differentiate the cysts from the debris and from the
intestinal yeasts. The use of this stain in making diagnosis of faecal
material was first suggested by Stitt (1911). I have used two methods

1917] Boeck: Protozoan Cysts in Mammalian Faeces 147

in the application of this stain. In the first, one gram of faecal
material in thirty cubic centimeters of normal saline solution is
emulsified by means of the electric mixer for about eight minutes.
About five cubie centimeters of neutral red solution N/10,000 are then
put into the emulsion, which is stirred until it is of a uniform reddish
color. Five centimeters of ether are then stirred into the emulsion.
The remaining steps of the process of concentration follow at once.

In the second method of appleation of this stain, a drop of the
neutral red solution may be applied to a very small amount of residue
containing the cysts and placed on a slide, preparatory to microscopic
examination. The residue is obtained by centrifuging the saline solu-
tion which had been drawn off at the bottom of the separatory funnel.
In the latter method of appheation of the solution of neutral -red
there results a greater intensification of the stain in the debris, afford-
ing a sharper contrast between debris, yeasts, and the cysts. The
cysts may take at the most only a light pink stain, due to their wall,
which prevents penetration of the reagent. In many eases the eysts
are not colored at all, even by this intensive method of treatment.

The use of this stain, however, helps to cut short the time necessary
for making the examination, since one is able to detect the cysts with
great celerity and accuracy because of the sharp contrast that is
presented between the cysts, the yeasts, and the debris. The yeasts,
on the other hand, are usually entirely stained, but if not, the stain
can be seen in the central vacuole, which at onee differentiates the
yeasts from protozoan cysts of the same size in which the structure
of the contained organism may be indistinct. Since, however, only
a slight amount of stain is wont to differentiate the internal structures
of protozoan cysts, one is able by the use of the neutral red to dis-
tinguish the nuclei, axostyle, and the remains of the intracytoplasmic
flagella in the cysts of Giardia more quickly than without the use of
the stain. It is this feature which adds to accuracy in the detection
of these cysts.

The method in full as I have been using it is as follows: Take
at least one gram of the stool to be examined, place it with thirty
eubie centimeters of normal saline solution in the mixing glass and
stir for at least ten minutes, pouring in five cubic centimeters of
neutral red solution N/10,000 at the end of eight minutes, if one
desires to use the stain at this time in the method. At the end of ten
minutes, while still stirring, add five cubic centimeters of ether and
stir two or three minutes longer.

148 University of California Publications in Zoology [ Vou. 18:

A general rule may be laid down here at this time. The ether
tends at first to settle the emulsion temporarily, but at the end of
about two minutes the emulsion begins to rise up and foam again
because the ether becomes localized by absorption in the debris. In
order then to get the best results and to be assured of the greatest
possible flotation of ether-soaked debris, one should cease stirring at
the very moment the emulsion commences to foam again. Then the
emulsion should be hurried into a separatory funnel and allowed to
stand for at least five to seven minutes, during which the eysts will
settle to the bottom in the saline solution and debris will float in the
ether above. The funnel used for this separation has a funnel-shaped
bowl with steep sides contracting to a narrow neck above the turn-
cock.

At the end of this period of standing, the saline solution, about
fifteen cubic centimeters, is drawn off at the bottom of the separatory
funnel into a centrifuge tube of a capacity of fifteen cubie centimeters,
and is centrifuged for three minutes at 1600 revolutions per minute.
The supernatant fluid is then drawn off and the residue is examined
microscopically for the cysts. At this time a drop of neutral red is
applied to a small amount of this residue preparatory to microscopic
examination if the stain has not been used previously. It is preferable
to use it at this time in order to procure a sharper contrast between
the cysts and the surrounding debris.

By this method a faecal examination can be completed in twenty-
five to thirty minutes, which is considerably less than the time required
by the method which Cropper and Row (1917) described. Although
I have been especially interested in the application of this modification
of their method to the detection of the cysts of Giardia, I have noticed
at the same time that it is equally applicable to the detection of cysts
of Entamoeba, of other flagellates, and of the eggs of nematodes, which
I have found in the faeces of the rat.

The great value of this method of concentrating cysts of protozoan
parasites is realized when one desires the most accurate diagnosis of
a suspected case.

A high degree of infection by both amoeba and flagellates is
reported by Dobell (1917) from both dysenteric and non-dysenteri¢
convalescents from the Mediterranean area in British hospitals. Each
infected individual might become the source through unsanitary con-
ditions for further distribution of the disease among the troops should
he return to the front, or possibly to civilians on his return to private

1917 | Boeck: Protozoan Cysts in Mammalian Faeces 149

life. All devices, therefore, which can assist in the certain and rapid
detection of such carriers, not only of those under military conditions
but of all persons returning from regions of dysenteric infections,
have a preventive value, especially in view of the enhancement of the
risks of contagion due to the present conditions in Europe.

LITERATURE CITED

CROPPER, J. W., and Row, R. W. H.

1917. A method of concentrating Entamoeba cysts in stools. Lancet, 192,
179-182.

CarRTER, H. F., and MarrHeEws, J. R.

1917. The value of concentrating cysts of the protozoal parasites in exam-
ining stools of dysenteric patients for pathogenic entamoebae. Ann.
of Trop. Med. and Parasitol., 11, 195-205.

DOBELL, ©: C!

1917. Reports upon investigations in the United Kingdom of dysentery
cases received from the Eastern Mediterranean. I. Amoebie dysen-
tery and the protozoological investigation of cases and carriers.
Medical Research Committee, Special Report Series no. 4 (London,
H. M. Stationery Office), 85 pp.

Stiirt, E. R.

1911. Practical bacteriology, blood work and animal parasitology, ed. 2
(London, H. K. Lewis), xiii, 345 pp., 91 figs. in text. See pp.
299-304.

“UNIVERSITY oF CALIFORN Ia PUBLIOATION S—(Continued)

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$. On Binary and Multiple Fission in Giardia muris (Grassi), by Charles
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Nos.2 and-3 in one cover. November 1915 ......... PINE SS
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NS eee Toe aE I eee aes Re tee oe ee eed kre

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138; plates 16-19. “February, 1916 <5.) cs es

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Calvin 0. Esterly. Pp. 171-184, 2 figs. in text.. March, 1916-22... seal

15. The Kinetonucleus of Flagellates and the Binuclear Theory of Hart-
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=. 16..Cn the Life-History of a Soi! Amoeba, ey, Charlie Woodruff Wilson.

Py. 241-292: plates: 18-25. -Suly, 1016 ee
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18. The Anatomy of Heptanchus maculatus >. the Endoskeleton, by a.
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21. The. Occurrence of a Rhythm in’ the Geotropism ‘of Two. ‘Spectes of BS ee
Plankton Copepods When Certain Recurring External Conditions are ===
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22; On Some New Species of Aphroditidae from the Coast of California, =
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23, Notes on the Natural History and Behavior of Emerita analoga (Stimp-
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1. Mitosis in Giardia Microti, by William C. Boeck. Pp. “1-26, plate 3

OCs NTT TO a al ia saan laa eg te gta ae a

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Faeceés, bE William C. Boeck, Pp. 145-149. December,. 1917". ees ray .05

UNIVERSITY OF GALIFORNIA PUBLICATIONS
IN :

? ZOOLOGY
Vol. 18, No. 10, pp. 151-170, 12 figures in text March 9, 1918

_ THE MUSCULATURE OF HEPTANCHUS
oe MACULATUS

BY

PIRIE DAVIDSON

UNIVERSITY OF CALIFORNIA PRESS
“‘BERKELEY»

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UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN
ZOOLOGY
Vol. 18, No. 10, pp. 151-170, 12 figures in text March 9, 1918

THE MUSCULATURE OF HEPTANCHUS
MACULATUS

BY

PIRIE DAVIDSON

CONTENTS

PAGE
TEvauRTCONO TOK NO, ose Eee Ea tA ne ee eee ee (AE Ld Ae See ee eer 151
WMS WHORE ese ces e ae ca ae ge 20a aL 151
BETES E Onna all meee sees ee a ere Nee oY Pe Ae ee ee eennceres 8) ee et NE at 152
‘GRAN. TERTERSXOUU ELUTE) = eo eee te ee ce Als Sa ee 152
Hes Hedin yet @ ea Meerut S GU) ea VT © yee see etc ec etree eee Chane e aera 152
SS UD Feral ten Lex Ce CUM eh Teas TOUTE S C'S ene ene oe eee sees een . Los
SUT Bevo OU WSET ect se RO a ee A a 158
PSI ESS ov e121) Ys) A SR eo ae A eyo SRS Re SP Pn 5 ee ee eee 159
DAV GH GUNG; O13 pene oe ee eet cc cee Ed OP hae ee ae Pe ho choos cee as tee 159
ME Testo RJ) NrearW CAE AES we nee ee an Se et PO oc Seet iene tendon sesonesdede 161
Musculature associated with the organs of special sense —................------ 162
NTO; ORLA WOT Fore MTNA W VOR) ese RE Ee no ee EP 163
METS eral] easG 110, Oar tems ES att, UN ce ees te ree rs er coe ee Ee anne nse nerese anoe ES 167
Birirtie Trev tsLIOs © is Gilt © Cl esee eee re tee Seats Pca A eer eset funk i ee ee cae Meh Seep een deans nsec teeats 170

INTRODUCTION

For several years past work has been in progress on the various
systems of the elasmobranch fishes in the Zoological Laboratory of
the University of California and at the Scripps Institution for Bio-
logical Research at La Jolla. Material is easily obtained and many
types have been studied, both of the sharks and of the rays. The
seven-gilled form has been of particular interest because of its sup-
posed generalization.

MATERIAL

The seven-gilled form of the Pacifie coast is Heptanchus (Notorhy-
nchus) maculatus. It is dark gray dorsally with black spots, and light
colored ventrally, and may readily be recognized by the presence of

152 University of California Publications in Zoology [Vou. 18

seven large gill-slits which decrease in size posteriorly. It is a large
form, some of the specimens taken having reached nine feet in length.
For the greater part of this study small specimens of about two to three
feet in length were used. This work was suggested by Professor J.
Frank Daniel, to whom the author is indebted for assistance and
criticism.

HistToricaL

The literature on the pharyngeal musculature of elasmobranchs
is scanty. Vetter (1874) deseribed the pharyngeal musculature of
Heptanchus cinereus, Acanthias vulgaris, and Scymnus lichia. Ties-
ing (1896) published a paper on the musculature of the rays. Marion
(1905) wrote a paper on Acanthias vulgaris and the skate, Raia
erinacea, in which he drew comparisons between the musculature of
sharks and rays. Tuiesing classified muscles on the basis of ennervation
and this is perhaps the most reliable single criterion although it has
its disadvantages. Vetter and Marion used position and function,
which plan is followed in this paper.

This work agrees as a whole with previous publications although
slightly different interpretations are offered in a few instances. The
various organs of Heptanchus seem to agree remarkably well with
those of Hexanchus griseus as described by Ruge (1897) in an article
on the facial nerve in vertebrates. There are many articles on the
paired fins of selachians, but these deal mainly with their origin and
relation to the paired limbs of the higher vertebrates. The papers of
Krall (1908), Goodrich (1906), and Erik Muller (1909) have been
particularly helpful. The bibliography on the body musculature is
large, but several of the more important articles, including those of
Johannes Miller and A. Schneider, have not been available.

THE MUSCULATURE

The musculature may be divided as follows:

Pharyngeal musculature.

Musculature associated with the organs of special sense.
Appendicular musculature. |
Musceulature of the trunk.

PHARYNGEAL MUSCULATURE

This group includes the muscles anterior to the pectoral girdle.
These muscles are very much specialized, but still retain some of their

1918] Davidson: The Musculature of Heptanchus maculatus 153

primitive characteristics. They are concerned chiefly with respiration
and food getting, and include the following groups:
I. Superficial circular muscles.
Il. Interareuales.
III. Subspinalis.
IV. Adductors.
V. Hypobranchials.

I. THE SUPERFICIAL CircuLAR Muscues (fig. 1). The superficial
circular muscles form an almost complete muscular covering of the
pharyngeal region. In general they are thin and flat with fibers
running around the pharynx. The function of this group of muscles
is to constrict the pharynx and close the gill-clefts. Several series
of muscles are included in this division, some of which are very closely
connected in origin, insertion, and function.

csd. csd.?

Uj Varn

( 6 3°

|.mx.

Fig. 1. Head of Heptanchus maculatus, lateral view (X 3%). a. md., adductor
mandibulae; a. pr., antorbital process; csd.‘*, first to eighth dorsal constrictors;
lls... first and second parts of levator labialis superioris; I.ma., levator maxillae
superioris; md., mandible; po. o., postorbital process; p-q., palatoquadrate car-
tilage; sc., scapula; sp., spiracle; tr., trapezius.

1. Levator maxillae suwperioris (l. mz., fig. 1). The levator maxil-
lae superioris is described first in this group as it seems to be an
anterior continuation of the dorsal constrictors, and to share their
function. It consists of a group of short fibers having its origin under
the supraotic crest just posterior to the postorbital process. Its diree-
tion is ventral and anterior and it is inserted on the anterior and
dorsal edge of the enlarged quadrate region of the upper jaw just
anterior and continuous with the insertion of the first dorsal con-
strictor. Its function is to raise the upper jaw.

2. Superficial constrictors. The superficial constrictors form a
thin muscular layer almost completely covering the branchial region.
This group is divided for convenience of description into a dorsal

154 University of California Publications in Zoology — |Vou- 18

and ventral part. This division, however, is not a natural one for the
fibers, except in the case of the first and second divisions, are con-
tinuous from the dorsal to the ventral part.

Dorsal constrictors (csd. 1-8). The dorsal constrictors have a con-
tinuous origin extending from the cranium, just back of the postor-
bital process, to the pectoral girdle. The anterior part of the origin
is from the cranium, but the main part is from the sheath of connective
tissue which covers the trapezius and dorsal longitudinal muscles of
the pharyngeal region.

The first dorsal constrictor (esd.*, fig. 1) is continuous with the
levator maxillae superioris, but the fibers of the two have a different
direction. Its anterior extent is diffeult to determine in Heptanchus
maculatus, but it is limited posteriorly by the spiracle. Its origin is
on the cranium posterior to the origin of the levator maxillae supe-
rioris, and in the connective tissue described above. The fibers of the
first dorsal constrictor are slightly shorter than those of the levator.
It is inserted along the dorsal edge of the quadrate posterior to, and
continuous with the insertion of the levator maxillae superioris. The
two muscles function together in raising the jaw and constricting the
spiracle.

The second dorsal constrictor (csd.*) is the largest of the dorsal
series. It lies between the spiracle and the first gill-slit. Its origin
is continuous with that of the first dorsal constrictor. The anterior
deeper part is inserted on the middle of the dorsal segment of the
hyoid arch. The main part of the muscle is inserted dorsally on the
palatoquadrate from the insertion of the first of this series to the
angle of the jaws. The fibers between the angle and the gill-slit are
continuous with those of the corresponding part of the ventral series.
In passing over the median cartilaginous rays the fibers become
tendinous.

Dorsal constrictors®* have a similar origin and extent. They de-
crease In size posteriorly corresponding to the decrease in size of the
branchial apertures. Their origin is continuous in the connective
tissue sheath of the trapezius. Their fibres run ventrally and are
continuous with those of the corresponding ventral constrictors.

Ventral constrictors (csv. 7-8, fig. 1). There is a difference of
opinion concerning the naming of the ventral constrictors. Vetter
(1874, pp. 409-416) describes them for both Acanthias and Hep-
tanchus and does not recognize a first ventral constrictor in either
form. Marion (1905, pp. 7-8), although saying nothing of Heptan-

Or
Or

1918} Davidson: The Musculature of Heptanchus maculatus ale
chus, divides the ventral constrictor group in Acanthias into six parts
corresponding to those of the dorsal group. The part which he calls
the first, is known as part of the second ventral constrictor by Vetter.
Marion names the part inserting on the first visceral or mandibular
arch the first, and that on the hyoid arch the second. There seems
to be some doubt that these are separate muscles. Insertion is not
an absolute eriterion, as the second dorsal constrictor is inserted

=e |csd.

<

2

= ar?

; iz Fig. 2. Horizontal section through
i gill, Heptanchus maculatus (X 4). ad.,
‘== adduetor of the branchial arch; ¢f.,
NI = afferent artery; br.. branchial ray; csd.,
\ dorsal constrictor musele; eb., epibranch-

ial cartilage; efc.*, fourth efferent col-
lector artery; efc., fifth efferent col-
lector artery; ex. b., extrabranchial car-
tilage; fl. a., anterior gill-filament; fl. p.,
posterior gill-filament; ibd., dorsal inter-
branchial muscle; n. nerve.

CUNT

=

|
= TE NCTE PES :
Za OL f

both on the first and the second arches.
it is not possible to demonstrate a division of the first and second ven-

tral constrictors as clearly as is shown for Acanthias by Marion (p. 9,
fig. 5). The following condition is found in Heptanchus maculatus.
The first and second ventral constrictors appear to be united. The
second ventral constrictor (csv.2) extends from the mandibular sym-

physis to the anterior border of the first gill-slit.

In Heptanchus maculatus

The fibers of both

156 University of California Publications in Zoology (Vou. 18

sides have their origin from a band of connective tissue extending
from the pectoral girdle to the mandibular symphysis. It is broad
near the girdle but narrows rapidly forming a triangular ventral
covering for the coaracoarcuales communes. From this it continues
forward as a narrow strip from which the anterior part of the second
ventral constrictor takes its origin. Anteriorly this muscle is covered
by the first ventral constrictor, a thin layer of fibers lying directly
under the skin and being continuous from one ramus of the mandible
to the other. This, the first ventral constrictor, cannot be clearly
separated from the second. It is inserted on the inner side of the
ramus of the mandible. The anterior part of the second dorsal con-
strictor is inserted along the middle third of the ceratohyoid cartilage ;
the posterior part is continuous with the corresponding dorsal con-
strictor. In passing over the median cartilaginous branchial rays
the muscle forms a tendinous aponeurosis.

Ventral constrictors®* (esv..*) have their origins continuously
along the edge of the triangular piece of connective tissue which
covers the coracoarcuales communes. They pass between the gill-
slits and continue as the fibers of the corresponding dorsal parts.

3. Interbranchials. The interbranchial muscles are so intimately
connected with the dorsal and ventral constrictors that they are in
fact parts of the same muscles. The fibers (ibd., fig. 2) are parallel
with and anteriorly continuous with the constrictors (csd.), and lie
just in front of and against the cartilaginous branchial rays. They
are present in the six holobranchs, but an interbranchial is absent from
the hyoidean demibranch. Their function is to draw the branchial
rays together and constrict the gill-pockets.

For convenience of description they may be divided into dorsal
and ventral parts, corresponding to the constrictors which have been
similarly grouped. The origin of the dorsal parts is in the connective
tissue of the trapezius and dorsal longitudinal muscles anteriorly con-
tinuous with the origin of the corresponding dorsal constrictors. They
are attached to the dorsal extrabranchial cartilages which serve to
hold the muscles in place. The anterior fibers are inserted along the
entire dorsal edge of the epibranchial cartilage from the insertion of
the lateral interarcuales to the angle between the epibranchial and
ceratobranchial segments of the branchial arches. The outer or more
posterior fibers continue into the corresponding ventral part. The
ventral parts (7bv.*°, fig. 4) have their origin in the connective tissue
dorsal and lateral to the coracoarcuales communes. The posterior

1918] Davidson: The Musculature of Heptanchus maculatus al

Or

ventral fibers are continuous with the dorsal part of the correspond-
ing muscle. They are attached to and held in place by the ventral
extrabranchial cartilages. The remaining part, which is anterior,
is inserted along the posterior edge of the. ceratobranchial from the
epibranchial to the hypobranchial segments. The first to the fifth pass
through the first five of the coracobranchiales muscles as described
below. The sixth interbranchial passes between the sixth and seventh
coracobranchiales.

4. Trapezius (tr., fig. 1). The trapezius les between the dorsal
longitudinal muscles and the dorsal constrictors, and is partly covered
by the latter. It arises from the fascia of the dorsal longitudinal
muscles, runs ventrally and posteriorly, and is inserted in two parts.
The ventral part, the origin of which is anterior, is inserted on the
epibranchial segment of the degenerate seventh branchial arch. The
remainder of the fibers have the same direction and are inserted
anteriorly on the pectoral girdle along most of the scapular part. The
trapezius raises the shoulder girdle and draws it forward.

5. Levator labialis superioris (Us., fig. 1). Vetter (1874, p. 448)
classifies this muscle in Acanthias vulgaris with the adductors, but
Marion (1905, p. 21) basing his judgment on Vetter’s description places
it with the constrictors. In Heptanchus cinereus, according to Vetter,
this muscle is absent. In Acanthias (Marion, 1905, p. 21 and Vetter,
1874, p. 420) there is a single pair of muscles, while in the skate (Ties-
ing, 1896, p. 85) the muscle is differentiated into four or five parts.
In Heptanchus maculatus the levator labialis superioris includes two
distinet parts. The first corresponds to the first levator labialis of the
skate or to the whole muscle as described for Acanthias, although the
two are not the same in origin. It is a small somewhat flattened band
having its origin on the inner side of the antorbital process (a. pr.).
Its fibers run posteriorly and outward, cross the angle of the jaws, and
continue as a fibrous band of tissue which separates the dorsal and
ventral parts of the adductor mandibulae. The second probably cor-
responds to the second muscle as deseribed for Raia by Marion (1905,
p. 22). Its origin is on the cranium just anterior to the preorbital
process, and in the region of the nasal capsule, by a wide band of
rather soft tendinous tissue. This .continues posteriorly below the
eye where it joins similar tissue which surrounds the eye and then
crosses the adductor mandibulae. At its posterior end this tendon
passes inward and by a short muscular part, is inserted on the quad-
rate and mandible at the place of their union.

158 University of California Publications in Zoology — | Vou. 18

Il. INTERARCUALES (fig. 3). The interarecuales, the muscles of the
upper segments of the gill-arches, comprise two systems, of which one
is dorsal, and the other more lateral. The first is made up of five,
the second of six similar muscles. Their function is to draw forward
the segment of the arch upon which they are inserted.

1. Dorsal system. The dorsal interareuales (ia.d.*-°) are similar
in origin and insertion. They have their origin posteriorly on the
middle half of the first to the fifth pharyngobranchial cartilages respec-
tively and their fibers pass posteriorly and medially to be inserted on
the anterior border of the succeeding pharyngobranchial segment. The
muscles of this series decrease slightly in size from anterior to posterior
as do also the pharyngobranchial segments of the arches.

Fig. 3. Interarcuales and subspinalis muscles, Heptanchus maculatus, dorsal
view (X 1%). eb.'-’, first to seventh epibranchial cartilages; ia. d.-°, first to
fifth dorsal interarcuales; ia. /.‘°, first to sixth lateral interarcuales; pb.*°, first
to sixth pharyngobranchial cartilages; s.sp., subspinalis muscle.

2. Lateral system. The lateral interarcuales (7a. 1.*~°, fig. 3) are
external to the series of muscles described above. These muscles
decrease in size posteriorly and are similar except in the case of the
sixth. The first may be described as typical. The greater part of its
fibers arise posteriorly from the external part of the first pharyngo-
branchial segment. The remaining fibers have their origin anteriorly
and dorsally from the middle part of the second pharyngobranchial
cartilage. These unite and continue laterally to be inserted dorsally
on the posterior edge of the first epibranchial cartilage. The line of
insertion is continuous with that of the dorsal part of the inter-
branchial muscle. In the seventh arch there is no pharyngobranchial
segment, and the sixth muscle of the lateral series originates by a

1918] Davidson: The Musculature of Heptanchus maculatus 159

single head from the dorsal end of the seventh epibranchial, and from
the sixth pharyngobranchial as in the case of the others of the series.
The two cartilages are closely articulated by connective tissue and
the origin of this muscle is continuous. The insertion is on the sixth
epibranchial as in the case of the others of this series.

III. Supsprvauis (s. sp., fig. 3). Anterior to each series of dorsal
interarcuales is a single muscle, the subspinalis (Vetter, 1874, p. 444).
Marion (1905, p. 24) in disagreement with Vetter who considers this
muscle as belonging to a distinct group, considers it as the most ante-
rior dorsal interarcualis. Its origin, insertion, and occurrence, how-
ever, do not agree with the dorsal interareual series and it seems advis-
able here to describe it separately as the subspinalis muscle.

It has a broad origin ventrally from the posterior part of the
cranium, the vertebral column near the cranium and from the ventral
fascia of the dorsal longitudinal muscles. It decreases in size abruptly
and is inserted by two tendons, the larger on the median end of the
first pharyngobranchial dorsally, and the smaller similarly on the
second.

IV. Appuctrors. The adductors form a series of flexors for the
dorsal and ventral parts of the visceral arches, except in case of
the hyoid, on which the muscle is lacking. This is probably due to the
reduction of the hyoid arch and to its dependenee on the first or mandi-
bular arch. These muscles are very small except in the case of the first
which in correlation with the great use of the mandibular arch is
enormously developed.

1. Adductor mandibulae. The adductor mandibulae (a. md., fig.
1), the adductor of the first visceral arch, is very much larger and
more specialized than the other members of this series. It appears
as a simple muscle having its origin externally on the quadrate region
of the upper jaw, and its insertion similarly on the mandible. This is
the case, however, with only a small part of the muscle, the deeper
posterior part which comprises less than one-third of the whole muscle.
This small part corresponds closely to the adductors of the succeeding
arches. The posterior superficial fibers have their origin on the quad-
rate, but insert on the tendinous envelope covering the ventral part
of the adductor. The remainder, which is by far the greater part of
the muscle, is divided into dorsal and ventral parts by the membranous
posterior continuation of the first part of the levator labialis superioris.
The dorsal division has its origin on the quadrate portion of the upper
jaw ; its direction is ventral and slightly anterior, and its insertion is

160 University of California Publications in Zoology [ Vor. 18

on the dorsal side of the membranous posterior continuation of the
levator labialis superioris. The ventral part has its origin on the
ventral side of the same membrane; its direction is the same as in the
ease of the dorsal fibers and it is inserted on the posterior outer sur-
face of the mandible.

Fig. 4. Hypobranchial muscles, Heptanchus maculatus, ventral view (X 1).
bh., basihyoid cartilage; c.ar., coracoarcuales muscle; cb.', first ceratobranchial
cartilage; c.br.~“‘, first to seventh coracobranchiales muscles; ch., ceratohyoid
cartilage; c.hy., coracohyoideus muscle; co., coracoid cartilage; ce. md., coraco-
mandibularis muscle; ibv.'-*, first to sixth ventral interbranchial muscles; md.,
mandibular cartilage.

2. Adductor arcus branchialis. An adductor, as mentioned before,
is absent from the hyoid arch. The dorsal and ventral parts of each
of the branchial arches (ad., fig. 2) are drawn together by an adductor
areus branchialis which extends from the epibranchial to the cerato-
branchial segments of each arch. The adductors are small and hinge-
like and completely fill the angle between the segments. Their origin

te

1918] Davidson: The Musculature of Heptanchus maculatus 161

is internally in a groove on the distal third of the epibranchial segment
and they are inserted similarly on the proximal part of the cerato-
branchial segment of each arch. Their contraction flattens the
branchial region.

V. HyposraNcHIALs (fig. 4). The hypobranchial or ventral longi-
tudinal muscles le on the ventral side anterior to the pectoral girdle.
They are thick and solid and their shape is correlated with the shape
of the body. They include the coracoarcuales communes, a pair of
muscles extending forward from the pectoral girdle halfway to the
mandibular symphysis; the coracomandibularis, a median ventral
unpaired muscle; the coracohyoideus, a pair apparently continuous
anteriorly with the coracoarculaes; and the coracobranchiales, inelud-
ing seven pairs of flat muscles extending to the gill-arches. This
group of muscles has its origin on the coracoid portion of the scapula
and from the connective tissue forming the floor of the pericardial
cavity which fascia is attached to the coracoid.

1. Coracoarcuales communes (c. ar.). The coracoarcuales muscles
le directly under the integument just anterior to the pectoral girdle.
At their origin they are quite broad but they rapidly decrease in size
anteriorly. Several myosepta may be seen to cross each of these
muscles and give to them the same appearance as the musculature of
the body. Their origin is from the anterior surface of the coracoid.
The median fibers are inserted in the strong membrane which forms
the floor of the pericardial cavity, while the lateral fibers are con-
tinued forward and are inserted in the fascia in which the cora-
cohyoideus muscles have their origin.

2. Coracomandibularis (c.md.). The eoracomandibularis is an
unpaired muscle lying dorsal to the first and second ventral con-
strictors. Its origin is in the fascia dorsal to and between the anterior
part of the coracoarcuales. At its origin it is laterally compressed,
but immediately becomes rounded and is inserted ventrally on the
posterior edge of the mandible, extending on either side of the
symphysis.

3. Coracohyoideus (c. hy.). The ecoraecohyoideus muscles are the
largest of the ventral longitudinal group. They are paired and are
just dorsal to the coracomandibularis. The coracohyoideus muscles
are a direct anterior continuation of the coracoarcuales. Their origin
is from the fascia in which the latter insert. The more dorsal fibers
take origin in the fascia between the coracohyoideus and coraco-
branchiales. The muscles are broad and thick and uniform in size

162 University of California Publications in Zoologr [ Vou. 18
| gy

except for a slight decrease anteriorly. They are inserted ventrally
on the anterior part of the copula of the hyoid arch. A few of the
more lateral fibers are inserted by tendinous tissue, in the tissue
joining the copula and ceratohyoid.

4. Coracobranchiales (c. br‘, fig. 4). The coracobranchiales are
the most internal or dorsal of the ventral longitudinal muscles. They
include seven pairs which form an almost solid wall along the sides
of the pericardial cavity. The first has its origin in the connective
tissue directly over and attached to the coracohyoideus muscles. The
origins of the second to the sixth coracobranchiales are in the strong
connective tissue just dorsal to the coracoarcuales. The anterior part
of the origin of the seventh is continuous with the origin of the sixth,
while the posterior part has its origin on the pectoral girdle, just
laterad of the origin of the coracoarcuales. It extends along about
one-fourth of the ventral part of the pectoral girdle. Near their
origin these muscles form an almost continuous sheet, but they are
separated toward their insertions by the afferent arteries. The first
to the fifth are also divided from their origin about two-thirds of
the way to their insertions by the anterior parts of the ventral inter-
branchial muscles. The sixth and seventh coracobranchiales are
separated by the sixth interbranchial.

The first coracobranchialis passes anteriorly and dorsally and is
inserted on the posterior edge of the basihyoid. The second to the
sixth are inserted posteriorly on the hypobranchial segments of the
corresponding branchial arches, while the greater part of the seventh
is inserted on the ceratobranchial of the last gill-arch. The insertion
of the seventh extends ventrally throughout the entire length of the
segment. The most anterior fibers, however, are inserted on the ante-
rior edge of the posterior median piece. The hypobranchial segment
of the seventh arch is absent or fused with the basal piece.

MuscuLaTuRE ASSOCIATED WITH THE ORGANS OF SPECIAL SENSE

In this division are located the muscles of the eye and of the organ
located in the parietal fossa. The eyelids of Heptanchus are mem-
branous and consequently musculature is not developed in them.

I. Eyc-muscles (fig. 5). The six muscles of the eye-socket are
divided into two groups. The first or oblique group is placed ante-
riorly and consists of two muscles, the superior (s.o0.) and inferior
oblique (7.0.). These two muscles extend from the anterior part
of the orbit outward and backward and are inserted on the eyeball.

1918] Davidson: The Musculature of Heptanchus maculatus 163

The second or rectus group consists of four muscles which originate
from the posterior part of the orbit at the base of the optie pedicel.
The dorsal member of this group is known as the superior rectus
(s. r.), the ventral as the inferior rectus (7. 7.), the anterior and
posterior as anterior (a.7.) and posterior recti (p.r.) respectively.
They pass outward and forward and are inserted on the eyeball in
positions according to their naming. The function of the eye-muscles
is to turn the eyeball in the orbit.

Il. Muscles of the Parietal Fossa (fig. 6). In connection with a
small shield-shaped organ present in the parietal fossa of Heptanchus

Fig. 5 Fig. 6

Fig. 5. Eye-muscles, Heptanchus maculatus, dorsal view (X 1). ar.,
anterior rectus muscle; 7. 0., inferior oblique muscle; 7. 7., inferior rectus muscle;
n. II, optic nerve; 0. p., optie pedicel; p.7., posterior rectus muscle; s. 0., superior
oblique muscle; s.7., superior rectus muscle.

Fig. 6. Organ over parietal fossa, Heptanchus maculatus, dorsal view. (X 3).
e.d., endolymphatie duct; 0., organ in fossa; p.m., parietal muscle.

maculatus, is a pair of small short muscles, the parietal muscles
(p.m.). They have their origin dorsally on the cranium and the
anterior part of the dorsal longitudinal muscles, just posterior to the
parietal fossa. Their course is anterior and medial and they are
inserted postero-laterally on the parietal organ. It seems possible
that these muscles constrict this sac-like organ.

APPENDICULAR MUSCULATURE
There are two types of fins found in the sharks, paired and un-
paired. The paired fins include the pectorals and pelvies, the unpaired
the dorsal, anal, and the caudal. Their musclature is similar and

164 University of California Publications in Zoology | Vou. 18

quite simple except in the case of the pelvic fin of the male, where
an elaborate system of muscles is developed in connection with the
clasper. In all except the anal and caudal fins the muscles are differen-
tiated into radials.

MUSCLES OF THE PAIRED FINS

The radials of the pectoral fin (ra., fig. 7) form a dorsal and a
ventral series. Dorsally they take origin posteriorly and laterally
from the seapular portion of the pectoral girdle, from the pro- and
mesopterygia, and from a band of tendinous connective tissue along

Fig. 7. Left pectoral fin, Heptanchus maculatus, lateral view (X %). co.,
coracoid cartilage; sc., scapula; ra.d., dorsal radial muscles; ra.v., ventral
radial muscles.

the posterior dorsal edge of the fin. Deeper fibers have their origin
dorsally along the metapterygium. The origin of the fibers is not
restricted to the proximal cartilages, but extends over the entire dorsal
surface of the cartilaginous radials of the fin-skeleton. The muscle
fibers making up the radials are short and do not extend the entire
length of the muscles. Their direction is outward and distal. They
insert in the connective tissue which covers each radial muscle. This
tissue is tendinous and is continuous with the dermal fin rays. The
radials number about thirty-two including the small posterior parts
which are not very distinctly separated.

In the ventral series about twenty-six distinet radial muscles may

1918] Davidson: The Musculature of Heptanchus maculatus 165

be counted, although the anterior part here is not clearly divided.
They have their origin on the posterior side of the coracoid portion
of the pectoral girdle, on the pro-, meso-, and metapterygia and on
the cartilaginous fin-rays. Their direction is the same as in the dorsal
series and they are inserted in the connective tissue which is continuous
with the ventral dermal fin-rays.

The pelvic fins are located ventrally, one on each side of the
external opening of the cloaca. In the female the musculature is
quite simple, consisting of a dorsal and ventral series of radials. In
the male the muscles of the clasper are quite complicated. Krall
(1908) deseribed these muscles for Hexanchus. The muscles are
similar to those of Heptanchus, but the terminal cartilages described
have not been found in Heptanchus maculatus. This may be due to
the immaturity of the specimens studied. The naming of the muscles
was taken from Goodey (1910) and Huber (1901).

In the female the dorsal radials of the pelvie fin number twenty-
four. Their origin is double, from the ecnnective tissue of the ventral
body muscles and from the fin-skeleton. The direction of the muscles
is outward and posterior. They insert in the connective tissues as do
the radials of the pectoral fin. Ventrally there are twenty-six radials.
Their origin is on the girdle, in the connective tissue posterior to the
girdle, and on the entire cartilaginous skeleton. The insertion is the
same as in the dorsals.

The radials of the pelvic fin of the male (fig. 9) are similar to
those of the female. Dorsally in a large specimen they numbered
twenty-one and ventrally twenty-three. Besides the usual dorsal
radials there is, in the male, a posterior mass of muscle having its
origin in the fascia of the ventral longitudinal muscles. This passes
almost directly posterior where it spreads out and is continuous with
the posterior dermal fin-rays which fold around the clasper.

The musculature of the clasper includes six muscles, an adductor,
two flexors, a dilator, a compressor, and the sac muscle. In all the
origin is proximal and the insertion distal.

Adductor (ad., fig. 9). The adductor is a specialized part of the
ventral musculature of the pelvic fin. It has its origin on the posterior
border of the pelvie girdle and from the connective tissue posterior
to the girdle. The direction of the fibers is posterior and the insertion
is medial on the distal end of the basipterygium (see ba. p.. fig. 8).

Flexor caternus (f.e.). The flexor externus has its origin along
the middle third of the inner edge of the basipterygium. Its course

166 University of California Publications in Zoology | Vou. 18

is posterior and medial. It is inserted along the inner side of the beta
cartilage (B).

Flexor internus (f. 7). The flexor internus takes origin along
the inner edge of the basipterygium, just under the externus and the
inner side of the beta cartilage, and under the insertion of the
externus. Its direction is posterior and medial and it is inserted on
the inner side of the proximal end of the basal piece (ba.).

Fig. 8 Fig. 9

Fig. 8. Skeleton of male pelvie fin, Heptanchus maculatus, dorsal view
(xX 1). 8B., the beta cartilage; b.-°, connecting segments; ba., basal piece; ba. p.,
basipterygium; pl., pelvie girdle; ra., radial cartilages.

Fig. 9. Musculature of male pelvic fin, Heptanchus maculatus, dorsal view
(X 3%). ad., adductor muscle; cp., compressor; dl., dilator; f. e., flexor externus;
f.i., flexor internus; pl., pelvic girdle; ra., radial muscles; s.m., muscle of sac.

Dilator (dl.). The dilator has its origin on the proximal end of
the basal cartilage (ba.) under the beta cartilage. It is inserted in
the heavy connective tissue covering the basal cartilage distally, form-
ing the inner lip of the groove.

Sac. muscle (s. m.). The sae muscle arises on the connecting seg-
ments (b' and b?) and on the outer side of the proximal end of the
basal cartilage. The dorsal fibers are inserted along the inner side of

1918] Davidson: The Musculature of Heptanchus maculatus 167

a long curved radial which comes close to the clasper. The ventral
fibers form the wall of the muscular sac. Some of these are inserted
along the opposite side of the same radial, while the others continue as
tendinous tissue and are inserted distally on the basal cartilage to
form the outer lip of the groove.

Compressor (cp.). The compressor has its origin laterally from
the beta cartilage (8). Its direction is posterior and lateral and it is
inserted on the most posterior radial cartilage.

MUSCLES OF THE UNPAIRED FINS

The radials of the dorsal fin are about nineteen in number. Their
origin is in the connective tissue of the dorsal longitudinal muscles
and on the fin-skeleton as in the other radials deseribed. They are
inserted in the connective tissue sheaths which continue distally into
the dermal fin-rays.

In the anal fin, which is on the mid-ventral line and posterior to
the cloaca, the muscle is not differentiated into radials, but appears as
an individual mass. The origin is from the connective tissue of the
ventral longitudinal muscles and the fin-skeleton. The insertion is in
the connective tissue sheath similar to that of the radials of the dorsal
fin.

The spinal column continues into the upper lobe of the caudal fin,
making the posterior body musculature the main part of the muscula-
ture of the caudal fin. The ventral musculature of the caudal fin is
similar to that of the anal. It extends from the anterior extremity
of the fin almost to the tip of the tail. Its origin is in the fascia of
the ventral body muscles and from the fin-skeleton. Its fibers are
inserted in the connective tissue covering, which is continuous with
the dermal fin-rays.

MUSCULATURE OF THE TRUNK

Johannes Miiller in 1834 described the trunk musculature of elas-
mobranchs as divided by the lateral septum into a dorsal and a ventral
part. A. Schneider also distinguishes a dorsal and ventral division
but describes layer-formation and the presence of a rectus muscle.
Humphry (1872) working on Mustelus, found that this division into
dorsal and ventral parts separated by the lateral septum, existed in
all forms. Each of these parts he again divided into two parts, the
dorsal into the medio-dorsal and latero-dorsal and the ventral into
the latero-ventral and medio-ventral parts. Humphry describes the

168 University of California Publications in Zoology — [Vou. 18

latero-ventral as having two layers. Maurer (1912) in working on
the trunk musculature of a number of selachians finds that layer-
formation occurs in Mustelus, but not in Scyllium, Spinax, Acanthias,
and others.

In Heptanchus maculatus the body musculature (figs. 10, 11, 12)
is divided by the lateral septum into dorsal and ventral parts. These

Fig. 10. Cross section in trunk region, Heptanchus maculatus (X 7).
b.c., body eavity; l., lateral muscle bundle; /a.v., lateral vein; l.d., latero-
dorsal muscle bundle; 1. 1., lateral line; I. v., latero-ventral muscle bundle; m. d.,
medio-dorsal muscle bundle; m.v., medio-ventral muscle bundle.

longitudinal muscles extend from the cranium to the tip of the tail.
Dorsal to the lateral septum there are three muscle bundles, the lateral,
latero-dorsal, and medio-dorsal. Ventral to the septum are the latero-
and medio-ventral parts. The dorsal part is attached anteriorly to
the cranium and to the pectoral girdle, the ventral part to the pectoral
girdle. The hypobranchial muscles previously described form an
anterior ventral specialization of these latter muscles. The longi-

1918] Davidson: The Musculature of Heptanchus maculatus 169

tudinal bundles are divided by connective tissue septa, the myosepta
into muscle segments, which externally present a zigzag appearance.
At the lateral septum there is a V which points anteriorly. The two
near the median ventral and dorsal lines point posteriorly. The
muscle segments do not extend directly in, as they appear to extern-
ally, but each extends far posteriorly and anteriorly in the direction
of the V’s, giving to each segment an irregular form. The anterior
and posterior extensions of the muscle segments are in the form of

KIS
ne

NG
()
Ph

(0)
Ne)

oD)
1a)

di

WA DSS
Sw)

ioe 1 Fig. 12
Figs. 11 and 12. Cross sections through dorsal fin and caudal regions (X 3%).
c.f., caudal fin; d.f., dorsal fin; l., lateral muscle bundle; I. d., latero-dorsal

bundle; J. 1., lateral line; l. v., latero-ventral bundle; m. d., medio-dorsal bundle;
m.v., medio-ventral bundle.

cones so that in cross section they have the appearance of concentric
rings.

Dorsally the musculature is the same in the tail and in the trunk
except for a difference in the sharpness of the angles of the V’s. The
ventral musculature shows a much more extensive change in the trunk.
The voluminous organs of the body cavity greatly effect the muscles
of the body wall, causing them to form a very thin layer. The V’s
are not sharp and the connective tissue septa pass more directly
inward, forming no cones. This greatly changes the appearance of a
cross section, since in it no concentric rings of muscle are formed.

170 University of California Publications in Zoology —[Vou. 18

LITERATURE CITED
DANIEL, J. F.
1916. The anatomy of Heptanchus maculatus. Univ. Calif. Publ. Zool., 16,
349-370, pls. 27-29, 8 figs. in text.
GoopEy, T.
1910. <A contribution to the skeletal anatomy of the frilled shark, Chlamy-
doselachus anguineus Gar. Proc. Zool. Soc., London, 1910, 540—
571, pls. 42-46.

GoopRIcH, E. 8.

1906. Notes on the development, structure and origin of the median and
paired fins of fish. Quart. Jour. Micr. Sci., 50, 333-376, pls. 10—
14, 1 fig. in text.

HUuBER, O.

1901. Die Kopulationsglieder der Selachier. Zeitsch. f. wiss. Zool., 70,

pls. 27-28, 12 figs. in text.
HuMPHREY, G. M.

1872. The museles of the smooth dogfish (Mustelus laevis). Jour. Anat.

and Physiol., 6, 271-278, pl. 13.
KRALL, A.

1908. Die minnliche Beckenflosse von Hexanchus griseus M. u. H. Ein
Beitrag zur Kenntnis der Copulationsorgane der Selachier und
deren Herkunft. Morph. Jahrb., 37, 529-585, pls. 12-13, 17 figs.
in text.

Marion, G. E.

1905. Mandibular and pharyngeal muscles of Acanthias and Raia. Am.

Nat., 39, 891-924, 15 figs. in text.
MAURER, F.

1912. Die ventrale Rumpfmuskulatur der Fische. (Selachier, Ganoiden,
Teleostier, Crossopterygier, Dipnoer). Jena. Zeitsch., 49, 1-118,
pls. 1-8, 18 figs. in text.

MULLER, E.

1909. Die Brustflosse der Selachier. Anat. Hefte, 39, 469-601, 62 figs. in

text.
RuGeE, G.

1897. Ueber das peripherische Gebiet des Nervus facialis bei Wirbelthieren.

Festsch. f. Gegenbaur, 3, 195-348, 76 figs. in text.

TIESING, B.
1896. Ein Beitrag zur Kenntnis der Augen-, Kiefer- und Kiemen-mus-
culatur der Haie und Rochen. Jena. Zeitsch., 30, 75-126, pls. 5-7.

VETTER, B.
1874. Untersuchung zur vergleichenden Anatomie der Kiemen- und Kiefer-
musculatur der Fische. Jena. Zeitsch.. 8. 405-458. nls. 14-15.

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Vol.17. 1

24

" 2,

8

s

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Notes on the Tintinnoina. 1. On the: Probable Origin of Dictyocysta tiara
Haeckel. 2. On Petalotricha entzi, sp. nov., by Charles Atwood Kofoid,
“Pp. 63-69, 8 figures in text. December, 1915 EP SLA Sete BO NOEL REM

pea and Multiple Fission in examitus; by Olive Swezy.° Pp. 71-88,
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On a New Trichomonad Flagellate, Trichomitus parvus, from the Intestine

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-.. Nos..6and 7:in one cover. December,1915°..
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Three New Helices from California, by S. Stillman. Berry. Pp. 107- 111,
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the Nests of the Wood Rat Neotoma fuscipes, by Charles Atwood Kofoid

and Irene McCulloch: Pp. 113-126, plates 14-15.. February, 1916 ...:..........
The Genera Monocercomonas and Poli ymastia, by Olive Swezy. Pp. 127-138,
MlgtescLG-T7o-s Sewraary,, TO1G-ox. 3 Soo ee
Notes on the Spiny Lobster (Panulirus interruptus) of the California Coast,
by Bennet. M. Allen, Pp. 139-152, 2 figures in text. March, 1916.20.00.
Notes on the Marine Fishes of California, by Carl L. ‘Hubbs. Pp. 153-169,
plates* 18-20 Marghs 199622 6 ee eR a Se ae ES a
The Feeding. Habits and. Food of Pelagic Copepods ‘anak the Question of
“Nutrition by-Organie Substances in Solution in the Water, by Calvin-O.
-Esterly.. Pp..171-184,.2 figures in text.. March, 1916 220.2... Ses east ee aa
The Kinetonucleus of Flagellates and the Binuclear Theory of Hartmann,
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On ‘the Life-History of a Soil Amoeba, by Charlie Woodruft Wilson. Pp.
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Distribution of Land Vertebrates of Southeastern Washington, by Lea
Raymond Dice. Pp. 293-348, plates 24-26. June, 1916 -.002.2.
The Anatomy of Heptanchus maculatus: the Endosxeleton, by J. Frank
Daniel. Pp, 349-370, pls. 27-29, 8 text figures. December, 19167 0.00....0.2
Some Phases of Spermatogenesis in the Mouse, by Harry B. Yocom, Pp.
Sf 1-380s plate--30,<° Panuary; 198 Tak 42 se as eae ees ge aapacey
Specificity in Behavior and the: Relation between Habits in Nature and
Reactions in the Laboratory, by Calvin O. Esterly. Pp. 381-392. March,
RE eo ae ee ee A eae RY eee ee Os as
The Occurretice of a Rhythm in the Geotropism of Two Species of Plank-
ton Copepods when Certain Recurring External Conditions are Absent, by
Calvin: Os-Bsterly, = Pp: 393-400. March) 1917 or es ahaa cate

On Some New Species of Aphroditidae from the Coast of California, by

Christine Essenberg. Pp. 401-480, plates 31-37. March, 1917 -..2...0.2028

by Harold Tupper Mead. Pp. 431-438,.1 text figure. . April, 1947 _.........
Ascidians of the Littoral Zone of Southern California, by William E, Ritter

“and Ruth A. Forsyth. Pp. 439-512, plates 38-46. August, 1917 222...

Diagnoses of Seven. New Mammals: from East-Central California, by Joseph
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Nos: 1 and 2 in one cover, August, 1916 2... 2oocccleece ep ceeceeeedetee ele ennsoenncee

. Spelerpes. platycephalus, a New Alpine Salamander. from the Yosemite

National Park, California, by Charles Lewis Camp. Pp. 11-14. Septem-

Boa 3) ARG RS 1 eA NC i pelle woe epic sa ia as ob epee Wa 5 Meta Cat fae nape li RL er

A New Spamnonitia from the San Joaquin Valley, California, with Notes

‘on Aminospermophilus nelsoni nelsoni Merriam, by Walter P. Taylor. Pp.

15-20; 1 figure in text... October, 1916 o.oo. o occ i pssst ces cet cee cnencsecerepenmeneennee
Habits and Food of the Roadrunner in California, by Harold C. Bryant.
Pp. 21-58, plates 1-4, 2 figures in text. October, 1916-00022... stn
Description of Bufo canorus, a New Toad from the Yosemite National Park,
by Charles Lewis Camp. Pp. 59-62,.4 figures in text. November, 1916._....
The Subspecies of Sceloporus occidentalis, with Description of a New Form
from: the Sierra Nevada and Systematic Notes. on~ Other California
- Lizards, by Charles Lewis Camp. Pp. 63-74, December, 1916 -...:-_.:.......

‘Osteological Relationships of Three Species of Beavers, by F. Harvey

Holden. Pp. 75-114, plates 5-12, 18 text figures, March, 1917 ....:........--.-
. Notes on the Systematic Status of the Toads and Frogs of California, by
Charles Lewis Camp. Pp. 115-125, 3 text figures. February, 1917 .. Secnb cinta

10.

11.

7. The Transmission of Nervous Impulses in Relation to Locomotion in the nS
Earthworm, by John F. Bovard. Pp; 103-134, 14 figures in text. January, p=
2 C1) ih. Berar dln re SER RE tan Mey age oO eats Bhs Henke. Veneer ap serail, OE Grey mur geht A *

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A Distributional List of the Amphibians and Reptiles of Saltdecute: be

Joseph Grinnell and Charles alpad Camp. Pp. 127-208, 14 figures in text.
Oily? TOUT: oe earns ee ew Miers Ce eee we

A Study of the Races of the White-Fronted Goose (Aner Gibifronsy. Occur-_
ring in California, by H. 8. Swarth and Harold C, Bryant. Pp. 209° 222, ee

2 figures in text, plate: 133 , October; 1927230 ea,

A Synopsis of the Bats of California, by Hilda Wood Grinnell. Pp 223-404,

plates 14-24, 24 text figures. January. 31,1918. :...... r yeataBatT eS ua Ay i < e S

The Pacific Coast Jays of the Genus ‘Aphelocoma, by H.S. Swarth. Pp.

405-422, 1 figure in text. February 23, 1918 2.20.

. Mitosis in Giardia Microti, by William C. Boeck. Pp. 1-26, plate as. Octo- S
j od) wiigce) 6210 Be Carica eS ee Ae EP WR ee CR re Manco nails pune eS NERS Ae Sel Sa cae ner AN
. An Unusual Extension of the Distribution of the Shipworm in San’ Fran ss
cisco Bay, California, by Albert L. Barrows. Pp: 27-43. December, 1917.
Description of Some New Species of Polynoidae from the Coast of Cali-. —
fornia, by Christine Essenberg. Pp. 45-60, plates 2-3. October, -1917 ......

. New Species of Amphinomidae from the Pacific Coast, by Christine Essen-

berg. Pp. 61-74, plates 4-5, “October, 1917 2.0. cc. oe ceo cesta

Crithidia Buryophthalmi, sp. nov., from the Hemipteran Bug, Euryophthalmus s
Convivus Stal, by Irene McCulloch. Pp. 75-88, 35 text raja taork Decem-
ga cs glen HS 5 Seren este = cae eo aes apie Enc te i i see ie Sa Bal cor waral AN A ee eee Ls roam ¢

On the Orientation of Hrgthropeis, ‘by Charles Atwood Kofoid and Olive
Swezy. Pp. 89-102, 12 figures in text. December, 1917 -.....-00022. ee

The Function of the Giant Fibers in Earthworms, by J ght F. Bovard. Pp.
185-144,-4- figure in text. = Jannary,. 1918) 5.22 Ske ee hee tte

~A Rapid Method for the Detection of Protozoan Cysts in Mammalian

Faeces, by. William C. Boeck. Pp. 145-149.\- December, 1917 ..20.-0...2

. The Musculature of Heptanchus maculatus, by Pirie Davidson... Pp. 151- 170, We
42 firnres in. text: Warch;- 1918 easy ee ae sagt anre tea pactunce ated ac

The Factors Controlling the Distribution of the Polynoidae of the Pacific

Coast of North America, by Christine Essenb 8: Pp. 171-238, plates 6-8, =

2 fistires<in. text, ~ SWArChe 74 O26. oe ec os Sa ean sa dapat eeu tees eae

. Differentials in Behavior of the Two Generations of Salpa Democratica
Relative to the Temperature of the Sea. Pp. 239-298, plates: 9-11, 1 fig:
pore. Ui cteRt. arch s AOS esse ie Se ac sateen guanine ce taeede ett ae head asdusas openon noes

2.00

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: es 28
Se Es ZOOLOGY :
Vol. 18, No. 11, pp, 171-238, plates 6-8, 2 figures in text March.8, 1918 —

THE FACTORS CONTROLLING THE DISTRIBU-
TION OF THE POLYNOIDAE OF THE PACIFIC
COAST OF NORTH AMERICA

BY

‘CHRISTINE ESSENBERG

UNIVERSITY OF CALIFORNIA PRESS
| BERKELEY

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i

UNIVERSITY OF CALIFORNIA PUBLICATIONS
IN

ZOOLOGY
Vol. 18, No. 11, pp. 171-238, plates 6-8, 2 figures in text March 8, 1918

THE FACTORS CONTROLLING THE DISTRIBU-
TION OF THE POLYNOIDAE OF THE PACIFIC
COAST OF NORTH AMERICA

BY
CHRISTINE ESSENBERG

CONTENTS
PAGE
Joho UMTS OY UITVG) SD) ts Zeke hl Ae eae a a AY Ry ARBs al ee ld 17
ENC RmONe teamienitigy corm 4 Akt 2 nl ib, 1 he Ry ee een 173
C2 Polynoidae and their peneraldistribution uu). 220). 00 0 ee 174
Bee Oromia Gd str NOU LON oceans sate Ae to I 174
i Eaniwmnen tical das ten ONtlON snc acon cet es eee 179
meat LO AIS Cl entre ct 5 Aeon oS oe a Me ee 182
Za EP PSE BEDS DECOR, es. ce 2 Boe ke eee eas vn 183
Dy Hactors controlling distribution. 20.22). ke WN
I. Temperature in relation to depth and latitude 0.0 191
II. Temperature as factor controlling distribution 00 200
hike Rolexot currents imvdistribution is... 2.4503 eee ee 206
PRU Reena oe iY cae th le eh a 208
V.\Chemical composition of water 2.0.2.2. eccue Be . 209
Mi Bead Habitsiand mode of lite: :. 02 210
EDIT TECH GCI Sy, Mid A ee ee Oe Pee mn BRERA RIND ee) Dy hE ELE) 10 ialg 213
Bee eoralciscUSSiOM), 26 tae MR toe et ca ie ee) a eee ye 221
io) (SUITE A ie EASA eet ae, SOT Uk los 229
Sth SUNS Sen ATS Or 0 | IS en AS EWP ee ACO ORES 9 ay) 231
Ie, Pre planiation Oly plates es ee ten kat tn. Se, See Oe ge St 234

A. INTRODUCTION

Polychaetous annelids date back at least to the Cambrian era, fossil
annelids representing several groups, some of which are similar to
modern annelids, having been found in the mid-Cambrian rocks (Wal-
eott, 1911). The geological studies of the distribution of annelids seem

2 University of California Publications in Zoology [Vou. 18

to point to the conclusion that in Cambrian times the annelids had
entered all the life zones of the oceanic waters except possibly the
abyssal, and that the principal divisions of the annelids were clearly
established in pre-Cambrian times (Walcott, 1911; Osborn, 1917).

The distribution of the annelids has received careful attention
only in recent years. Michael Sars (1850), one of the first imvesti-
gators of oceanic fauna, published the results of dredgings along the
coasts of Norway, including in his report the annelids collected. The
greatest depth to which his dredging extended, however, was only
300 fathoms. Claparéde (1875) briefly described the annelids col-
lected by the ‘‘Lightning’’ Expedition from depths to 650 fathoms.
Ehlers’ work (1875) on the distribution of Annelida, collected by the
‘‘Porcupine’’ Expedition, is of greater importance because that was
the first expedition in which the bathymetric and horizontal distribu-
tion of the annelids was considered on a large scale. The work of
Darboux (1899) on Aphroditidae along the coasts of France and in
the Mediterranean Sea also adds to the knowledge of distribution of
that family of annelids.

The greatest contribution to science in the studies of distribution
of marine life, however, was made by the ‘‘Challenger’’ Expedition
(1872-1876). This ship circumnavigated the globe, its dredging at
various latitudes extending to depths of over 4,000 fathoms. Animals
dredged were grouped and classified by a number of specialists belong-
ing to different nationalities. The lot in annelid studies fell to
McIntosh, who rendered excellent service. In this country the United
States Survey Steamer ‘‘Blake’’ explored the Gulf of Mexico, the
coasts of Florida and the Caribbean Sea. The United States Steamer
‘“ Albatross’’ has been engaged for a number of years in explorations
of the Atlantic coast and the Pacific Ocean. Our knowledge of anne-
lids in this country has been enlarged by the reports of EK. Ehlers,
J. P. Moore and A. Treadwell.

As a result of all these investigations the physical conditions of
the oceans are to some extent known, and enough has been learned
about the distribution of marine life so that questions as to how deep
and how far north or south it extends no longer oceupy the minds
of biologists. It is known that life exists at all depths and in every
latitude. The question that is of interest to every biologist at the
present time is: What is the influence of environment on animal life
in general, and why are certain kinds of animals limited to certain
.areas?

1918 } Essenberg: Distribution of the Polynoidae M3

It has been proved by experimental methods in biological labora-
tories that changes in environment, such as slight variation in tem-
perature, in chemical composition of water, ete., result in external
changes of the animal and often in its death. Loeb (1915), subject-
ing Fundulus eggs to low temperature, produced abnormal and blind
fish embryos, among which the mortality was very great. The eggs
of the same fish when exposed to low temperature for a longer period
were killed. Stockard (1909) treated the eggs of Fundulus with
potassium cyanide, and monsters with a single cyclopean eye and
with the mouth removed from the extreme anterior tip ventrally were
produced. Tower (1906), subjecting the eggs of chrysomelid beetles
to different temperatures, obtained beetles of different color. Beetles
which developed from the eggs that had been subjected to high tem-
perature were of dark color, while those that came from the eggs
subjected to low temperature (0°-5°C) were of a light color. The
mortality of the embryos varied with the period of the exposure to
high or low temperatures and with the age of the eggs and embryos
exposed, the more highly developed eggs and older embryos being
‘the more resistant. Many similar cases may be cited which prove
that changes in environment, either chemical or physical, have marked
effects on animal life. This is especially true of animals in early
stages of development. The above mentioned facts suggest the possi-
bility that similar environmental conditions may have corresponding
effects on the oceanic fauna, and may play an important réle in their
distribution.

The aim of this article is to discuss the factors controlling the
distribution of the Polynoidae. Conclusions are based on the studies
of the material in the Zoological Museum of the University of Cali-
fornia collected by the U. S. S. ‘‘Albatross’’ and private collectors
from the Pacifie coast of North America, in addition to a survey of
the records of other workers on this subject in this region.

B. ACKNOWLEDGMENTS

I take this opportunity to express my sincerest gratitude to Pro-
fessor Charles A. Kofoid at whose suggestion this work was begun,
through whose assistance I have been able to continue it and whose
criticisms have been invaluable. I also wish to express my gratitude
to Dr. Olive Swezy for her valuable suggestions and for the interest
she has taken in my work. I further wish to express my gratitude to
Dr. G. F. MeEwen who kindly computed the temperatures for table 5 °
in this article.

174 University of California Publications in Zoology [Vou 18

C. POLYNOIDAE AND THEIR GENERAL DISTRIBUTION

The Polynoidae, one of the families of the scaly annelids, pass the
first stage of their life as trochophore larvae. The eggs, after leaving
the body cavity of the worm, are attached by a mucous secretion to
each other and to the dorsal surface of the parent’s body beneath the
scales. There they develop until a preoral band of cilia is formed,
when the larvae escape as the well known trochophores swimming
freely near the surface of the water. The larvae finally settle to the
bottom of the ocean, undergoing there further metamorphosis and
assuming gradually the shape of the adult worm. Thus during its
embryonal development, the stage of the greatest susceptibility, the
polynoid is subjected to considerably varied environmental conditions.

Polynoidae as a group are cosmopolitan in their distribution, rang-
ing from the arctic to the equatorial and to the antarctic regions,
inhabiting the littoral as well as the abyssal zones. However, the
same species may not be represented in all of these regions.

I. HorizontTau DISTRIBUTION

On the basis of distribution the Polynoidae may be divided into
two main groups: (1) the cosmopolitan polynoids; and (2) poly-
noids limited to restricted areas. These groups, especially the latter,
may be again separated into a number of subdivisions, according to
the areas they inhabit, as will be shown in the following pages.

Of the fifty-one species of Polynoidae known up to the present
time from the Pacific coast of North America, two species, or about
four per cent, are cosmopolitan. These two species are Harmothoé
imbricata and Lepidonotus squamatus. The former is known to occur
in all European oceanic waters. Marenzeller (1902) describes it from
the coasts of Japan. Other workers record its distribution from Cape
Cod to the St. Lawrence, from Siberia, Greenland, Iceland and from
Seandinavia. Its presence has been recorded in the Okhotsk Sea and
in other parts of the Arctic Ocean. It also occurs in great abundance
along the Pacific coast of North America from Alaska to San Diego,
California.

Lepidonotus squamatus occurs in great abundance in the Atlantic
Ocean along the shores of Great Britain and in Canadian and Ameri-
can waters. It has been found off the Azores at a depth of 450
fathoms (McIntosh, 1900). Although it does not occur in great
abundance along the coast of California, nevertheless, specimens have

1918 | Essenberg: Distribution of the Polynoidae 175

been obtained at different places along the coast from Cape Mendo-
cino on the north to Los Angeles on the south.

Of the forty-nine species of Polynoidae restricted to the waters of
the Pacific coast of North America two species, Halosydna insignis
and Lepidonotus cacloris, have the widest range of distribution of all
the polynoids known on this coast. The distribution of the former is
recorded from Alaska and Puget Sound to Point Conception. So far
as 1s known, however, this species has not been obtained either in the
Arctic Ocean or in tropical regions south of Cape San Lueas. Lepi-
donotus caeloris occurs in great abundance along the coast of Cali-
fornia, from Monterey to Cape Colnett. It is also recorded from the
coasts of Japan and from the waters of Alaska. The remaining forty-
seven non-cosmopolitan species of Polynoidae of this coast may be sub-
divided into definite groups on the basis of their geographical dis-
tribution. Each group belongs to a particular life zone.

The generally recognized life zones on the Pacific coast are: (1)
the tropical zone, extending from the equator to Cape San Lueas; (2)
the north subtropical zone, extending from Cape San Lueas to Point
Conception; (3) the north temperate zone, extending from Point
Conception to Cape Flattery; (4) the lower boreal zone, from Cape
Flattery to the Bering Sea; and (5) the upper boreal zone, from the
Bering Sea northward (Setchell, 1915).

Each zone includes a distinct group of Polynoidae. Since there
are but very few strictly upper boreal or tropical species of Poly-
noidae represented in the annelid collection of the University of Calli-
fornia, these two zones are of less importance in connection with this
work and do not enter into the discussion on the following pages.

The following table (1) shows the geographical distribution of
the Polynoidae. Certain species may be grouped as strictly subboreal,
others as temperate, and still others as subtropical, although there are
a few exceptions. Occasionally a species may be found in two adjacent
zones, and again species may be found occupying very limited areas,
not even extending throughout one entire zone included between the
points given. It should be remembered that the distribution of some
of the species is as vet inadequately known.

176 University of Califorma Publications in Zoology

TABLE 1*

[ Vou. 18

HorIzONTAL DISTRIBUTION OF POLYNOIDAE

Species
Gattyana cirrosa

Gattyana ciliata

Gattyana amundseni
Eunoeé depressa
Harmothoé truncata
Harmothoé foreipata
Hololepida magna
Lagisca multisetosa
Lepidonotus robustus
Polynoé fragilis
Polynoé lordi
Harmothoeé tuta
Melaenis loveni
Harmothoé imbricata
Lepidonotus squamatus
Halosydna insignis
Polynoé spicula,
Harmothoé bonitensis
Harmothoé scriptoria
Harmothoé iphionelloides
Harmothoé crassicirrata
Eunoé barbata

Kunoé caeca

Antinoé macrolepida
Antinoé anoculata
Nemidia microlepida
Harmothoé yokohamiensis
Harmothoé triannulata
Harmothoé multisetosa
Polynoé californica
Harmothoé lamellifera
Harmothoé hirsuta
Harmothoé pacifica
Harmothoé fragilis
Harmothoé tenebricosa
Harmothoé johnsoni
Gattyana senta
Polynoé remigata
Polynoé filamentosa
Polynoé aciculata
Polynoé renotubulata
Halosydna lagunae

Lower

boreal temperate subtropic

Xx

ER DS SCTE OK OE PONS OG Ge EOS

Localities

North North

x s
x A
x
xf
x x
x x
x x
x Z
x
x
x
x
x
x
x ae
x A
x
x x
x? x
x x
x x
as x
2S x
x
x x
D4 x
vs x
7
XK x
: x
x
x
x
x

Other
localities

Greenland, shores of
Norway and around
the shores of Eng-
land

Greenland,
McCormick Bay

Cosmopolitan
Cosmopolitan

Eno-Sima, Japan

*Table 1 shows the horizontal distribution of Polyncidae according to the life zones as |
above indicated. X indicates the presence of the species in the zone.

1918 | Essenberg: Distribution of the Polynoidae 1

~]

=)

TABLE 1—(Continued)

Localities
4 Lower North North Other
Species boreal temperate subtropic localities

Halosydna succiniseta ae a x
Halosydna macrosephala Sy

Halosydna interrupta ze sty s
Lepidosthenia gigas ive oe x
Lepidonotus ecaeloris x x

Harmothoé complanata x ae x

Considering the species with reference to distribution in the wif-
ferent zones we get the results shown in table 2.

As is shown in table 2 there are eleven exclusively subboreal species
of Polynoidae. Four species are common to the lower boreal and north
temperate zones. Of these, Polynoé lordi is more abundant in the
lower boreal zone, occurring very rarely in the northern part of the
north temperate. There are ten exclusively north temperate species,
and eighteen exclusively subtropical species. Polynoé californica
really belongs to the latter zone but occasional specimens of it have
been found in the southern part of the north temperate zone. Four
of the species are found in all zones. Two of these are the cosmopoli-
tans Harmothoé imbricata and Lepidonotus squamatus and the two
others are the American species Halosydna insignis and Lepidonotus
caeloris.

In some eases the individuals of a species are very few in number,
at least in collections, and again many species are abundantly repre-
sented. However, these species are always found in their particular
zones as has been shown before and are limited to very small areas.
Examples of these are Polynoé fragilis and Polynoé lordi. These have
been recorded thus far only from the coastal area included between
Alaska and San Francisco Bay. Harmothoé tuta is seemingly re-
stricted to the northern part of the lower boreal region, its existence
being known only at Puget Sound and Sitka. A great number of
species of Polynoidae inhabiting this coast are limited to the southern
part of the coast of California. Among these are Lepidasthenia gigas,
Polynoé californica and Harmothoé hirsuta. They occupy a compara-
tively small area along the coast from San Pedro to San Diego. A
number of other species, namely, Harmothoé triannulata, Harmothoé
fragilis, Polynoé remigata, and Polynoé filamentosa, have been found
thus far only around the islands west of San Diego. Some of these
species are known to occur only at considerable depths. Areas of
intensive collecting doubtless influence these apparent limitations to
some extent.

[ Vou. 18

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1918 | Essenberg: Distribution of the Polynoidae IS)

Il. BATHYMETRICAL DISTRIBUTION

An attempt is here made to group the Polynoidae according to
their bathymetrical distribution. The different bathymetric groups
although less strictly defined than those of horizontal distribution
(tables 1, 2) are nevertheless recognizable. One difficulty with this
system of bathmetric grouping is that of trying to fit Polynoidae of
the entire coast into groups according to their bathymetric distribu-
tion disregarding their horizontal distribution. Consequently the
results are expected to be less definite on account of the diverse environ-
mental conditions at the different latitudes and at the different depths.
As is shown in table 3, there are very few species that are strictly
limited to one bathymetric zone, but they usually occur in one or more
adjacent zones. On the whole it is found that certain species desig-
nated as littoral may occur in the next greater depth, but as a rule they
are not found in very great depths, while on the other hand species are
found in deep waters which are never found in littoral zones above
one hundred fathoms. Consequently there is sufficient reason for sub-
dividing the species on the basis of their bathymetric distribution into
httoral, sublittoral and deep water species.

WARE oe
BATHYMETRICAL DISTRIBUTION OF THE POLYNOIDAE

Depth in fathoms

Name 0-30 30-100 100-500 500-1000 1000-5000 Exceptional cases
Halosydna insignis x /. ise sees = 291-298 fathoms
off San Nicholas
Island

Halosydna succiniseta x
Eunoé barbata x
EKunoe depressa x

x

Polynoé ealifornica One specimen found

in 90 fathoms deep
Polynoé fragilis

x
Polynoé lordi x
Harmothoé tuta x
Harmothoé hirsuta x
Harmothoé johnsoni x
Harmothoé pacifica x
Harmothoé iphionelloides x

*In table 3 the bathymetrical distribution of the Polynoidae is shown. The depths are
given in five columns, 0-30, 30-100, 100-500, 500—1.000, 1,000—5,000 fathoms. x signifies
the presence of the species in that depth. Species found about and beyond the depth of 100
fathoms are considered in this article as deep water species. Absolute littoral species are
considered those inhabiting the shallow shore waters to the depth of 30 fathoms.

180

Name
Harmothoé complanata
Harmothoé truncata
Harmothoé imbricata
Halosydna lagunae
Polynoé pulchra

Lepidonotus robustus
Lepidonotus squamatyps

Halosydna macrocephala
Harmothoé bonitensis
Harmothoé crassicirrata
Antinoé macrolepida
Harmothoé seriptoria
Harmothoé triannulata
Gattyana senta
Gattyana amundseni

Halosydna interrupta
Hololepida magna
Lepidasthenia gigas
Gattyana ciliata
Nemidia microlepida

Harmothoé yokohamiensis...-

Harmothoé forcipata
Harmothoé fragilis
Polynoé remigata
Polynoé filamentosa
Harmothoé tenebricosa
Polynoé aciculata
Eunoé caeca

Antinoé anoculata
Polynoé renotubulata
Lepidonotus caeloris

Harmothoé lamellifera
Harmothoé multisetosa

Lagiseca rarispina
Gattyana cirrosa
Melaenis loveni

TABLE 3—(Continued)

0-30

x —
x x
x x
x x
x x
x

x

aoe x
x

x

x

x

x

x

x

x

x

x x
x

x x
x =
Xx x

Depth in fathoms

SECS

WKS DR OK EO

2S PS ES eX

x

ore=

Xx

See

University of California Publications in Zoology

30-100 100-500 500-1000 1000-5000

[ Von. 18

,
Exceptional cases

156-162 fathoms
off Santa Catalina

In few cases 12-51
fathoms

Greenland at 16
fathoms depth

One specimen in depth
of 1040-1062
fathoms

One example in 1400
fathoms off Cape
Colnett

One example taken
from 1400 fathoms
depth off Cape
Colnett

Summarizing the species given in the foregoing table, we get the
results shown in table 4.

Distribution of the Polynoidae

Essenberg

1918]

Littoral exclusively
Species

Halosydna insignis
Halosydna californica
Halosydna lagunae
Halosydna succiniseta
Halosydna macrocephala
Eunoé barbata
EKunoé depressa
Harmothoé hirsuta
Harmothoé johnsoni
Harmothoé complanata
Harmothoé iphionelloides
Harmothoé pacifica
Harmothoé tuta
Polynoé fragilis
Polynoé lordi

15 species

TABLE 4*

BATHYMETRICAL DISTRIBUTION OF THE POLYNOIDAE

Sublittoral ex-
clusively

Species
Lepidonotus robustus
Lepidonotus squamatus
Lepidasthenia gigas

Harmothoé crassicirrata

Harmothoé bonitensis
Harmothoé scriptoria
Antinoé macrolepida
Halosydna carinata
Halosydna interrupta
Polynoé spicula

10 species

* Table 4 is a short summary of table 3.

Common to littoral and
sublittoral areas

Species
Polynoé pulchra
Harmothoé imbricata
Harmothoe truneata
Harmothoé scriptoria
Melaenis loveni

oO

species

Exclusively deep
water

Species
Eunoé caeca
Antinoé anoculata
Nemidia microlepida
Harmothoé yokohamiensis
Harmothoé tenebricosa
Harmothoé fragilis
Harmothoé forcipata
Polynoé remigata
Polynoé filamentosa
Polynoé aciculata
Polynoé renotubulata
Hololepida magna
Gattyana ciliata

13 species

Common to sublittoral
and deep water

Species
Harmothoé multisetosa
Harmothoé lamellifera
Harmothoé triannulata
Harmothoe scriptoria
Harmothoé rarispina
Gattyana senta
Gattyana amundseni
Gattyana cirrosa
Lepidonotus caeloris

9 species

182 University of Californa Publications in Zoology ([Vou.18

1. LirroraAL SPECIES

It is a general phenomenon that oceani¢ animals, as far as the num-
ber of individuals is concerned, are more abundant in littoral zones
than in deep water. This is true of Polynoidae, some littoral species
of which are very numerous. This, however, is not true of the number
of genera and species, greater numbers of groups being represented
in deep waters as is shown in table 4, where fifteen species are given
as exclusively littoral. The fifteen littoral species belong to four
genera. There are, moreover, fourteen exclusively deep water species
and seven genera, the species being equal and the genera being almost
double the number of those of the littoral zones. The explanation of
this may be that the littoral zone being the location of greatest abun-
dance of individuals is the center of origin of the Polynoidae and
their center of dispersal.

That the littoral zone is the center of dispersal may be assumed on
the basis that the individuals are very numerous in that zone and that
the species are less varied or more nearly related. On the other
hand the great diversity of species in the deep waters may be attri-
buted to the environmental change and to the sudden shock effect on
the larval stages of the Polynoidae. These changes may be brought
about in larvae that are driven from the shores to the deep waters
undergoing there considerable change in temperature, especially when
they drop to the bottom ; the shock effect of the cold temperature most
probably kills the majority of the larvae and the few survivors that
are able to adapt themselves are physically so changed as to form
new species or even new genera.

Or again, if adult polynoids are driven to depths, they possessing
a greater power of resistance than the larvae, have more chance to
survive but their offspring will undergo a considerable change. In
the first place, the low temperature at the bottom of the ocean would
naturally cause death and abnormalities among the embryonal poly-
noids and when rising to the surface as trochophores they are sub-
ject to a sudden temperature change. The percentage of mortality in
this case would be very great, and abnormalities resulting in con-
spicuous variations would be great. This assumption is based on
laboratory experiments in which similar results may be produeed arti-
ficially by suddenly changing the temperature.

The littoral species most common on this coast occurring in less
than 30 fathoms depth are not strictly confined to that bathymetric

1918] Essenberg: Distribution of the Polynoidae 183

area, but have been frequently found in depths of 100 fathoms or
more. Halosydna insignis has been taken occasionally from a depth
of 200 fathoms. A few specimens of Halosydna californica have been
taken from depths of 90 fathoms. Harmothoé hirsuta, a typical lit-
toral species, has been found occasionally in a depth of 78 fathoms.
Harmothoé imbricata is a cosmopolitan littoral species. It is abun-
dantly represented on this coast, being usually found between tide
marks, but also occurring at various depths, even below 200 fathoms.
The examples found beyond 30 fathoms, however, are comparatively
few, and the species may be designated as a littoral one.

2. DEEP WATER SPECIES

The converse of what has been said of littoral polynoids is also
true of deep sea forms; that is, certain species of Polynoidae are
exclusively inhabitants of deep waters and have seldom, if ever, been
found in shallow waters. As is indicated in table 3, different deep
water species occupy different bathymetric areas. As an example of
such deep water species may be given Lepidasthenia gigas. This poly-
noid is restricted to a comparatively small area on the coast of south-
ern California. It occurs there in great abundance beyond the fifty-
fathom line. The greatest depth, however, from which this species has
been taken is 140 fathoms. This proves it to be a species of a limited
bathymetrieal distribution, inhabiting the sublittoral zones.

Other species again, as Polynoé filamentosa, Antinoé anoculata and
Eunoé caeca, have been reported, up to the present time, only from
depths of 500 to 1,000 fathoms. Still other species, as Halosydna
interrupta, Harmothoé multisetosa, Harmothoé lamellifera, Lepido-
notus caeloris, occur in various depths between 30 and 1,400 fathoms.
Those species again have never been found in the lttoral zone (1-30
fathoms). A number of other species of Polynoidae of this coast
appear to be restricted to definite depths and may be justly con-
sidered as deep water species (table 5). Moreover, individuals of the
same deep water species occupying widely separated geographical
areas occur in the same relative depths, which serves as further evi-
dence that they, under similar conditions of temperature, are deep
water species in any part of the world. As an example may be men-
tioned Lepidonotus caelorus, found off Japan between 63 and 155
fathoms depth; while on this coast examples of it have been taken
from water varying in depth from 30 to 1,400 fathoms. Another

[ Vou. 18

184 University of California Publications in Zoology

example is Harmothoé forcipata. This species has been found near
Eno-Sima, off the coast of Japan, in depths of 100 to 250 fathoms.
Individuals of the same species, however, have been found near the
southern coast of California in various depths from 448 to 600 fathoms.
The cosmopolitan species, Lepidonotus squamatus, is an exception.
The species is known as a littoral form in various parts of the world.
On this coast, however, the species inhabits a depth of 90 to 100

fathoms.

12 to 15 fathoms.

TTABIUE Me

Only in one case has that species been found at a depth of

SHOWING VERTICAL AND HORIZONTAL DISTRIBUTION

Depth
in Tempera-
Name Position fathoms turet Other localities
Lepidonotus robustus Shelikof Strait, Alaska 48-65 10°.8 Locality of one speci-
(on hermit crab) men unknown
Lepidonotus squamatus Point Cavallo 12-15 Everywhere around
Black Point, San Fran- 90-100 British Isles; along
cisco Bay, Monterey the Atlantic coast ;
Bay and Santa Monica from St. Lawrence
. to Cape Cod, Mass.
Lepidonotus squamatus Monterey Bay, Calif. 90-100 Syl
Lepidonotus squamatus Santa Monica, Calif. 13°—20°
Lepidonotus squamatus Santa Moniea, Calif. 450 Off Azores, 450
fathoms
Lepidonotus squamatus Santa Moniea, Calif. Greenland, Norway,
shores of Massa-
chusetts
Lepidonotus caeloris Vicinity of San Diego, 71-75 SPSS
Calif.
Lepidonotus caeloris La Jolla, Calif. 243-280 5°=7°
Lepidonotus caeloris Santa Catalina Island, 143-245 5°-8°
Calif.
Lepidonotus caeloris Off Santa Barbara 29 9°-14°
Lepidonotus caeloris Island, Calif.
Lepidonotus caeloris San Nicolas Island, 32-33 9°-14°
Calif.
Lepidonotus caeloris San Nicolas Island, 229-291 5°-7°
Calif.
Lepidonotus caeloris San Nicolas Island 216-239 onli
Calif.
Lepidonotus caeloris Santa Cruz Island, 447-510 Deh

Calif.

* In table 5 an attempt has been made to enumerate all the species of Polynoidae known
on the Pacific coast in relation to the localities, depths and temperatures in which each species

is known to oceur.

a considerable difference has been allowed for seasonal variation.

y . The data regarding the temperature are not exact but in most cases
an approximate estimation of the possible temperature has been made by Dr. G@. McEwen and

7+* Temperatures printed in bold face represent actual observations.
tures were computed by Dr. G. F. McEwen and are entered to give a general idea of the
temperature at the corresponding depths.

The other tempera-

1918]

Name
Lepidonotus caeloris

Lepidonotus caeloris
Lepidonotus caeloris
Lepidonotus caeloris

Lepidonotus caeloris
Lepidonotus caeloris

Lepidonotus caeloris
Lepidonotus caeloris
Lepidonotus caeloris
Lepidonotus caeloris
Lepidonotus caeloris

Lepidonotus caeloris

Lepidonotus caeloris
Polynoé fragilis

Polynoé fragilis
Polynoé fragilis
Polynoé fragilis
Polynoé fragilis

Polynoé fragilis

Polynoé lordi
Poiynoé lordi

Polynoé lordi
Polynoé lordi

Polynoe lordi
Polynoé pulchra

Polynoé pulchra
Polynoé pulechra
Polynoé pulchra
Polynoé pulchra
Polynoeé pulchra

Polynoé pulchra
Polynoé pulchza

TABLE 5— (Continued)

Position
Santa Cruz Island,

Calif.

Santa Rosa Island,

Calif.

Monterey Bay, Calif.
Monterey Bay, Calif.
Monterey Bay, Calif.
At many points be-
tween Vancouver
and Kadiak Islands
Off the coast of Japan
Stephens Passage,

Alaska
Monterey Bay, Calif.
Off Cape Colnett,

Lower California
San Clemente Island,

Calif.

San Clemente Island,

Calif.

San Pedro, Calif.
Pleasant Beach, near

Seattle, Wash.
Puget Sound, Wash.
Salmon Bay, Wash.
Admiralty Inlet, Wash.
Fort Point, San

Francisco Bay
Sausalito Ferry,

San Francisco Bay
Yakutat, Alaska
Alki Point, Puget

Sound, Wash.
Anacortes, Wash.
Cape Mendocino,

Calif.

San Pedro, Calif.
Point Loma, San

Diego, Calif.

Santa Catalina Island,

Calif.

San Nicholas Island,

Calif.

Monterey Bay, (on

Luidia), Calif.
Monterey Bay, Calif.
San Pedro, Calif.

Off Coronado, Calif.
La Jolla, Calif.

Depth
in
fathoms

197-281.
38-40
285-357
368-495

26-28
18-313

50-57

1400

135-500

48

17-33

39

71-75

156-162

Qo
ao

56-62

40-46
40-150
8-10

40

Essenberg: Distribution of the Polynoidae

Tempera-
ture

B="
Syealays
sti

5°-10°
10°—-12°

13°
3°-4°

4°-10°

10°—12°

J) Sa

10°4

g°_g°
8°-9*
=)
3) Ue
8°-10°
Silo

12°-18°
10°-14°

185

Other localities

_ 186

Polynoe
Polynoe
Polynoe

Polynoé
Polynoé

Polynoe
Polynoe
Polynoé
Polynoeé
Polynoé
Polynoe
Polynoe
Polynoe
Polynoeé

Polynoé
Polynoe

Polynoe
Polynoe
Polynoé
Polynoé

Polynoé

Harmothoé imbrieata

Name
pulchra
pulchra
californica

ealifornica
ealifornica

ealifornica
ealifornica
ealifornica
ealifornica
ealifornica
ealifornica
ealifornica
ealifornica
ealiforniea

californica
remigata

filamentosa
aciculata
renotubulata
spicula

spicula

TABLE 5— (Continued)

Depth
ip
Position

San Diego Bay, Calif. I=
San Diego Bay, Calif.
Off San Nicholas
Island, Calif.
Monterey Bay, Calif. 10

Off San Diego Bay, 90
Calif.

Off San Diego Bay, 65
Calif.

Off San Diego Bay, 19-31
Calif.

Off San Diego Bay, 8-11
Calif.

Off San Diego Bay, 5-9
Calif.

Off Coronado Islands, 15-18
Calif.

Off San Pedro, Calif. 4-10

Off San Pedro, Calif. 35-36

Avalon, Santa Catalina
Island, Calif.

Santa Barbara, Pacific
Grove, Calif.

Humboldt Bay, Calif.

Santa Catalina Island, 334-600
Calif.

Santa Catalina Island, 334-600
Calif.

Vicinity of San Diego, 549-585
Calif.

Off Santa Catalina 2228
Island, Calif.

Otf Monterey Bay, 46-56
Calif.

San Nicolas Island 30-32

Yakutat, Muir Inlet, 35-36

Kakiak Islands, Al-
aska; Alki Point,
Puget Sound, Wash. ;
Trinidad; Humboldt
Bay, Shelter Cove,
Mendocino, Point
Arena, Dillon’s
Beach, Tomales Bay ;
Fort Point, San
Francisco Bay, Pa-
cific Grove, La Jol-
la, San Clemente
Island, San Pedro,
Calif. :

fathoms

40-48
291—298

University of Califorma Pu6lications in Zoology

Tempera-
ture

13°—25°

13°-25°

5°

Saas

Dealt

10°—16°

Sits

14°-19°

Ni

Malte
9°13"

UGS Nas

[ Vou. 18

Other localities

Round the shores of

British Isles; Si-
beria; Greenland;
Nova Zembla; To-
tomi Sea, 12-13
fathoms; Spitzber-
gen; Iceland; Sean-
dinavia; Adriatic
and Mediterranean
Seas; along all
European shores

1918]

Essenberg: Distribution of the Polynoidae

Name

Harmothoé
Harmothoé
Harmothoé
Harmothoé
Harmothoé

Harmothoé
Harmothoé
Harmothoé
Harmothoé
Harmothoé
Harmothoé

Harmothoé

Harmothoé
Harmothoé
Harmothoeé

Harmothoé
Harmothoé

Harmothoé
Harmothoé
Harmothoé
Harmothoé
Harmothoé
Harmothoé
Harmothoé

Harmothoé

Harmothoé

Harmothoé yokohamiensis

imbricata
imbricata
tuta

erassicirrata
iphionelloides

seriptoria

tenebricosa
tenebricosa
tenebricosa
tenebricosa
multisetosa

multisetosa

multisetosa
multisetosa
multisetosa

multisetosa
multisetosa

multisetosa
multisetosa
lamellifera
lamellifera
lamellifera
lamellifera
lamellifera

lamellifera

lamellifera

Harmothoé yokohamiensis
Harmothoé yokohamiensis
Harmothoé yokohamiensis
Harmothoé yokohamiensis
Harmothoé triannulata

Harmothoé triannulata

Harmothoé fragilis
Harmothoé fragilis

TABLE 5— (Continued)

Position

San Diego, Calif.

San Diego, Calif.

Puget Sound, Wash

Monterey Bay, Calif.

Pleasant Beach,
Wash.

Monterey Bay, Calif.

San Diego Bay, Calif.

Monterey Bay, Calif.

Monterey Bay, Calif.

San Diego Bay, Calif.

San Clemente Island,
Calif.

Santa Cruz Island,
Calif.

Monterey Bay, Calif.

Monterey Bay, Calif.

Cape Colnett, Lower
California

Gulf of Georgia,
Alaska

Boca de Quadra,
Alaska

Vancouver Island

Vancouver Island

Near San Diego, Calif.
Near San Diego, Calif.
Near San Diego, Calif.
Near San Diego, Calif.

San Clemente Island,
Calif.

San Nicolas Island,
Calif.

Santa Cruz Island,
Calif.

Santa Catalina, Calif.

Santa Cruz Island,
Calif.

Santa Cruz Island,
Calif.

Monterey Bay, Calif.

Monterey Bay, Calif.

San Nicolas Island,
Calif.

Santa Rosa Island,
Calif.

San Diego Bay, Calif.

San Diego Bay, Calif.

Depth
in
fathoms

Sill!
19-31

100

49-50
500-507
540-800
545-800
500-507
654-704

447-510
49-51
759-766
1400
18—23
48-57
IOLA)
31-90
67-116
71-75
241-369
639-671
654-704
1100
764-891
152-162
447-510
197-281

368-495

1041-1062

238

38-41

423-488
500-507

Tempera-
ture

12°-18°
LOS—162

Sie
Soe
Oa)
2°-4°
4°1
Soe
(0s
Qin
10°.7
Wath
9°05
11°1
5 ised bl La
5°-6°
4°
4°1
BO
3°—4°
fr
ion
Z-=o
304°
2°-3°
3°—4°

8°-13°

32D
3°-5°

187

Other localities

Sitka, Korea

Yokohama, Japan,
5-50 fathoms

188

University of California Publications in Zoology [Vou.18

Name

Harmothoé
Harmothoeé
Harmothoé
Harmothoe
Harmothoe
Harmothoe
Harmothoeé
Harmothoé
Harmothoeé
Harmothoe
Harmothoé
Harmothoeé
Harmothoe
Harmothoeé
Harmothoé
Harmothoé
Harmothoé
Harmothoé

Harmothoé

Harmothoé
Harmothoé

Harmothoé

Harmothoé

Harmothoé

Harmothoé
Harmothoé

Harmothoé
Halosydna

Halosydna

fragilis
fragilis
fragilis
fragilis
fragilis
fragilis
fragilis
foreipata
forcipata
foreipata
complanata
ecomplanata
pacifica
hirsuta
hirsuta
hirsuta
hirsuta
hirsuta

hirsuta

hirsuta
truncata

truneata

truneata

truneata

truncata
bonitensis

johnsoni
insignis

insignis

TABLE 5—(Continued )

Position

San Clemente Island,
Calif.

Santa Catalina Island,
Calif.

Santa Barbara Island,
Calif.

San Nicolas Island,
Calif.

San Nicolas Island,
Calif.

San Miguel Island,
Calif.

Santa Barbara Island,
Calif.

San Clemente Isiand,
Calif.

Santa Cruz Island,
Calif.

Santa Cruz Island,
Calif.

Puget Sound, Wash.

Coronado, Calif.

Locality unknown

San Pedro, Calif.

Santa Barbara, Calif.

La Jolla and San
Diego, Calif.

Port Townsend, Wash.

Pacific Grove, Calif.

Dundas Bay, Icey
Strait, Alaska

Pillar Point, Calif.

Halibut bank, Gulf of
Georgia, Alaska

Halibut bank, Gulf of
Georgia, Alaska

Queen Charlotte Sound,
off Vancouver Island,
Buc:

Admiralty Inlet, Port
Townsend, Wash.

Behm Canal, Alaska

Point Bonita, San

Francisco Bay, Calif.

La Jolla, Calif.

Kadiak Island,
Alaska

Alki Point, Puget
Sound, Wash.

Depth
in
fathoms

542-600
152-162
238-310
291-298
216-339
264-271
197—281
448468
447-510

506-580

3-4

Tempera-
ture

4°4

Other localities

Gre

4°-5° } f ae | { se

Eno-Sima, Japan

14°—18°
14°-18°
14°—20°
10°4
7°05

6°78
5°=10°

10°28

6°56
12°6

13°—22°
4°95

5°

1918 |

Name
Halosydna insignis
Halosydna insignis

Halosydna insignis

Halosydna insignis

Halosydna insignis
Halosydna insignis

Halosydna
Halosydna

insignis
insignis
Halosydna insignis
Halosydna

Halosydna

insignis
insignis

Halosydna
Halosydna
Halosydna
Halosydna

insignis
insignis
insignis
insignis

Halosydna interrupta

Halosydna
Halosydna

interrupta
interrupta
Halosydna lagunae
Halosydna
Halosydna sueciniseta
Halosydna macrocephala
Eunoé barbata

Eunoé barbata

Kunoé barbata

Eunoé barbata

Eunoé caeca

lagunae

Eunoé depressa
Antinoé macrolepida
Antinoé anoculata

Antinoé anoculata

Nemidia microlepida
Lepidasthenia gigas
Lepidasthenia gigas

TABLE 5—(Continued)

Position

Admiralty Inlet,
Wash.

Cape Mendocino,
Calif.

Point Arena,

Dillon’s Bay,

Tomales Bay, Calif.

Duxberry Reef,
Bolinas, Calif.

San Francisco Bay,
Calif.

Point San Pedro,
Calif.

Pillar Point, Calif.

Monterey Bay, Calif.

Monterey Bay, Calif.

Pacific Grove, Calif.

Avalon, Santa Catalina
Island, Calif.

La Jolla, Calif.

San Pedro, Calif.

Point Firmin, Calif.

‘San- Nicolas Island,

Calif.
Off La Jolla, Calif.

Point Firmin, Calif.
Point Loma, near
San Diego, Calif.
Near San Diego,
Calif.
Laguna, Calif.
Laguna, Calif.
Off San Diego, Calif.
Blount’s Reef, Calif.
Puget Sound, Wash.
Monterey Bay, Calif.
Admiralty Inlet, Wash.
Monterey Bay, Calif.
(on holothurians)
Dundas Bay, Alaska
Monterey Bay, Calif.
Coronado Island,
Calif.
Monterey Bay, Calif.
Monterey Bay, Calif.
San Pedro, Calif.
Zuninga, Calif.

Depth
in
fathoms

24-25

10
15-26

861-1062

8-10
75-108
618-667

750-766
130-149
50

Essenberg: Distribution of the Polynoidae

Tempera-
ture

10°17

IOUS

Werle

Deal

8°89

13°=21°

10°—22°

We Aichi”
9°—14°
5°-8°

8°—13°

189

Other localities

Sagami Bay, Japan,
153 fathoms

Eno-Sima, Japan
480 meters or 250
fathoms

190 University of California Publications in Zoology [Vou. 18

TABLE 5—(Concluded)

Depth
in Tempera- Other
Name Position fathoms ture localities
Lepidasthenia gigas Point Loma, San 50 QP Ss
Diego, Calif.
Lepidasthenia gigas Off Point Firmin, 60-140 O.—135
Calif.
Gattyana senta San Diego Bay, Calif. 91-97 4°-6° McCormick Bay
Gattyana senta San Diego Bay, Calif. 127-3800 2°-3° Gulf of Georgia,
18-23 fathoms
Gattyana senta San Nicolas Island, 32-33 10°—-14° 31-90; 157-230
Calif. fathoms
Gattyana senta Monterey Bay, Calif. 48-111 10°-12° Behm Canal, Alaska,
41-134 fathoms
Gattyana senta Monterey Bay, Calif. 30 ae—7°
Gattyana amundseni Stephens Passage, 131-188 4°9
Alaska
Gattyana amundseni Alitak Bay, Kodiak 35-36 6°89
Island, Alaska
Gattyana amundseni McCormick Bay, 16 Seon
Greenland
Gattyana ciliata Uyak Bay, Kodiak 74-80 5°6
Island, Alaska
Gattyana ciliata McCormick Bay, St. Andrews Bay,
Greenland Atlantic, 580-630
fathoms
Gattyana cirrosa Afognak Bay, Alaska 12-17 8°-11° Norway, Finmark,
Gulf of St. Law-
rence
Gattyana cirrosa Barden Bay, Greenland 10-40 10°=1.2° aAkoY *
Melaenis loveni Iey Cape, Alaska
Lagisea rarispina Gulf of Georgia, 18-23 10°1
Alaska
Lagisea rarispina Gulf of Georgia, 157-230 8°7
Alaska
Lagisea rarispina Admiralty Inlet, Port 16-20 10°1
Townsend, Wash.
Lagisca rarispina Boca de Quadra, 149-181 6°9
Alaska
Lagisea rarispina Yes Bay, Behm Canal 130-193 ihe
Lagisea rarispina Stephens Passage, 131-182 4°89
Alaska abundant
Lagisea rarispina Lynn Canal 300-313 5°11
abundant
Lagisca rarispina Dundas Bay, Icy 614-9 i GEU
Strait, Alaska :
Lagisea rarispina Uyak Bay, Kodiak 74-80 6°78
Island, Alaska
Hololepida magna Gulf of Georgia on 157-230 722
halibut bank
Hololepida magna Kasan Bay, Prince of 95-114 4°—6°

Wales Island, Alaska

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4

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UNiV. CALIF. PUBL. ZOOL. VOL. I8

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1918 | Essenberg: Distribution of the Polynoidae 191

D. FACTORS CONTROLLING DISTRIBUTION

On the basis of the above examples the Polynoidae of this coast
may be grouped according to their horizontal distribution into sub-
boreal, temperate, subtropical, tropical and cosmopolitan species; and
according to their vertical distribution they fall into littoral, sub-
littoral, and deep water groups. These facts suggest that there must
_be some reason for such varied distribution, or else the distribution
would not occur in such a constant and definite manner. Assuming
that all actions are in response to stimuli, the phenomenon of distri-
bution may be best understood by considering the factors or stimuli
which play a role in distribution. Many of these factors are un-
doubtedly so complex that they can be studied only by complicated
methods of chemical and physical analyses. The most obvious factors,
however, may be enumerated as follows: (1) temperature, (2) ecur-
rents, (3) winds, (4) chemical composition of the water, (5) food
habits and mode of life of the Polynoidae.

I. TEMPERATURE IN RELATION TO DEPTH AND LATITUDE

Before we speak of the influence of the temperature on the oceanic
fauna and flora, and of the réle it plays in distribution, it is essential
to have a clear conception of the relative temperatures of the various
depths and latitudes. As far as it is known from the hydrographic
records of the various investigations of the oceans, the bottom tem-
peratures of the depths of the Pacific Ocean are remarkably uniform,
ranging from 1°26 to 1°99C (Schott and Schu, 1910; MeEwen, 1915).
There is a very slight variation in temperature in abyssal waters
below 2,000 fathoms. The bottom waters are the coldest near the
California coast. The temperature becomes gradually warmer with
the increasing distance from the shore, but the variation of the tem-
perature amounts only to a difference of 0°45 Fahrenheit between the
longitudes 120° and 160° (Clark, 1916) or from the coast of Califor-
nia toward the mid-Pacific. This difference in temperature is so
insignificant that it is almost negligible.

This, however, is not true of the surface temperature, which is far
from being uniform; in fact, considerable fluctuations in temperature
due to various physical causes are found in comparatively small areas.
Considering the surface temperature of the entire Pacific coast in
general, one finds that it follows certain laws varying according to

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198 Unversity of California Publications in Zoology [Vou. 18

latitude and, to some extent, according to longitude. The highest
temperature of the surface waters of the ocean, as one may naturally
expect, 1s in the lowest latitudes on both sides of the equator, where the
intensity of the solar radiation reaches its maximum. With an
increase in distance from the equator toward the poles there is a grad-
ual decrease in temperature. The difference in temperature is here
about 28° to 29°C, ranging from 28°5C near the equator to 1°4C at
latitude 60° (see table 6) or to 0° in the North Polar Basin at about
80° latitude. Again, a difference in surface temperature prevails
between the surface waters of the coastal region and those of the mid-
Pacific, and as a general rule the temperature of the surface water
rises with the increase in distance from the Californian coast toward
the mid-Pacific. But in the mid-Pacific, as well as near the coast, the
temperature gradually decreases with the increase in distance from
the equator toward the poles. The temperature near the shores, how-
ever, 18 more subject to fluctuations due to various causes. Thorade
(1912) has shown in detail the variations in temperature off the coast
of California with isotherms for surface temperatures for each month

ce

of the year. Certain ‘‘cold islands’’ surrounded by warmer waters,
off Seattle and San Francisco, disappear entirely during some months
but are very prominent in others, the appearance and disappearance
of these ‘‘cold islands’’ being caused by the seasonal changes in winds
with their influence upon the waters. The shifting of the isothermal
lines near the shores is also conspicuously noticeable in the varying
seasons. Upwelling of the cold bottom waters is the cause of cold
belts along the coast of California (Holway, 1905). An instance of
narrow cold water belt is found in the waters along Cape Mendocino.
Some limited areas of shallow water near the coast have higher tem-
perature than the surrounding deeper waters. All these complexities
help to diversify the thermal conditions of the surface waters, but
on the whole the temperature decreases with the increase of distance
' from the equator to the poles (table 6).

In the Arctic Ocean the surface temperature is nearly like the
bottom temperature, varying from 1°80C in April to O0°80C in
August. The temperature in the different depths in that region varies
from 0°30 to 0°80C (Nansen, 1902) being also uniform in that
region. This, however, is not true in the lower latitudes, where the
temperature varies with the various depths, decreasing gradually
with the increase in depth until in the greatest depth a minimum tem-
perature is reached which is nearly identical with that of the Arctic
waters.

1918 | Essenberg: Distribution of the Polynoidae 199

Fig. A. Distribution of surface temperatures off the Pacific coast of North
America in January and May. After Thorade (1909).

200 University of California Publications in Zoology [Vou. 18

Schott and Schu (1910) have tabulated the temperatures of the
various depths and latitudes from depths of 0 meters to 4,000 meters
and from 60°N latitude to 50°S latitude. Their table and the map of
the Pacific coast give a very good idea of the distribution of the tem-
perature in the different depths and latitudes (see tables 6 and 7).
Comparing some of the data in this table we find that the tempera-
tures of the various depths near the equator correspond to the tem-
peratures of the various latitudes. The temperature at a depth of
3,000 meters near the equator corresponds to the surface temperature
of 60°N latitude. The temperature of the water at a depth of 1,500
meters is identical with the surface temperature at 55° latitude. The
temperature at 1,000 meters depth at 0° latitude is equal to the sur-
face temperature of 50° latitude. The temperature in the depth of
400 meters is equal to the surface temperature at 40° latitude. The
temperature at 200 meters at 0° latitude is equal to the surface tem-
perature of 30° latitude, and the temperature in the depth of 100
meters at 0° latitude is identical with the surface temperature of
20° latitude.

Il. TEMPERATURE AS A Factor CONTROLLING DISTRIBUTION

The above facts show that the vertical distribution of the tempera-
ture from the surface to the bottom in the lower latitudes is com-
parable to the horizontal distribution from the equator to the poles.
In some places along the coast the changes in temperature are so
abrupt that definite geographical points serve as division lines of
different isothermal areas. If the distribution of certain species of
animals and plants coincide with the distribution of the temperature
zones, aS has been observed to be the ease, it is obvious that the tem-
perature may be regarded as one of the main factors controlling the
distribution of Polynoidae.

It is a well known fact that a strong heat in summer may kill all
_ the shallow water plants within a few days by raising the temperature
beyond the maximum which those plants ean stand. Many organisms
of phytoplankton occur in shallow water in winter, but in deep water
during summer. The phytoplankton in the Gulf of Naples was not
found in surface layers but in a depth of 200 fathoms where the water
is considerably cooler, while in the oceans of higher latitude, as in the
North Sea, where the surface temperature is lower, the diatoms and
Peridiniae are found at the surface. In these regions, again, the depth

1918 | Essenberg: Distribution of the Polynoidae 201

‘inn
eattle 2h ley

n
fo)

Ze:

IN
IN

=

ct

AS
Pes
bie _—
ais

Fig. B. Distribution of surface temperatures off the Pacific coast of North
America in July and August. After Thorade (1909).

202 University of California Publications in Zoology (Vou. 18
y gy

of the habitat of the plankton varies with the seasonal changes. At the
beginning of the summer the plankton generally is abundant at a
depth of 20 meters. With the increasing surface temperature, how-
ever, it gradually sinks to greater depths and in late summer it is
found at a depth of 60 to 80 meters (Steuer, 1911).

Observations on Sagitta bipunctata have revealed the fact that this
species increases in abundance as the temperature increases from
9° to 14° and decreases as the temperature increases from 16° to 21°
(Michael, 1916). This is a clear proof that the maximum tempera-
ture for that species lies between 14° and 16°; hence the species
undergoes an oscillation downward or upward with the increase or
decrease of surface temperature.

It has also been observed that some animals, such as medusae,
crustaceans and pteropods, come to the surface during the night, and
sink to a greater depth during the daytime. A sudden change in
temperature may kill the larvae of aquatic animals. Murray and
Hjort (1912) have observed that if the eggs of Cucwmaria are shed
in summer when the surface temperature of the Arctic waters is
high, they are killed without hatching a single larva. Adult animals,
as a rule, can stand more fluctuation of temperature, but there is a
maximum and a minimum temperature above or below which the
animals cannot live. The power of adaptation differs in different
animals and consequently the maximum and minimum temperature
eannot be the same for all animals. Hence the species will become
adapted to that environment which is best fitted for its existence;
while animals unable to adapt themselves perish. In whatever way
temperature affects animals, it is evident that it plays an important
role in their distribution by serving as a barrier.

One of the best illustrations of the effect of temperature is Wyville
Thomson’s Ridge. This ridge stretches from Iceland to Shetland,
separating the Atlantic Ocean from the Norwegian Sea. The tem-
perature in the upper strata of water, extending from 400 to 500
meters depth, is the same on both sides of the ridge, and the fauna
of the upper strata is alike in both regions. But at a depth of 1,000
meters the temperature on the Norwegian side is below 0°, while on
the Atlantic Ocean side it is 6° to 7°. The deep sea faunas on the
opposite sides of the ridge differ greatly. Of 216 species taken from
the depths of the warmer region, and the 217 species from the: colder
region, Murray (1898) found that only 48 species were common to
both sides. Other oceanic areas where the temperature changes less

1918 | Essenberg: Distribution of the Polynoidae 203

abruptly show the same corresponding gradual changes in faunal
distribution.

Izuka (1912) shows that the Kyushiu Island is an important
boundary line of distribution. Numerous northern species cease to
exist south of Satsuma, and the southern species do not extend north
beyond that point. On the Pacific side, the island Kinkwasan forms
the boundary line of distribution of annelids. The cold water species
rarely extend south of Kinkwasan Island, and the warm water species
do not occur north of that island. Here again the chief factor, if not
the only factor, controlling distribution is temperature. This differ-
ence in temperature is caused by the cold and warm currents sweep-
ing past the Japanese Islands. The islands there form a natural
division line between the warm and cold oceanic areas. Hence it is
natural to find the northern species occupying the cold area on one
side of the island; while on the other side of the island, in the warmer
area, the warm water species only occur.

An evidence of the influence of temperature on distribution is the
fact that aretie littoral species of polynoids, with a few exceptions,
appear as deep water forms in warm oceans. On this coast a few
species of Polynoidae are known which inhabit the littoral areas in
the boreal zones, while nearer the equator, in warmer waters, they
inhabit greater depths. As examples may be cited the following
species: Gattyana amundsent, Gattyana cirrosa, Harmothoé multi-
setosa and Lepidonotus caelorus.

Gattyana amundsent has been found off Greenland, at about 77°
latitude, as a littoral form at a depth of 16 fathoms, while in lower
latitudes along the coasts of Alaska, it occurs in deeper waters between
50 and 100 fathoms depth (table 5). Comparing the temperatures of
the corresponding latitudes we find that the temperature in waters
of Greenland is about 0°, while near the Alaskan coasts, about 58°
latitude, it is about 1°4 to 2°. . In a depth of 100 meters, however,
about 50 fathoms, the temperature at the latter latitude is 0°4 (see
tables 6 and 7), which is about identical with the temperature of the
shallow waters off Greenland.

Gattyana cirrosa oceurs in the Arctic oceans off Greenland and
Alaska, about 60° to 70° latitude, in depths of 10-12 fathoms, while
the same species occurs off the shores of Great Britain, about 55°N
latitude, at a depth of 600 fathoms. The surface temperature at the
coresponding latitudes differs considerably but the temperature of
600 fathoms depth off the shores of Great Britain is nearly identical

204 University of California Publications in Zoology [Vou. 18

with the surface temperature off Greenland and that of the coasts of
Alaska.

Harmothoé multisetosa is found in the lower boreal zone, along.
the shores of Alaska, in depths of from 18 to 23 fathoms. In the
temperate and subtropical zones it occurs in depths varying from 50
to 750 fathoms. It is more abundant beyond the 500 fathom line,
only one ease at a depth of 50 fathoms having been reported from
Monterey Bay where the species occurred. Off Cape Colnett, in Lower
California, however, the species occurs in 1,400 fathoms depth. Again,
comparing the temperatures of the corresponding latitudes and the
depths (tables 6 and 7) given in connection with the distribution, we
find that the species, although occupying widely separated areas and
different depths, lives in identical temperatures, and evidently for
that very reason is found in deep waters in the subtropical regions,
where the temperature is the same as that of the shallow waters of
subboreal regions. . With a farther advance toward the tropical regions,
its habitat extends to greater depths, and this is true of the tempera-
ture (table 6). In order to find the temperature identical with that
of the Arctic waters, one must seek it in deeper and deeper water as
he approaches the equator.

Another species, Lepidonotus caclorus, occurs in abundanee and in
various depths on this coast mostly between 70 and 500 fathoms. Off
Cape Colnett, Lower California, the species occurs at a depth of 1,400
fathoms. The temperatures of the various depths occupied by this
species, however (table 6), are identical. These facts seem to prove
that species, although they may occupy widely separated geographical
areas, do live in identical temperatures. [Speaking of identical tem-
peratures, one has to keep in mind that the temperature of an entire
life zone, and not of one particular point is considered ; consequently
an allowance for variation in temperature of about five degrees or
more should be made.| Similar observations were made by Ehlers
(1875) who found that Arctic species of annelids outside of the Arctic
realm always inhabited considerable depths, and were never found at
the depths frequented by the same species in colder regions. This was
shown remarkably well in some parts of the Norwegian Sea, where
near shore the temperature is constant, ranging from 6° to 7°. Ap-
proaching the deeper basin of 600 meters the temperature is about 0°,
or identical with the temperature of Arctic waters. A corresponding
difference in distribution of annelids was also found there. In the
warmer areas, nearer shore, were found the warm water annelids which

1918 | Essenberg: Distribution of the Polynoidae 205

had migrated from southern latitudes, while in the greater depths
exclusively arctic species predominated.

The observations of investigators in other fields of animal life
strongly support the view that to a great extent temperature deter-
mines the distribution of oceanic fauna. The studies on Dinoflag-
ellata prove that certain species of Gonyaulax (Kofoid, 1907, 1911)
may be designated as distinctly warm water forms oceurring in the
warm waters of the tropical and subtropical zones on this coast as well
as in other oceans, while the species occurring in the subboreal regions
on this coast are also reported from other parts of the world from
the cold waters. The ascidians of this coast (Ritter, 1913) are dis-
tinguishable as boreal, subboreal, and temperate species, each group
being limited strictly to its temperature zones.

Furthermore, we find that the same temperature relations prevail
in the distribution of terrestrial fauna and flora. Contrasting the
valleys and mountains, where the difference in temperature 1s con-
siderable, we find that many species of animals are restricted to valleys
in higher latitudes which in lower latitudes in tropical areas, inhabit
higher altitudes or the alpine zones; while the lowland species of a
subtropical or tropical zone do not ascend to the higher altitudes of
that latitude. Oregon lowland forms of insects extend southward
into California where they seek a higher altitude. Some species, like
Tragosoma harrisii, occur from Sitka to California. In the cooler
regions in the higher latitudes, they are found in lowlands. They rise
as they approach a more southern region until in the subtropical Cali-
fornian areas they inhabit the zones above 10,000 feet altitude
(Cockerell, 1893). Furthermore, some Coleoptera which occupy the
lowlands in temperate zones occur as alpine species in the Andes in
Eeuador and are never found in tropical lowlands. Some Coleoptera
which oceur as alpine and subalpine species in the tropical and sub-
tropical areas of North America are found in Canada, Lapland and
other northern countries as lowland species.

Comparing the high-alpirie, mid-alpine and subalpine species of
insects of tropical zones we find again that each zone has its distinct
species which do not occur in the adjacent zones. The level at which
certain species may be found varies with the season, the line rising
up the hill during summer and receding towards the valley in winter.
The valleys and the mountains on the dry land, as far as the tem-
perature is concerned, are comparable to the shallow and deep waters
in the oceans. The effect on distribution is comparable in the two
cases.

206 University of California Publications in Zoology (Vou. 18

These observations lead to the conclusion that the distribution of
Polynoidae, which occurs in a definite manner, is not a mere accident,
but that it is governed by some underlying principles or factors. One
of the chief controlling factors undoubtedly is temperature.

III. ROLE oF CuRRENTS IN DISTRIBUTION

The locomotion of Polynoidae is by means of swimming and crawl-
ing, the latter method being the more common. If a polynoid is brought
to the surface of the water, it swims with undulating motions, soon
returning to the bottom. The writer has never seen an adult polynoid
rise to the surface under ordinary circumstances and swim, aS many
other polychaetous worms do. Keeping various annelids in aquarium,
the writer has observed that some of them, e.g., Phyllodocidae, Nephthy-
didae, if disturbed rise to the surface and swim about vigorously, and
very often when the aquarium overflows the worms are found outside
of the aquarium. The Polynoidae, however, do not leave the aquarium
even when the latter overflows. This shows that they habitually lve
on the bottom, crawling about slowly, searching for their food in the
mud and eapturing other smaller animals or attacking one another.

Since the Polynoidae are bottom dwellers and are not known to be
very powerful swimmers, how then shall we account for their wide
distribution? With their limited powers of locomotion they could
not possibly traverse distances of thousands of miles, yet the ecosmopoli-
tan species occur in all oceans, as I have stated, from the Aretie Ocean
to and south of the equator (table 5). Some Pacific coast species as
Harmothoé hirsuta inhabit the northern subtropical zone along the
shores of southern California, but one example of this species, how-
ever, has been found on the coast of Chile. Harmothoé forcipata also
is known to occur abundantly on the coast of southern California
(Moore, 1910). One specimen has been found near Eno-Sima, Japan
(Ehlers, 1875), and another specimen has been found on the north
coast of Korea at a depth of 1400-1600 meters (Marenzeller, 1902).
Harmothoé tuta has been reported from Sitka (Grube, 1855) and
from Puget Sound (Johnson, 1901). Harmothoé yokohamiensis has its
habitat along the coast of California (Moore, 1910), but one example
has been reported from Yokohama, Japan (MeIntosh, 1885). A num-
ber of examples of Gattyana senta have been taken on the southern
coast of California, but the same species has also been reported from
MeCormick Bay, Greenland (Moore, 1902). Numerous eases of this

1918 | Essenberg: Distribution of the Polynoidae 207

kind are known in which Polynoidae are found occupying areas that
are separated, sometimes by thousands of miles. Considering those
species with relatively few individuals and found in widely separated
areas, we come to the conelusion that the creatures would never have
arrived there by their natural means of locomotion, but that there must
be some natural factor or agent facilitating their distribution.

One of the best means of dispersal is undoubtedly the oceanic cur-
rents. These may influence the distribution indirectly or directly.
First, by influencing or changing the temperature of the water. See-
ondly, by carrying terrigenous debris and small oceanic animals to
some places, thus preparing better feeding grounds for the Polynoidae.
Or the powerful currents may remove the debris from other places
leaving the rocks bare and unsheltered, thus changing food conditions.
Acting directly the currents may carry adult worms along the bottom
of the ocean or in weeds along the surface. The latter mode of trans-
portation is known to be true of Nereis. Nereis dumcrilii was collected
in the middle Atlantic Ocean (Ramsay, 1913) where it had suposedly
drifted from the neighborhood of the Gulf of Mexico with the south-
west drift. Nereis mirabilis has been recorded from the coasts of
Brazil, Florida, Porto Rico, Bermuda, the Red Sea and the Persian
Gulf. Since this species lives and breeds in the algae it is supposed
to have been carried out with the floating weeds.

But the usual way of transportation probably is that of carrying
the eggs and pelagic larvae of the worms. If the pelagic larvae hap-
pen to be caught in a current, they may drift very rapidly to great
distances. This may account wholly for the wide distribution of some
of the Polynoidae.

One would naturally inquire why there are not more annelids
seattered in the ocean and why in so many eases only a few specimens
of some particular species are found in restricted areas far away from
their natural habitat. The reason, apart from imperfections of obser-
vations, that only a few individuals of a species are found far away
from their original home may be due to their becoming there the prey
of natural enemies. The greatest impediment, however, would be the
sudden changes of temperature which would destroy the larvae. For
instance, the larvae of arctic Polynoidae if carried to tropical zones,
would probably be killed by the high temperature of the surface waters.
Their survival would depend greatly upon the season in which the
larvae were carried, and upon the character of the bottom where they
happened to drop in changing from the trochophore to the adult stage.

208 University. of California Publications in Zoology |Vou. 18

On the other hand, assuming that the arctic larvae were carried to
the lower latitudes in a favorable season, 1.e., during the coldest months,
the larvae, although they would have more chance to survive on their
journey, would nevertheless sooner or later be killed by the temperature
if they happened to be driven to warm shallow waters in the tropical
zones. Those that were carried to deep waters would find a tempera-
ture identical with that of their natural habitat, and would survive
and adapt themselves to the new surroundings. Considering their
numerous enemies and unfavorable conditions one realizes that there
is very little chance for the larvae to survive and probably for that
reason we find very few individuals, and those in limited areas far
away from their original habitat. Such supposition would explain
why the aretie species of Polynoidae, when found on the coasts of Cali-
fornia, are so largely deep water inhabitants. As exceptions to this
are the cosmopolitan species which are found on these coasts in shallow
waters. But it may be that in this species the plasticity and the power
of adaptation are more highly developed, so that they would be more
fit to survive the vicissitudes of such transportation. Probably for
that very reason they are so widely distributed.

The most powerful oceanic current on this coast aiding in the
distribution of the oceanic fauna is the extension of the Kuro Siwo,
or Japan Current, flowing along the Pacific coast of North America,
striking the American coast at Sitka, Alaska. At this point it broadens
out, drifting slowly toward the equator and curving away from the
coast. The Japan Current is joined on the west side by the southerly
drifting surface waters which increase in volume and breadth until at
latitude 25° the current extends more than 1,000 miles off shore
(McEwen, 1915). This current undoubtedly serves as a powerful
agent of transportation or distribution of species. Probably it is due
to the action of this current that species from the coasts of Japan and
Alaska have representatives along the coast of California and near
the equator:

IV. THE WInpDs

In addition to oceanic currents, the winds may be regarded as
agents of distribution. The prevailing winds act upon the water,
causing cool upwellings of the bottom layers. This has been observed
to be the case along most of the Pacific coast of North America. This
upwelling water is driven in an easterly direction or toward the shore,
thus causing in some parts an inshore cold belt. With the moving body

1918 | Essenberg: Distribution of the Palynoidae 209

of water oceanic life may be carried away. This action is especially
noticeable after severe storms when deep water animals are found
washed ashore and when marine algae whose habitat is far off the
shores are also abundant on the beach. The same phenomenon is
known to occur on other coasts. After a severe storm the beach of
St. Andrews, Scotland, is known to be strewn with multitudes of
Aphrodita aculeata. These aphrodites are driven by the currents from
the offshore grounds, where they normally live in deep waters.

Many times after the retiring tides, the beach for a distance of a
mile or more has been covered with aphrodites and other deep water
species (MeIntosh, 1900). Gattyana cirrosa, which normally occupies
a depth of 600 fathoms in that region, has been found on the beach
after storms. Similar observations on the effect of storms have been
made on the coasts of Scandinavia. Since deep water species are
driven to the shores it is also probable that severe storms or even the
prevailing winds with their constant action on the waters may drive
animals from the shores into the depths.

V. CHEMICAL COMPOSITION OF WATER

As another factor controlling distribution may be mentioned the
chemical composition of the water. The differences in salinity may
influence the distribution of Polynoidae to some extent. Some species
of Polynoidae ean live in brackish waters as well as in salt. Some
species have even been found in river estuaries. Others, again, are
restricted to salt waters only. It is found that species most widely
distributed live under more varied conditions, while very restricted
species usually occur in similar environment even when they are found
widely separated. Evidently some species have acquired a greater
plasticity, while others may be more sensitive to changes in tempera-
ture and to chemieal effects, and would either perish or undergo con-
siderable changes. These chemical differences may also explain the
greater number of genera and species in the great depths, if their
environment were altered. Most probably littoral polynoids, migrat-
ing or driven to the depths of the ocean, are in a more or less patho-
logical condition in the abnormal environment, and undergo such
radical changes that they soon lose their identity with the ancestral
shore species. That animals in great depths undergo pathological
changes has been revealed by the studies on erimoids (Clark, 1915).
These animals reach their minimum specialization between 550 and

210 University of California Publications in Zoology [Vou. 18

750 fathoms, a depth which is the zone of an optimum temperature for
the group. Below 750 fathoms they undergo semipathological changes,
forming new genera and species. Murray (1898) suggests that the
ancestors of the fauna of great depths have migrated from many shal-
low water areas, hence the great diversity of genera. This would
hardly be necessary. If by sudden change in temperature different
kinds of beetles can be produced (Tower, 1906), and if changes in
temperature or treatment with potassium cyanide or magnesium sul-
phate can produce abnormal fish (Loeb, 1915; Stockard, 1909), it
seems entirely possible that chemical and physical agents in the depths
of the oceans may affect the deep water fauna in such a way as to
modify their external appearance to so great an extent that in time
the new generations are quite unlike their shallow water ancestors and
become new species. The great number of genera and species of deep
water Polynoidae may have been produced by the action of the chemical
and physical influences upon migrants from the littoral zone.

A further proof that similar chemical and physical conditions may
produce similar results affecting organisms equally is the fact that
identical species of aquatic animals are found in corresponding life
zones on both sides of the equator. Murray (1898) enumerates 150
identical species of Metazoa, and about 100 closely allied species, oceur-
ring in the extra-tropical regions of the northern and southern hemi-
spheres, which are wholly unknown from the intervening tropical belt.
This phenomenon suggests that similar chemical and physical condi-
tions have a tendency to produce similar results. Furthermore, it is
a generally known phenomenon that chitinous and calcareous animals
are abundant in the tropics, while animals secreting little or no lime
salts or chitin are more abundant in polar regions and in great depths.
The deep water Polynoidae of the Pacific Ocean have soft, thin scales
and cuticle. This condition may have been produced by chemico-
physical influences which arise in the colder waters in the depths.

VI. Foop Hapits AND Mops or Life

Polynoidae are voracious feeders, devouring any animal they can
capture. Their chitinous jaws are strongly developed and well adapted
for their purpose. In captivity they attack one another, severing seg-
ments and scales from the bodies of their companions; hence it is
difficult to keep alive a number of Polynoidae in the same aquarium,
for they inflict such serious harm to one another that they soon die.

—

1918 | Essenberg: Distribution of the Polynoidae 204

Smaller and weaker polynoids are usually devoured by their stronger
companions. They also feed on other annelids, small crustaceans,
mollusks, sponges, and other small animals, as well as diatoms which
are often swallowed with the debris. Some species living as com-
mensals become ectoparasites, feeding on their messmates.

In connection with their food habits it is interesting to observe the
modes of self defense or protection among the different species of
Polynoidae, as well as among other annelids. The Polynoidae naturally
hide beneath pebbles, empty mollusk shells or weeds in the aquarium.
Halosydna californica when disturbed or attacked by individuals of its
own kind moves away quickly but without any wriggling motions,
very often leaving behind the attacked posterior segments or elytra.
Some other Polynoidae act in the same manner. Harmothoé, on the
other hand, when disturbed moves very swiftly with a vibrating,
wriggling motion at first and then coils up, turning its ventral surface
inside of the ring and spreading out its spiny, rough seales and its
numerous serrated setae in such a manner as to protect the body.
Harmothoé imbricata and Harmothoé hirsuta have been observed to
use this mode of self defense. It seems as if the creatures knew
instinetively the value of their protective organs and how to use them
to the best advantage.

Other annelids that lack defensive organs such as chitinous jaws
and rough elytra have other means of self protection. If Nephthy-
didae, Nemertidae, or Phyllodocidae are attacked by other annelids or
are disturbed in some other way, they immediately protrude the pro-
boscis, extruding a slimy substance which evidently must be disagree-
able to their aggressors, for the latter immediately withdraw.

The abundance or seareity of food undoubtedly plays an important
role in the distribution of polynoids, so that one would naturally expect
to find the worms more abundantly represented in localities where the
food is at the maximum. The constitution of the bottom may deter-
mine the annelid population. It has been observed that some Poly-
noidae, and Annelida in general, oceur in a depth of 14 fathoms in
Kiel Bay, while the same species are found off the Faroes in 60 to 100
fathoms. Again, some species occur in great abundance on the shores
of Greenland and Denmark at a depth of 6 to 10 fathoms, while around
the Faroes they are only scantily represented at a depth of 60 fathoms.
The cause of this difference in bathymetric distribution has been attri-
buted to the differences in the constitution of the bottom. The shores
of the Faroe Islands are rocky and steep, and the soft, muddy bottom

AA University of California Publications in Zoology [Vou. 18

is found some distance away from the shores, while in other places
the bottom nearer shore is muddy and soft (Willemoes-Suhm, 1874).
The best feeding grounds of the oceanic fauna are undoubtedly the
shore regions or littoral zone, where plant and animal life occurs in
great abundance. Hence the Polynoidae and annelids in general are
more abundant in the littoral zone. With an increase in distance
from the shore and with an increase in the depth there is a decrease
in individual numbers of the Polynoidae but a proportionate increase
in genera and species. On this coast, although the littoral Polynoidae
are very abundant so far as individual numbers are concerned, yet
there are only four genera and fifteen species (table 4). Of these
four genera, one, Hunoé, is not common in subtropical littoral zones but
occurs as a littoral form in the boreal and subboreal regions, and as
an abyssal form in the temperate and subtropical zones. This leaves
only two strictly littoral genera in the subtropical and temperate zones.
Of the exclusively deeper water polynoids we have seven genera and
fourteen species. The number of deep water genera is about two
times that of the littoral polynoids, and the number of species about
equal. The number of individuals, however, is very small, and some
deep water genera are known from but a single representative.
Although we have to admit that the deep water survey is less com-
plete than that along the shore, nevertheless the data show that there
is an increase in genera with an increase in depth, and that the great-
est uniformity prevails among the littoral polynoids. The species
most abundantly represented on this coast, such as Halosydna insignis,
H. californica, H. carinata and H. interrupta, are very much alike in
their general appearance so that by superficial observation they are
more likely to be taken as individuals of the same species. The same
similarity may be observed among other species and genera and great
diversity of species and genera found among the deep water species
is not as common among the littoral species. Food conditions near
the shore aid to increase and multiply the lttoral polynoids. On the
other hand, the scanty food supply in the depths, other things being
equal, will naturally check the increase of the deep water polynoids.
The deep water species of Polynoidae evidently do not inhabit the
depths from choice, but many of them have been carried from the
colder boreal regions and have found there identical temperature con-
ditions although the food conditions are greatly different. Other
polynoids have been driven off shore by waves or storms. Secondly,
since the food supply in the great depths is insufficient only com-

1918 | Essenberg: Distribution of the Polynoidae 213

paratively few animals can exist on a given area, while an area
similar in size but with abundant food supply nearer shore naturally
contains an abundance of animals.

Aside from the problem of food supply the mode of life of the
Polynoidae deserves some consideration. The majority of the Poly-
noidae are free living forms and the largest numbers, as has been
indicated above, are found near the shores and between tide marks
where they hide in crevices and beneath rocks, pebbles and weeds or
crawl about freely. Most probably they do not go very far from
their dwelling place unless driven away by some physical force.

There are, however, some polynoids which depend for their dis-
tribution on the locomotion and the mode of life of other animals.
These are the commensal forms. The number of strictly commensal
species known up to present time is limited. Nevertheless, some
species are known exclusively as commensals and depend for their
distribution on their messmates; hence their distribution naturally
coincides with that of the latter. These commensal polynoids are:
Lepidasthenia gigas, commensal with a large tube dwelling annelid,
Amphitrite; Polynoé lordi, commensal with the limpet, Glyphis aspera
and with Cryptochiton stelleri, in which it occupies the branchial
groove; Polynoé fragilis, commensal with the starfish, Asterias
ochracea. These species are known up to the present time only as
commensals, and have a very limited distribution. A few other species
occur both as free living forms and occasionally as commensals. Those
known on this coast are: Halosydna insignis, Polynoé californica and
Harmothoé imbricata. These species do not necessarily depend on
their messmates since they live both as commensals and independently.
They are most widely distributed on this coast. Evidently the ability
to live in a variety of environments favors the wide distribution of
these polynoids. The known facts and the observations lead one to
the conclusion that the food habits, food supply and the mode of hfe
play an important role in determining the distribution of the Poly-
noidae.

VII. Puasticity

Some of the most obvious external factors controlling distribution
have been enumerated. But there may be other factors of a more
complex nature, which are beyond our present reach and are waiting
for future investigations. There is, however, one more factor, viz.,
variability. Variability or plasticity may be considered both as a

214 University of California Publications in Zoology [Vou. 18

factor and a result of distribution. As a factor, because species with
greater plasticity and greater power of adaptation are able to live
in a great variety of environments, and consequently have more
chance to survive than have species with a very limited power of
adaptation. Some phases of variation serve directly as a protection
to the animal. Other forms of variation are usually results of environ-
ment. It is the expression of a varied mode of life, or a response to
external stimuli. This has been variously proved by experimental
methods, where variations are produced artificially by changing the
environment. Not all living organisms, however, respond to the
same external stimuli in the same way. While one form of animal
hfe may undergo considerable changes under the influence of external
stimuli, others, being unable to adapt themselves to new conditions,
will perish. This is shown in Loeb’s experiments with the eggs and
the embryos of Fundulus referred to above. While a great percentage
of the embryos were killed after four to seven hours exposure to low
temperature, others remained alive, and among the latter 30 per cent
were abnormal. This indicates that there is a difference in plasticity
or in the power of adaptation even among different individuals in the
same species. In sudden changes of environment the power of adapta-
tion will determine the survival and, consequently, the distribution of
a species or an individual.

Numerous instances of great adaptation are known among various
organisms signifying that the animals have an innate power which
enables them to resist adverse conditions. This power is designated
as plasticity or adaptability. The degree of plasticity varies in differ-
ent species and individuals. Hence as the distribution depends to
some extent on the power of the adaptation of the animals to the
changing environment, the plasticity may be justly considered as a
factor determining the distribution.

From the observations made, one comes to the conclusion that the
plasticity in Polynoidae, although varying in degree in the different
species, is fairly great in most. Marked differences between different
genera and species are found among polynoids characterizing their
mode of life and the influence of the environment upon them. These
differences occur in the size, the shape and the color of the body, in
the size, shape, texture and color of the elytra, in the number, shape
and size of the setae, in the texture of the cuticle, and in other char-
acteristics. These variations occur not only in different species but
individuals of the same species which are living in different environ-

1918 | Essenberg: Distribution of the Polynoidae 215

ments show such marked differences that they appear more like differ-
ent species than individuals of the same species.

It is generally known that of the cosmopolitan polynoids occupying
different latitudes, the arctic examples as a rule are larger in size
than are those of the temperate or subtropical zones. Lepidonotus
squamatus exhibits a characteristic difference in size among indi-
viduals from different localities. Comparing the specimens of that
species from Finmark, New England, Puget Sound and from the
coast of California, great differences in size appear. The size of the
specimens from the coast of California is about one-third of that of
the specimens from Finmark and New England. The specimens from
Puget Sound are considerably larger than are the Californian but
they are inferior in size to the arctic and eastern forms. Ehlers
(1875) found also that the deep water forms were considerably
smaller and that they have thinner elytra. A further influence of the
depth on the polynoids is seen in the lack of pigmentation and the
eyeless condition of the worms. A great number of the deep water
polynoids are without eyes. Moore (1910) enumerates eight blind
deep water species of Polynoidae on this coast. Of all the numerous
polynoids in this collection, however, not a single specimen of the
littoral species of this coast is eyeless. Ehlers (1875) believed that
it is natural for the deep water annelids to be blind since many of
the deep sea species have been found in that condition. He accounts
for the possibility of some deep water individuals having eyes as due
to the yearly migration of littoral forms toward greater depths.

The influence of the environment on the organisms is here very
marked. Considering the environmental differences in shallow and
deep oceanic waters, one will naturally expect to find the correspond-
ing physical changes in Polynoidae. Besides the minimum food con-
ditions in the great depths and the different chemical composition of
the water, the pressure in great depths is very much greater than in
the shallow waters, for it is a well known fact that the pressure in
the ocean increases by about one atmosphere for every ten meters in
depth ; consequently in a depth of about 2,000 meters (1,000 fathoms)
there is a pressure of 200 atmospheres. It has also been proved by
various hydrographers (e.g., Murray, 1912) that there is no light in
the oceanic depths below 500 fathoms. On the brightest day and in
the clearest and most transparent waters only slight traces of the
blue light rays are perceptible at a depth of 1,000 meters. The green
rays are absent at a depth of 500 meters, the red rays are absorbed by

216 University of California Publications in Zoology (Vou. 18

the surface layers without penetrating even to a depth of 100 meters.
There is an absolute darkness in the depths below 1,000 meters. Add-
ing these combined factors to the low temperature, insufficient food
supply, the small quantity of free oxygen, and carbon dioxide are
sufficient causes to bring about variations and changes in abyssal
Polynoidae.

The effect of the environment on the Polynoidae and the great
plasticity of the latter is especially noted in commensal polynoids.
The variation in size between the commensals and free-living forms
of the same species is remarkable in some cases. Halosydna insignis
is a beautiful example of this variation. This species is known as a
free-living form occurring in a variety of environments; it also
lives as a commensal in the tubes of Amphitrite and Thelepus. The
species is widely distributed, occurring along the entire coast of
North America. The commensal individuals are longer and more
rounded. The elytra are thinner and, excepting the first pair, devoid
of marginal cilia. They are smaller and do not cover the entire
dorsum. The spinous tuberecules on the elytra are very much reduced
and are almost microscopic in size (pl. 8, fig. 27). The dorsalmost
setae are greatly enlarged and bear an enlarged spur. The neural
setae are stouter and strongly hooked. The free-living specimens are
broader and shorter and usually smaller in size than the commensals.
The elytra are thicker, tougher and larger, strongly overlapping and
covering the entire dorsal surface (pl. 8, figs. 28-30). They are
thickly. covered with large, horny prickles and bulbs. The marginal
cilia are longer than they are in commensals and are present on all
elytra; there is also a tuft of long cilia arising a short distance from
the anterior margin. The setae are more slender, less strongly hooked,
and with fewer serrations. The pigmentation is stronger in com-
mensals than in free-living examples. But the pigmentation varies
considerably in both kinds. From all the characteristic differences |
indicated the two forms are very likely to be taken for different
species rather than for members of the same species; however, these
characteristic differences in the commensal and free-living Halosydna
insignis illustrate the great plasticity in that species of polynoids and
the influence of the environment upon it. Thrusting itself into a
tube of a messmate the polynoid does not naturally find the tube made
to fit the shape of its body, and if it were not for the great plasticity
of the creature it would perish in the tube if it did not soon leave it.
But here comes nature to assist the intruder in adapting itself to its

1918 | Essenberg: Distribution of the Polynoidae 217

new environment. A muscular adaptation occurs. The muscles, espe-
cially those in connection with locomotion supporting the parapodia,
are constantly used by the free-living worm and through this exercise
they are naturally well developed. In a commensal polynoid the
locomotor muscles are of no use and begin to degenerate. Secondly,
the dwelling place is too narrow and the walls of the tube press upon
the broad lateral surfaces. This constant pressure forces the muscles
to contract laterally and to expand ventrally, dorsally and longi-
tudinally where no pressure or resistance is met. If the commensal
polynoid remains in this condition for some time, the shape of its
body will naturally be changed from a compressed flat one to a
rounded one. The elongation of the segments will increase the length
of the worm, the parapodia become shorter and broader and we have
a worm that has changed its shape so greatly that it could hardly be
recognized as being an individual of the species.

That Polynoidae tend to retain the plasticity, which is common to
some higher types in the very early stage of development, is proved
by the great power of regeneration which they possess throughout
their lives. If a polynoid loses some of its segments, elytra or append-
ages, it regenerates them within a few weeks. This is an indication of
plasticity and adaptability to diverse conditions.

The changes of color are probably produced by some enzymes pro-
duced by the messmate of the commensal polynoid. The small size of
the elytra is evidently due to the disuse and the degeneration of those
structures. The absence of the chitinous bulbs and protuberances on
the elytra may be accounted for in the same way. First, the free-
living polynoid is under the influence of some chemicals which act as
stimulants in the production of the bulbs on the elytra. Living as
a commensal its environment has been changed and the secretions or
enzymes of the messmate may impede the development of the rough
structures on the scales of the polynoid. That this is true is proved
by the fact that the first pair of elytra remain unchanged. The
reason for this condition is apparent. The polynoid is hidden in the
tube with its anterior end, its tentacles and head projecting. The
first pair of elytra remain in the same environment in the open water
as they were before the polynoid entered the tube hence they remain
unchanged. The external changes in this case may be traced back
to the changes of environment and to the quick response or the plas-
ticity of the polynoid undergoing these changes.

218 University of California Publications in Zoology [Vou 18

That the environment and adaptation may lead to some extreme
variations is illustrated by the shape of Polynoé ocellata. This species
has been recorded from Japan (MeIntosh, 1900; Izuka, 1912) as a
commensal, living in the tubes of Spirochactopterus challengeria.
The worm is extremely elongated and narrow, having over one hun-
dred segments and fifty or more pairs of elytra. The length of the
worm is about 60 mm. but its breadth is only 2.5 mm., including
setae. It is most vividly colored with yellow, olive, black and white
markings. The elytra are exceedingly small, translucent and smooth.
The first pair of elytra, however, are large, covering the prostomium
completely ; they are also less delicate. In a vertical section, McIntosh
discovered that the cuticle and hypodermis of the worm are unusually
thin. This again illustrates the great variability and the power of
adaptation of this polynoid. It is remarkable that the external
changes do not occur uniformly but that parts subjected to somewhat
different environment, as the anterior elytra, which are naturally
outside of the tube and are exposed to the free ocean water, differ in
size and structure.

As far as is known it may be considered as a general rule that
the commensals are usually larger in size than the free-living indi-
viduals of the same species, provided the dwelling place of the com-
mensal is sufficiently large so as not to interfere with the expansion
of its body. Polynoé californica is known as both commensal and
as free-living. The commensal animals are noted for their large size,
while the free-living individuals collected from various places are
much smaller. All the largest specimens, except one from Santa
Catalina, were collected near San Pedro. They range from 35 to 45
mm. in length and from 8 to 14 mm. in breadth. The specimens from
other localities have a size ranging from 15 to 30 mm. in length and
from 5 to 11 mm. in breadth. The average length of the worm is
about 25 mm. Johnson (1897) states that the species has been found
on a huge Amphitrite off San Pedro. That the commensal forms of
Polynoidae are usually larger in size, relatively and absolutely, can
be proved by the fact that not only individuals of the same species
distinguish themselves through their larger size from the free-living
specimens, but that species which are known exclusively as commensals
are of relatively greater size. Thus the largest species in the family,
Lepidasthenia gigas, is a commensal with an amphitrite. The largest
specimens measure 180 mm. in length, and 7.5 mm. in width. It would
be a far-reaching conclusion to assume that Lepidasthenia gigas has

1918 | Essenberg: Distribution of the Polynoidae 219

reached its large size because of its commensalistic habits, but it is
very likely that the commensalistic habit aids it In maintaining its
large size. The commensal habits evidently are of some advantage
to the polynoids favoring their growth and development. One advan-
tage is that the commensals do not have to exert as much energy to
obtain their food as do the free-living worms. In thickly populated
places the competition among animals must be considerable, hence an
animal must exert a great amount of energy in changing location and
in pursuit of prey. At the same time it has to be vigilant in guarding
its own safety lest it fall a victim to other animals. The free-living
Polynoidae usually are found beneath rocks or weeds or in crevices.
Occasionally they venture out of their hiding place, but the least dis-
turbance causes them to disappear again. Their great activity will
naturally reduce the volume of the body or check its development.
On the other hand, the commensal does not have to exert any energy.
It is well protected and leads a passive life. Secondly, it obtains an
abundant food supply. The writer has watched some of the tube-
dwelling annelids many times. They reach out their numerous ten-
tacles in great distance forming a circle and capturing any object
within their reach conveying it then to the mouth. It is surprising
to see the amount of food and material they may convey to the tube.
Once the writer destroyed the tube of some tube-dwelling annelids,
erumbling it carefully to pieces without injuring the worms which
were then put into a small glass dish where the material of their
tubes had been crumbled up in fine granules. The worms immediately
set to work with their tentacles rolling the small pebbles and the
grains of sand toward their bodies and cementing them with some
substance which was formed around the body. Within less than two
hours the tubes, about two inches in length, were completed. If a
terebellid worm is placed in an aquarium where the food supply is
insufficient it stretches out its long tentacles covering considerable
distance. The tentacles when stretched to the limit are about equal
in length to the body of the worm. As soon as one of the tentacles
comes in contact with some substance or food particles it immediately
contracts and bends, conveying that substance to the mouth. If the
polynoid is in the tube with its head at the entrance it may capture
every food particle that is conveyed toward the tube, robbing thus
its messmate of its food and receiving an abundance of food for itself,
at the same time remaining perfectly quiet. This passive condition
and the abundant food supply will naturally result in an increase in

220 University of California Publications in Zoology | Vou. 18

the size of the body. Commensals that live on the surface of moving
animals have the same advantage. While the food is not carried
directly to their mouths, the polynoid however is carried to new feed-
ing grounds and no energy is used in locomotion. Hence there is less
chance for reduction of the size of the body. Moreover, the polynoid
may become an ectoparasite, obtaining some of its food directly from
its messmate. It has been found that some Polynoidae living on
sponges had in their digestive tracts spicules of the sponges on which
they lived. This proves that they are feeding on their hosts. They
may become ectoparasites on other animals in a similar manner, con-
suming some of the secretions or part of the food of their hosts.

Another interesting feature is the adaptive coloration in Poly-
noidae. This evidently is the result of the environment. Such an
example remarkable for its adaptive coloration is Polynoé pulchra.
The worm is commensal with two animals, the sea eucumber, Holo-
thuria californica, and the keyhole limpet, Lucapina crenulata. Laiv-
ing specimens from both hosts were given to me for identification.
Judging from the color they look more like different species than indi-
viduals of the same species. Only microscopical examination reveals
the identical specific characteristics of both. The example living on
the holothurian mimics the color of the latter to perfection and can be
hardly detected when it lies quietly on the surface of its host. The
polynoids occupying the cavity between the mantle flap and the foot
of the limpet are very conspicuously colored, with prominent black
markings which show plainly against the uniformly colored, whitish
yellow background of the ventral surface of the limpet.

Another example of a polynoid showing great adaptive coloration
is Polynoé fragilis. This species lives in the ambulacral groove of the
starfish, Asterias ochracea and Asterias trochelu. Johnson (1897)
had an opportunity to observe the polynoid on the aboral side of the
starfish where its coloration harmonized so well with that of the
Asterias that it eseaped any notice. The elytra of this polynoid also
are thin and delicate, without any tubercles or prominenees, and cov-
ering the dorsum only partly (pl. 8, fig. 32). A remarkable adapta-
tion is also seen in the setae (pl. 7, fig. 14). The latter are few,
slender, pointed and hooked, being thus well adapted for attachment.
Moreover, the setae as they become blunt from wear are continually
replaced by new pointed ones growing out from the base of the para-
podia (pl. 7, fig. 15). The latter characteristic is not common to all
Polynoidae but is an exception observed in a few species which are in
a habit of attaching themselves to other animals.

1918 | Essenberg: Distribution of the Polynoidae See

MelIntosh (1900) has observed a remarkable variation in Polynoe
scolopendrina. This worm lives as a commensal and as a free-living
form around the shores of England and off the Hebrides. Besides
the remarkable differences in size between the free-lving and com-
mensal forms from the shores of Great Britain and the individuals
off the Hebrides there is a difference in coloration particular to each
group. The coloration is especially conspicuous in the commensals
oceupying the burrows of Lysidice. The commensal, according to
MeIntosh’s observation, is very narrowly compressed. The pigmenta-
tion of the anterior ventral portion of the body of the worm and
around the mouth has a coloration mimicking the Lysidice. The tube-
dwelling Polynoé scolopendrina have the setae greatly modified ; espe-
cially is this true of the dorsal setae, the tips of which are curiously
wrinkled. The specimens from the Hebrides, however, prove that
in the normal conditions the setae are finely tapered. The wrinkled
condition has evidently been brought about through the commensal
life.

E. GENERAL DISCUSSION

The fact that Polynoidae fall into different groups according to
their geographical and bathymetrical distribution suggests that the
phenomenon of distribution is governed by certain physical and
chemical factors and that the Polynoidae, reacting in response to
the external stimuli, are limited to their particular distributional
areas.

One of the most important factors controlling distribution is the
temperature. This is proved by the fact that certain species of Poly-
noidae are limited to definite temperature zones, and that boreal
species, occupying the littoral zone, occur as deep water species in
temperate and in subtropical zones. Since the most apparent simi-
larity between the boreal shallow waters and the subtropical deep
waters consists in the temperature, this latter may be considered as
the chief factor in distribution. Other factors, as currents and winds,
may act in transportation of the larval and adult forms or by influenc-
ing the temperature and the food conditions.

The food conditions may be of importance in distribution and
polynoids may be naturally expected to be more abundant where food
conditions are maximum. This condition is found in the littoral zones.

222, University of California Publications in Zoology (Vou. 18

The greatest number of polynoids is found in the littoral zones. The
number of polynoids decreases with the increase in depth. On the
other hand, a greater uniformity prevails among the littoral poly-
noids. The number of genera and species increases with the increase
in depth so that the deep water genera of this coast are almost two
times the number of the littoral, and the deep water species are almost
equal to the number of the littoral. This condition seems to indicate
that the littoral zone is the center of origin of the Polynoidae and
that they have migrated or have been driven occasionally from the
littoral zones to the deep water where they have probably under-
gone considerable external changes, forming thus new genera and
species, while the shallow water forms living in the same environment
have maintained a greater uniformity. Moreover, the different
environment in the greath depths, as the low temperature, the absence
of light, the difference in chemical composition of the water, may
produce a semipathologic condition in the polynoids affecting the
germ cells, and thus bring about rapid changes and partial degenera-
tion. This is suggested by the great degenerative changes found in
the deep water polynoids. The deep water species, as compared with
the littoral species, are as a rule smaller in size, and have delicate
euticle and elytra. A great number of the deep water species are
without eyes. On this coast out of fourteen abyssal species eight are
known to be without eyes (Moore, 1910). This shows that the deep
water species have undergone certain physiological and morphological
specialization in adapting themselves to their particular environment.
This special adaptation or the degenerate condition, however, makes
them unfit to adapt themselves to any other environment. The low
temperature in the depths of the ocean undoubtedly has a great effect
upon the developing annelid eggs in producing abnormalities and
physical variations. This assumption is in aecord with the laboratory
experiments where abnormalities, such as blindness and other defects,
are produced artificially by subjecting eggs in their early stages of
development to a low temperature. Secondly, the embryos may be
affected by the sudden environmental changes or by the shock effect
of the sudden change of temperature. The annelid trochophores
rising from great depths to the surface would naturally come sud-
denly into a very much higher temperature which would kill the
majority of them or would modify them greatly. In the littoral zones
where the difference between the bottom and surface temperatures is
less conspicuous, the worms in their embryonal development are not

1918 | Essenberg: Distribution of the Polynoidae 223

subject to the sudden environmental changes and are less likely to
be killed by the temperature or to undergo any variation and abnor-
malities.

There is a general belief that the deep water annelids are without
eyes or blind on account of the absence of the light in the great depths.
Experiments in the laboratory have proved that absence of light does

- not produce blindness, but on the other hand by exposing eggs to 0

to 2° temperature, numerous abnormalities and blindness in embryos
of the fish Fundulus were produced (Loeb, 1915). Since the corre-
sponding low temperature is found in the depths of the ocean it would
not be at all unlikely that the low temperature, although it may not
change the adult forms which have been carried from warmer areas to
the cold waters in the depth, may still affect the second generation—
the eggs of the first migrants—and thus produce blindness indirectly.
So that the cause of blindness and eyeless condition of the abyssal
Polynoidae might be attributed to low temperature rather than to
darkness.

The degree of light intensity may be a cause of modification of
the eyes of deep sea animals. It has been found (Brauer, 1901) that
in all fish from about 300 meters, the rods only are found in the retina
of the eye, a condition which is characteristic also of the eyes of
nocturnal animals; while diurnal animals have both rods and cones.
The differences of the pigment of the retina in the deep sea fish signify
that their eyes are adapted to nocturnal conditions. Further result
of the modification and adaptation is the telescopic eyes of some fish.
There are also great numbers of blind fish in the depths of the ocean ;
it remains an open question whether the blindness is caused by the
low temperature or by the action of some chemicals in the deep sea or
by a combination of both.

That the plasticity is great in Polynoidae is proved by the fact
that considerable changes are produced. A remarkable difference
is noticeable in the size and shape of different individuals living in’
different environment. Boreal species as a rule attain a larger size
than individuals of the same species occurring in tropical and tem-
perate zones. This rule of comparative size within a given species
does not hold strictly true as between localized species. The largest
known polynoid, Lepidasthenia gigas, is subtropical, inhabiting a
limited area on the coast of southern California. It is quite possible,
however, that its great size is an unusual development since the
animal is an exclusive commensal.

224 University of California Publications in Zoology {Vor 18

The greatest variation and plasticity is seen in the commensal
polynoids. As a general rule the commensals are larger in size than
the free-living individuals of the same species. This fact is un-
doubtedly due to the greater food supply which a commensal obtains
by robbing its messmate of the food which the latter has secured,
or the commensal may become an ectoparasite as has been observed
to be the case with some polynoids living on sponges. In examining
the contents of the stomachs of polynoids (Darboux, 1899) spicules
of sponges were found indicating that the commensals had been feed-
ing on their messmates. Secondly, a commensal is protected by the
messmate by living in the tube or hiding in some sheltered place of
the body of the latter. Since it lives there in absolute quiescence
there is less catabolism in its organism than in the free-living worm
which has to exert a great deal of its energy in securing food and in
watching for its own safety. Consequently almost the whole food
supply of the commensal goes to build up and to increase the bulk
of the body, and the natural result is the larger size of body which has
been mentioned above.

Moreover, the shape of the body of the commensals may be greatly
modified by an increase in length, and by reduction in breadth, thus
changing from a short, compressed to a long, round form. The pro-
tective structures in commensals, as the elytra, the cuticle and the
setae, are usually degenerate.

A marked adaptive variation is noticeable in the number, strue-
ture and size of the setae according to the mode of life of the com-
mensal. In the free-living species the setae are numerous, usually
from 50 to 100 on each parapodium (pl. 7, figs. 1, 19). The setae
in the free-living species are also rougher, with numerous, strong
serrations (pl. 7, figs. 4-6, 8-11). In commensals and ectoparasites,
especially in those which are in the habit of attaching themselves to
their hosts, the number of setae is greatly reduced (pl. 7, figs. 15,
17). Some species, as Polynoé pulchra and Polynoé lordi, have only
5 or 6 slender, -smooth, sharply pointed setae, the blunted setae being
constantly replaced by new, sharply pointed ones which arise from
the base of the parapodium (pl. 7, figs. 3, 7). In some of the tube-
dwelling commensals, as Lepidasthenia gigas, the number of the setae
is small, usually 5 to 8 on each parapodium. The setae (pl. 7, fig. 13)
have a few serrations and are not so sharply pointed as are those in
the commensals which use their setae for attachment to their host.
In Lepidasthenia gigas, however, there is, in addition to the ordinary

1918] Essenberg: Distribution of the Polynoidae 225

setae, a strongly developed dorsal neuro-seta (pl. 7, fig. 18) peculiar
to that species only. Whether it has any significance in the com-
mensalistie life of that polynoid is an open question. Whether the
reduction of setae is a secondary characteristic developed in response
to commensalistic life, or whether the polynoids chose that mode of
life because of the fitness of their setae for that purpose, is another
question which cannot be definitely settled at present. However, the
sharply pointed and hooked setae are of special use to the polynoid
as a means of attachment to the host.

One phase of plasticity in polynoids reveals itself in the variation
of color in response to different environments. In the majority of
eases the abyssal forms are less brightly colored. The commensals
and ectoparasites, however, display a great variation in color, as 1s
seen in some species which occur simultaneously on two or more differ-
ent hosts. For example, Polynoé pulchra, which lives on Lucapina
crenulata hidden between the foot and the mantle flap of the latter,
is very conspicuously colored, while individuals of the same species
found on holothurians, completely mimic the color of the latter.

Such changes in color may be due to various causes but in each
case are evidently caused in response to some chemical or physical
stimulus. The color in each animal indicates that there is some
chemical reaction particular to that species. With changes in the
environment the physical equilibrium is disturbed and some chemical
affinities may be more stimulated to reaction than others. These
changes may induce new interactions in the tissue and protoplasm of
the animal, resulting in external changes, such as changes in color.
Polynoidae in great depths are, as a rule, less strongly pigmented or
entirely unpigmented. This fact shows that there is some inhibitory
action which prevents the pigment from forming. Whether it is the
absence of light, the different chemical composition of the water, or
the low temperature that produces the changes in color cannot be
definitely decided. It has been proved by experimental methods that
no pigment was produced in the chrysomelid beetles when the embryos
were kept in low temperature (0° to 5°C) while embryos kept in high
temperature (43° to 45°C) developed dark pigment (Tower, 1906).
Since pigmentation involves the process of oxidation or metabolism,
the temperature undoubtedly is an important agent in accelerating
or retarding the development of color. Furthermore, the light intens-
ity may be of some importance in production of color. However, the
light reaction seems to be of secondary importance as is shown in the

226 University of California Publications in Zoology [Vou.18

fact that some commensal worms, such as Polynoé pulchra living on
the keyhole hmpet between the foot and the mantle of the latter, and
protected from the light, are conspicuously colored. The same has
been observed to be true with Polynoé ocellata, which lives as a com-
mensal in tubes, sheltered from light, yet is very vividly colored.

The so-called color mimicry in Polynoidae may be due to chemical
responses or to stimulating enzymes. The commensals living in close
contact with their messmates probably have a chemical inter-relation
with the latter, and are influenced by some of the same chemical con-
ditions which are responsible for the color production in the latter.
Under a similar chemical or enzymic reaction the same color pattern
is produced in the commensal polynoid. This may be a plausible
explanation of how commensal polynoids adopt the color pattern of
their messmates to such perfection as is shown in Polynoé pulchra
living on the holothurian, and Polynoé scolopendrina living in the
tube of the Lysidice, both mimicking the color of their messmates.
These facts seem to lead to the conclusion that there must be some
chemical interaction between the two commensal species stimulating
the latent chemical and protoplasmic properties of the worm to color
production. That animals can be stimulated to produce colors has
been proved experimentally by extracting the pigment-producing
enzymes from beetles and placing parts of other unpigmented beetles
in the extracted enzymes, with the result that pigment was produced
on the unpigmented beetle (Tower, 1906). Evidently some influence
must be exerted by the enzymes of the host on the commensal worms
and the chemical complexes which are present in the protoplasm of
the commensal, when stimulated in the polynoid, will react in a definite
manner, producing similar colors to those of the host.

The great differences in coloration between Polynoé pulchra living
on the keyhole limpet, and the one living on the holothurian may be
explained on the basis that although the former is living in the mantle
fold of the limpet in an area which shows no pigmentation, yet the
pigment-producing enzymes are probably present in other parts of
the body of the mollusk. The cells of the lower surface of the latter
may not have the base, or the color-producing properties and hence
do not respond to the stimulus of the enzyme, while the protoplasm of
the polynoid possesses the color producing properties which are latent.
As soon as they receive the proper stimulus, they react and the dark
brown or black pigment, similar to that found on the upper surface
of the mollusk, is produced in certain areas of the elytra of the poly-

1918} Essenberg: Distribution of the Polynoidae 227

noid. The color producing enzyme may be obtained by the polynoid
either by partly feeding on its host or the enzyme may be given off
the mollusk in some kind of secretion. There may be still another
possibility, viz., that both the commensal and the mollusk are obtain-
ing the same kind of food and that this food may act as stimulant in
producing the same colors. Yet food alone could not be responsible
for the color production ; it may be only one of the agencies concerned
in color production, else the pigment would be distributed more or
less equally over the entire body. Cases are known, however, as in
Polynoé scolopendrina (MeIntosh, 1900) in which dark brown pig-
ment is produced only around the mouth and the anterior ventral
region, giving that part of the body the general appearance of Lysidice
whose tube the polynoid occupies. The rest of the body is, however,
less affected by the color. Be it the similar food conditions, or the
influence of some enzymes that produce the same combination of colors
in the holothurian and in the polynoid, and another color pattern in
the mollusk and in the polynoid, it is evident that the same forces
which act on the messmates in producing a certain color pattern do
act on the commensal polynoids producing the same results. The
significance here les in the fact that animals widely different in the
scale of evolution possess the same properties which when aroused by
similar stimuli respond in the same way producing similar results in
pigmentation.

Other external changes in commensals may be caused by the various
environmental influences in response to the plasticity of the animal.
The close contact with the messmates, probably through the secre-
tions and enzymes of the latter, may react variously on the commensal,
weakening the external structures such as the cuticle and elytra, so
that they gradually degenerate (pl. 8, figs. 27, 31) or assume a more
delicate texture like that of the messmate. The abundant food supply
which the commensal obtains and the lack of exercise aid in increas-
ing the bulk of the body, while the limited space in a tube aids in
shaping the body, thus entirely changing the external appearance
of the commensal. This suggests the possibility that a species, if
subjected to similar environmental conditions for generations may
change its characteristics and become a new variety or a new species.
In our well known Halosydna insignis, the free-living and the com-
mensal may become two distinct varieties, if not distinct species, if kept
in their corresponding environments for generations. These observa-
tions suggest the possibility that the environment and a corresponding

228 University of California Publications in Zoology [Vou 18

plasticity may result in formation of new species. They further sug-
gest the possibility that different species occupying different geo-
graphical and bathymetrical areas are descendants from common
ancestral stocks and that their differences are the results of the par-
ticular external influences and of the degree of plasticity in each
species. Species with the greatest plasticity are best provided with
protective structures and are more widely distributed. Being able
to overcome vicissitudes and changes in environment, they are superior
to species specialized for certain modes of life and for certain environ-
ments. Lepidonotus squamatus serves as a good illustration. It has
rough spiny elytra (pl. 8, figs. 834-35) covering the entire dorsum,
and numerous strongly developed setae (pl. 7, figs. 8-11). On one
oceasion MeIntosh (1900) observed that a specimen of Lepidonotus
squamatus which was in a tank with other animals was coiled up so
as to have its scales and setae placed to the best advantage for self
protection. When it was picked up by a young cod it was immediately
rejected and fell to the bottom. Again it was attacked by Cottus, and
again also immediately rejected, while Nereis and other annelids were
devoured by the same animals. This explains partly the world wide
distribution of Lepidonotus squamatus while the largest species of the
family, Lepidasthenia gigas, depending entirely on a commensalistic
life and being ill protected outside of the tube, has a very limited dis-
tribution. Probably young Lepidasthenia gigas fall victims to their
enemies if they do not happen to find a vacant tube of an Amphitrite ;
or their adaptability is so limited that they can live only in that
particular environment as commensals and perish in open ocean.
Hence there are no free-living forms of that species. These facts
show that, besides the external factors, the physical condition of the
animal, its powers of adaptation, and its variability are equally impor-
tant factors in its distribution.

1918] Essenberg: Distribution of the Polynoidae 229

F. SUMMARY

1. Polynoidae as a group have a world wide distribution, occurring
in all oceanic waters. The fifty-one species of Polynoidae on this
coast are divisible into two main divisions: (1) the cosmopolitan, and
(2) the non-cosmopolitan species. The cosmopolitan species occur
in all oceans; the non-cosmopolitan are restricted to the Pacific Ocean
and many of them occur only along the shores of North America.

2. The Pacific coast polynoids, on the basis of their geographical
distribution, fall into boreal, north temperate, and subtropical species,
according to the life zones they occupy.

3. The polynoids are again divisible into littoral, sublittoral, and
abyssal species according to their bathymetrical distribution.

4. The distribution of Polynoidae is evidently controlled by certain
factors. The most important factors determining distribution are:
(a) temperature, (b) currents, (c) winds, (d) chemical composition
of water, (e) food habits and mode of life, and (f) plasticity or
response of the animal to its environment.

5. The facts that certain species are restricted to definite life zones
and to definite ranges of temperatures, that the same species occurring
in widely separated areas occur in depths of similar temperature and
that boreal species occur in temperate and subtropical zones as deep
water species, seem to point to the conclusion that temperature is the
chief factor in determining distribution.

6. Some species of Polynoidae are found in widely separated areas.
Since they cannot possibly traverse such distances by their natural
means of locomotion, currents may be regarded as agents in distribu-
tion, carrying the adult worms along the bottom and the pelagic
larvae in the upper strata and at the surface. The currents may
further influence the temperature and the food conditions of an area.
Consequently they play an important role in determining distribution.

7. After severe storms some deep water species are usually found
driven to the shores. The winds may thus serve as agents in determin-
ing distribution.

8. The chemical composition of waters differs at different depths
and latitudes. Since. certain species of polynoids are restricted to
definite areas and to definite depths, undergoing there considerable
external changes, the chemical composition of water may be of some
importance in determining distribution.

230 University of California Publications in Zoology [Vou.18

9. The greatest numbers of polynoids are found in the littoral zones
where food is more abundant. Hence the food conditions of a certain
area may be of some importance in controlling distribution. The mode
of life may also influence the distribution. This would be especially
true of commensal polynoids. Their distribution would naturally
depend on that of their messmates.

10. Modifications and changes in the polynoids are considerable.
These changes are marked in size, shape and color of the body, in the
size, shape, structure and color of the elytra, in the number, shape,
size and structure of the setae, and in the texture of the cuticle. These
changes are remarkable in commensal polynoids, so that commensal
individuals differ greatly from the free-living forms of the same species
in all the characteristics enumerated above. The deep water species
differ considerably from the littoral species and certain characteristies,
such as the thin cuticle, the smaller size, the delicate elytra and eye-
less condition of many abyssal species, point to the conclusion that the
latter have undergone a degeneration and a physical specialization
which makes them fit for that particular environment only. Such
changes, however, would be impossible if the polynoids did not possess
a plasticity and were not able to react in response to the external
stimuli. The plasticity may be therefore, regarded as one of the most
important factors in controlling distribution.

11. The perfect color mimicry of the commensal polynoids sug-
gests that there is some chemical or enzymic interaction between the
messmates and the commensal, producing similar color patterns in
animals widely different in kind.

12. The great uniformity of littoral species and the great diversity
of abyssal genera and species lead to the conclusion that the lttoral
zone is the center of origin, or the center of dispersal of the polynoids,
and that species migrate or are driven to abyssal areas where they
undergo great specialization and partial degeneration.

1918] Essenberg: Distribution of the Polynoidae 231

LITERATURE CITED

BRAUvER, A. G.
1901. Ueber einige von der Valdivia-Expedition gesammelte Tiefseefische
und ihre Augen. Marburg Sitz. Ber. Ges. Nat., 1902, 115-130.
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CLAPAREDE, D.
1875. Les annelides chetopodes du Golfe de Naples. Mem. Soe. Phys.
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CuARK, A. H.
1914. The correlation between the bathymetrical and geographical range
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1915. The correlation of phylogenetic specialization and bathymetrical dis-
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1915. The geographical divisions of the recent crinoid fauna. Jbid., 5, 7-11.
1915. The bathymetrical distribution of Arctic and Antaretie crinoids.
Ibid., 5, 76-82.
1915. On the temperature of the water below the 1,000-fathom line between
California and the Hawaiian Islands. Jbid., 6, 175-177.
COCKERELL, T. D. A.
1893. The entomology of the mid-alpine zone of Custer County, Colorado.
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Cuviger, L. C. F. D.
1834. Animal kingdom (London, Henderson), 3, 126-143, pls. 1-10.
DarsBoux, J. G.
1899. Recherches sur les aphroditiens. Trav. Inst. Zool. Univ. Montpellier
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EHLERS, E.
1864. Die Borstenwtrmer (Leipzig, Engelmann), xx + 748 pp., 24 pls.
1867. Reports on the results of dredging under the direction of L. F.
Pourtales, 1868-1870, and A. Agassiz in the Gulf of Mexico, 1877—
1879, in the U. S. Coast Survey Steamer ‘‘Blake.’’ Mem. Mus.
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1875. Beitrige zur Kenntniss der Vertikalverbreitung der Borstenwtirmer
im Meere. Zeit. wiss. Zool., 25, 1-102, pls. 1-4.
1912. Die bodensissigen Anneliden aus den Sammlungen der deutschen
Tiefsee-Expedition. Valdivia Tiefsee-Exped., 16, 1-167, pls. 1-23.
GRUBE, E.
1877. Anneliden Ausbeute, S. M. S. ‘‘Gazelle.’’ Monatsber. Akad. wiss.
Berlin, 54, 509-554.
Hotway, R. S.
1905. Cold water belt along the west coast of the United States. Univ.
Calif. Publ. Geol., 4, 263-286, pls. 31-37.
Horn, G. H.
1872. Coleoptera of Montana and portions of adjacent territories. Ann Rep.
U. S. Geol. Surv., 5, 382-396.
IzuKa, A.
1912. The errantiate Polychaetae of Japan. Jour. Coll. Sci. Tokyo, 30,
1-262, pls. 1-24.

232 University of Californa Publications in Zoology (Vou. 18

JOHNSON, H. P.
1897. A preliminary account of the marine annelids of the Pacific Coast
with descriptions of new species. Proc. Calif. Acad. Sei., (3) 1,
153-188, pls. 5-10.
1901. Polychaeta of the Puget Sound region. Proc. Soc. Nat. Hist. Boston,
29, 381-437, pls. 1-19.

IXINBERG, J. G. H.
1855. Nya slagten och arter of annelider. Ofv. K. Vet. Akad. Forhandl.,
Stockholm, 12, 381-388.
1865. Annulata nova. Ibid., 22, 167-179, 239-258.

KoForp, C. A.

1907. The faunal relations of the Dinoflagellata of the San Diego region.
Proc. 7th Inter. Zool. Congr., Boston, pp. 922-927.

1910. A revision of the genus Ceratocorys based on skeletal morphology.
Univ. Calif. Publ. Zool., 6, 177-187.

1911. Dinoflagellata of the San Diego region. The genus Gonyaulax, with
notes on its skeletal morphology and a discussion of its generic and
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LOEB, J.

1911. The role of salts in the preservation of life. Science, n.s., 34, 653—
665.

1915. The blindness of the cave fauna and the artificial production of blind
fish embryos by heterogeneous hybridization and by low tempera-
tures. Biol. Bull., 29, 50-67, 13 figs. in text.

McEwEn, G. F.

1912. The distribution of temperature along the coast of North America
deduced from Ekman’s theory of the upwelling of cold water from
the adjacent ocean depths. Inter. Rev, ges. Hydrob. Hydrog., 5,
243-286, 21 figs. in text.

1914. Peeuliarities of the Californian climate. Month. Weather Rev., 42,
14-33, 13 figs. in text.

1915. Oceanic circulation and temperature of the Pacific Coast, in Nature
and Science on the Pacifie Coast. (San Francisco, Elder), pp. 133—
139.

McIntosH, W. C. ;
1885. Report on the annelida polychaeta collected by H. M. S. ‘‘Challenger’’
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1900. A monograph of the British annelids. (London, Ray Society), 2,
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1912. Siidjapanische Anneliden. Denksch. k. Akad. Wiss., Wien, 72, 563—
580, pls. 1-3.
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MICHAEL, E. L.
1916. Dependence of marine biology upon hydrography and necessity of
quantitative biological research. Ibid., 15, i—xxiii.

1918 | Essenberg: Distribution of the Polynoidae 238

Moore, J. P.
1902. Description of some new Polynoidae with a list of other Polychaetae
from North Greenland waters. Proc. Acad. Nat. Sci., Phila., 54,
258-274, pls. 13-15.
1903. Polychaeta from the coastal slope of Japan and from Kamehatka
and Bering Sea. Ibid., 55, 401-490, pls. 23-27.
1905. New species of Polychaeta from the North Pacific chiefly from Alaska
waters. Ibid., 57, 525-554, pls. 34-36.
1908. Some polychaetous annelids of the northern coast of North America.
Ibid., 60, 321-364.
1909. Polychaetous annelids from Monterey Bay and San Diego, California.
Ibid., 61, 235-295, pls. 7-9.
1910. The polychaetous annelids dredged by the U. 8. 8. ‘‘Albatross’’ off
the coast of southern California. Ibid., 62, 328-402, pls. 28-33.
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234 University of Califorma Publications in Zoology [Vou. 18

STEUER, A.
1911. Leitfaden der Planktonkunde. (Leipzig, Teubner), 383 pp., 279 figs.
in text.
STOCKARD, C. R.
1909. The development of artificially produced cyclopean fish—‘‘ The
magnesium embryo.’’ Jour. Exp. Zool., 6, 285-337.
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1906. An investigation of evolution in chrysomelid beetles of the genus
Leptinotarsus. Publ. Carnegie Inst., 48, 1-314, pls. 3.
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1914. Polychaetous annelids of the Pacific Coast in the collection of the
Zoological Museum of the University of California. Univ. Calif.
Publ. Zool., 13, 175-238, 11-12, 7 figs. in text.
Watcortt, ©. D.
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1874. Anneliden an den Kiisten der Faeroeer. Zeit. wiss. Zool., 23, 346-349,
ple

po a a oo Fw p

[oe a a
CoN AAR YH ES

H. EXPLANATION OF PLATES

All figures drawn with camera lucida

PLATE 7

Tenth parapodium af Harmothoé hirsuta. X 15.
Dorsal cirrus of Harmothoé hirsuta. X 75.
Twentieth parapodium of Polynoé lordi. X 15.
Tip of upper neuropodial seta of Harmothoé hirsuta. X 75.
Tip of a long notopodial seta of the same. X 75.

Tip of a short notopodial seta of the same. X 75.

Tip of supra-acicular neuroseta of Polynoé lordi. X 160.
Tip of short notoseta of Lepidonotus squamatus. X 310.
Tip of a long notopodial seta of the same. X 310. |
Tip of ventral neuropodial seta of the same. X 310.

Tip of a ventral notopodial seta of the same. X 310.
Tip of blunt supra-acicular seta of Polynoé lordi. X 160.
Tip of neuroseta of Lepidasthenia gigas. X 160.

Tip of neuropodial seta of Polynoé fragilis. X 160.
Nineteenth parapodium of Polynoé fragilis. X 115.

Tip of notopodial seta of Polynoé fragilis. X 310.
Seventeenth parapodium of Lepidasthenia gigas. X 15.
Tip of upper neuroseta of the same. X 160.

Twelfth parapodium of Lepidonotus squamatus. X 20.

[236]

fESSENBERG]) PEATE ¥

18

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34,

PLATE 8

Fifth elytron of Harmothoé hirsuta.

Fringe of the same elytron. X 75.

x 15.
Small section of the same elytron showing the large tubercles. X 75.
22-24. Different kinds of tubercles of the same.

Tubercle of the same elytron, surface view.

X 75.

x 75.

Tenth elytron of Halosydna insignis (of commensal).

Tenth elytron of the same of free-living form.

Fringe of the same. X 75.
Tuberele of the same. X 70d.

Fifth elytron of Polynoé lordi. X 15.

Second elytron of Polynoé fragilis.

Tubercle of the first elytron of Lepidonotus squamatus.

Highly magnified portion of the second elytron of
squamatus showing the various types of tubercles and a few fringes.

x 15.

Fig. 35. First elytron of Lepidonotus squamatus.

[238]

X 16.

eliys

x 15.

x 310.

Lepidonotus
X 310.

UNMVmCALI PURE ZOOL, VOL. 18 [ESSENBERG] PLATE 8

ao igre he ‘
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eraw,

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. Description of Some New Species of .Polynoidae from the Coast of Cali-

3

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11. The Factors Controlling the Distribution of the Polynoidae of the Pacific

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‘ZOOLOGY

Vol. 18, No. 12, pp. 239-298, plates 9-11, 1 figure in text March 11, 1918

DIFFERENTIALS. IN BEHAVIOR OF THE TWO

“GENERATIONS OF SALPA DEMOCRATICA

_ RELATIVE TO THE TEMPERATURE
OF THE SEA

BY

ELLIS L. MICHAEL

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UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN
ZOOLOGY
Vol. 18, No. 12, pp. 239-298, plates 9-11, 1 figure in text March 11, 1918

DIFFERENTIALS IN BEHAVIOR OF THE TWO
GENERATIONS OF SALPA DEMOCRATICA
RELATIVE TO THE TEMPERATURE
OF THE SHA

BY
ELLIS L. MICHAEL

(Contribution from the Scripps Institution for Biological Research of the University of California)

CONTENTS

PAGE

JM ERO CINCO» cece: Face cece ee ee ae de eee 240
PeNvommy eoats UTD DIET ep Vga eS oe oe oo coc e ona Sunde cdgeaue Hench cose cucu duwebccuas pt eeee reeees emer e sees eae eee 241
lee DWeseripurommotpline yey Cle: <.255 ca. ck! cnc s. cde Le rs eee oe Ne 241
Zeorde data aud method of procedure -...-<..4.s ee ee ee 246

Do GIe He Cis CUSSTOME Ox: 15 as Onley ler cis trl OU GON seen a mee 250
Acie CiscusstONmOLeVertlealls Gist 11 Ut lO Ty seers eee eee ene 251

eee emi penaauie mam dls UieteLC@ (Cu Strato Ut LOA) oeesee sess =e eet ese ame es Ee 252
mene indonsenevedied: by data... i 2-.:---.:.scctee es oe eee 252

PP emer nOloci eal Mpc ation. 2.62462 <c.scecd. nee 256

3. Evidence of the existence of protruding chains ....................................... 258

Seen CaO Ser CO ar CO COMO TIO TY secs ce see eee eee 261
OriVe-Cxcymilmey tl OM" Ol Geavt ey foo e se ce ie Sect 2 ae rs een 262
ekelaiiony between Seasom amd tema ex ait Ur eee eee ene 262

2. Relation between position and temperature — 2222-222 kee et 265
Ost wal de SVASCOCILY: the Ot yar ts ate ae ROeIL ea 2 meee ean ante eee a aah eee 269

Dre eonye Of LOCOMOTION: «5235 sos oc eee ea ecg eet eee eee cade ee eee ean ck ee 271
ep Behbaviorvol Chains) :2.2-2-:.che a ee ee ee ee Ree eee ee ee eae Ae 271

2a Veduced peculiarities im) temperatume melaivors) seme ees tse see 274

Se AULU Ct ya Osea We pl aime OMG ONG @]) tremens teeter eee eee oe ss eee ee 281
eM ye ANd -COMMNISTIONS jee se ote eetee eee eee en eS eee en ee oes 1s eos 288

MeelatGenatune» Clue Ciec- si = erent see me tere aseas (SeDR ate ee sled coe tater Nae ese 291

240 University of California Publications in Zoology [ Vo. 18

INTRODUCTION

In working over the plankton collections made under the auspices
of the Scripps Institution certain peculiarities in the occurrence of
Salpa democratica, the smallest of the Salpae, led to an intensive study
of its distribution within the San Diego region. Although the study
is not yet complete, the relations revealed between fluctuations in sur-
face temperature and variations in surface distribution proved so strik-
ing and so significant, especially as regards the validity of the pre-
vailing plankton concept, as to make it advisable to publish at once
the results concerning this aspect of the problem.

The way in which the morphological complexities in the life cycle
are reflected in the distributional data makes it necessary to describe
in some detail the successive stages in this cycle. Moreover, these
morphological implications of the distributional data afford indis-
putable evidence of the fundamental interdependence of morphological
and ecological research; they demonstrate the necessity, if we are
ever rightly to interpret any biological phenomenon, of conducting
our investigations, not only in a rigorous and critical manner, but
also from the comprehensive natural history point of view so char-
acteristic of Darwin and his immediate followers—that point of view
which recognizes in all details of structure, function, behavior, and
variation the unifying fact of individual and species adaptation, and
which therefore holds all lines of research equally indispensable and
no fact of nature negligible. Again, the data uniquely demonstrate
that specificity in behavior is quite as far reaching as is specificity
in structure, the two generations of this species being quite as dis-
tinguishable from the way in which they are distributed as from the |
way in which they are constructed.

Lastly, the distributional data afford convincing evidence in sup-
port of the conclusion that 8. democratica, a typical plankton species,
controls to a significant extent its own distribution, and that it does
so, in part at least, by means of locomotion. This is in direct contra-
diction to the prevailing plankton concept, according to which plank-
ton organisms are, as Johnstone (1908, p. 148) truly says, ‘‘ particles
in the physical sense and behave as such.’’ Of course, no sane
biologist actually believes this, but plankton is nevertheless defined
in nearly every book dealing with such organisms, as ‘‘all floating
organisms which are passively carried along by currents’’ (Murray
and Hjort, 1912, p. 309). This matter is considered at some length
at the close of this paper.

1918 | Michacl: Behavior of Salpa democratica 241

The data involved in this investigation comprise all the collec-
tions made during the months of June and July prior to 1910 with
a surface net of 000XX mesh silk bolting cloth having an orifice 97.5
em. in diameter (Michael and McEwen, 1915). The reasons for
excluding later collections are first, that a net of very different
‘“‘eatching capacity’’ has been in use, and second, that the species
has been captured too seldom and in too small numbers to permit
satisfactory statistical treatment. The reason for excluding data
relative to other months than June and July is made evident in the
preliminary discussion of the seasonal distribution of the species.
Lastly, while the vertical distribution of the species is briefly con-
sidered preliminary to the main discussion, too few subsurface col-
lections were made at any one depth corresponding in time and place
with the surface collections, to justify burdening this paper with a
consideration of details of little aid in interpreting the facts revealed
by the surface data.

It is hoped that study of the distribution of this species may be
carried further in the near future. Does the species perform vertical
migrations? If so, to what depth does it migrate, and how is it
influenced by variations in light intensity, salinity, gas content, ete.?
These are questions as yet unanswered. But sufficient attention has
been given them to make it evident that a more complex statistical
method than the one here employed is needed. Such a method has
been devised, and is now being tested preparatory to publication.

I desire to express my obligation to Professor W. E. Ritter,
director of this institution; to Dr. F. B. Sumner, biologist; and to
Dr. G. F. McEwen, hydrographer, for suggestions and aid in the
preparation of this paper.

A. PRELIMINARY
1. DESCRIPTION OF THE LIFE CYCLE

Salpa democratica, like other species of the genus, is notable for
its two alternating generations. One, known as the ‘“‘solitary,’’
‘‘budding,’’ or incorrectly as the ‘‘asexual’’ generation (pl. 9, fig. 2)
produees offspring by budding, and the buds, when mature constitute
what is known as the ‘‘aggregate’’ or ‘‘sexual’’ generation (pl. 9,
fig. 3). Each individual of the aggregate generation then produces,
sexually, one of the solitary generation. So the cycle repeats itself.

242 University of California Publications in Zoology [ Vou. 18

Although there are important structural differences between indi-
viduals of the two generations, they are superficially so nearly alike
that the following description, borrowed mainly from Brooks (1893,
p. 4), relates as well to an individual of one generation as to one of
the other:

Each individual is transparent, ovate in form, and small, rarely
exceeding eight millimeters in length. Its body may be compared to
a barrel open at both ends so that water flows through it without
obstruction (text fig. A). The mouth (m) oceupies the anterior
end of the barrel, and the lips are infolded so as to act as valves per-
mitting the entrance of water but preventing its escape. At the

Fig. A (after Ritter). Semidiagrammatie representation of the solitary gen-
eration of Salpa democratica: (a) atrial aperture; (atr) atrium; (end) endo-
style; (g) gill; (m) mouth; (mn) nucleus or intestinal tract; (ph) pharynx;
(st) portion of stolon which has been converted into individuals of the aggre-
gate generation; (t) test or mantle cavity.

opposite end of the barrel the atrial aperture (a) affords an exit for
the water but, owing ‘to a few sphincter muscles, prevents it from
entering. Essentially, the chamber of the barrel is uninterrupted
from mouth to atrial aperture for, though divided by a rod-like gill
(g) into the pharynx (ph) and the atrium (atr), the gill is so nar-
row that it offers little obstruction to the water, and there is a large
free passage on all sides of it.

The body is partly encircled by six bands of muscles somewhat
lke barrel hoops crowded together on the upper surface midway
between the two ends of the barrel, and spread apart on the lower
surface. Contraction of these muscles empties the barrel, driving
the water out of the atrial aperture, and propels the salpa through the
water in the opposite direction. The body is encased in a thick, trans-
parent mantle or ‘‘test’’ (t) which, by its elasticity, antagonizes the
muscles and draws in a fresh supply of water. ‘‘The animal there-

1918 | Michael: Behavior of Salpa democratica 243

fore moves forward by jerks along a column of water which passes
through its body.”’

Within the body at the caudoventral extremity, hes a compact
intestinal tract called the nucleus (n). Closely associated with this
nucleus in the solitary salpa is an organ called the ‘‘proliferous
stolon’’ (st), which is a complicated tubular structure joined at its
proximal end to the body just anterior to the nucleus. Distally this
stolon segments, thereby giving rise to the aggregate salpae. Each
salpa remains attached to the preceding one in the form of a chain
and as the stolon continues to segment, the salpae are crowded and
pushed along a spiral path encircling the nucleus into the mantle
cavity (pl. 9, fig. 2). In fact all except the proximal end of the
stolon itself is coiled in the cavity of the test.

As the number of salpae in the chain increases each undergoes sev-
eral changes in position. As the origin and development of the chain
is so clearly described by Brooks (1893, p. 78) with reference to
Salpa pinnata and S. cylindrica, I can do no better than quote from
him and thereafter point out in what way S. democratica differs:

The first indication of the segmentation of the stolon is a series of ecto-
dermal folds which first appear at its sides, but soon extend up and down
and completely encircle it, and, pushing inwards, mark out the body-eavities
of the salpae, and also cut up the tubular structures inside the stolon into
segments.

The active agent in this process of segmentation is the growth of the
ectodermal folds, and the other structures are actually cut by these folds.
As a result of this process the nerve tube becomes cut up into a series of
ganglia, one for each salpa; the perithoracic tubes become cut up into a series
of perithoracie vesicles, two for each salpa; the genital string becomes cut
up into a series of eggs, one for each salpa,* inclosed in a follicle; and the
thickened endodermal epithelium at the sides of the endodermal tube becomes
cut up into a series of vertical pouches or pockets, two for each salpa, the
rudiments of the right half of the pharynx and of its left half.

The structures which I have enumerated form the rudiments of a single
salpa. At this stage each salpa is bilaterally symmetrical, and the plane of
symmetry is the same as that of the stolon, while its long axis is at right
angles to that of the stolon, which becomes converted into a single row of
salpae, so placed that the dorsal surfaces of all of them are toward the base
[proximal end] of the stolon, their ventral surfaces towards its tip [distal end],
their right and left sides on its right and left respectively, their oral [ anterior |
ends at its top or neural side, and their aboral [posterior] ends at its bottom or
genital side.

The single row of salpae becomes converted into a double row which con-
sists of a series of right-handed salpae and a series of left-handed ones, placed
with their dorsal surfaces out, their ventral surfaces toward the ventral sur-
faces of those in the opposite row, and the left sides of those on the right
and the right sides of those on the left towards the base of the stolon. In

———————————

*In S. democratica there are three eggs, but two disintegrate.

244 University of California Publications in Zoology [ Von. 18

order to illustrate these secondary changes in position let us represent the
series of salpae by a file of soldiers all facing the same way. Now imagine
that each alternate soldier moves to the right, and the others to the left, to
form two files still facing the same way. Now let them face about so that the
backs of those in one row are turned toward the backs of those in the other
row. They will now illustrate two rows of salpae.

To make the illustration more perfect suppose that, instead of stepping
into their new places, the soldiers grow and are pushed out by mutual pressure;
and suppose that their heads, growing fastest, form two rows while their feet
still form one row; and suppose furthermore that, as each soldier rotates, his
feet turn first, and that the twist runs slowly up his body to his head, which
turns last. We must also imagine that these various changes all go on together,
and that while they are taking place each soldier not only grows larger, but
develops from a simple germ to his complete structure.

In Salpa democratica the stolon undergoes more or less regular
periods of active segmentation and rest so that the aggregate salpae
are developed in sets or blocks, all individuals in a single block being
of approximately the same size and in the same stage of development.
Leuckart (1854, p. 67) found forty in one block and sixty-five in
another; while Seeliger (1886, p. 593) counted sixty-one in a single
block. As there are from three to four blocks present when the distal
end of the chain is ready to emerge from the mantle cavity to the
exterior, the stolon carries in the neighborhood of two hundred salpae
at one time. No evidence is at hand that the stolon ever exhausts
its capacity for producing them, and segmentation probably continues
until terminated by the death of the solitary salpa.

Again, in S. democratica, a later position is assumed by the salpae
such that those in one row of the chain alternate with those in the
other row, each salpa being connected by two processes from its body
wall with the one ahead of it, by two with the one behind it, and by
two to each of the two adjacent ones diagonally opposite it in the
other row. To quote again from Brooks (1893, p. 88) such a chain
‘“‘may be compared to two trains of ears on two parallel
tracks, placed so that the middle of each car on one track is opposite
the ends of the two cars on the other track, and each joined by two

of salpae

couplings to the ear in front of it on its own track, and in the same
way to the one behind it, and also to those diagonally in front of it
and behind it on the other track.’’ In this position ‘‘the long axis
of the salpae are at right angles to the long axis of the stolon, as if the
cars in the two trains were set on end.’’ Now imagine the ears in
each train to be pushed over until each one rests upon the one in
front of it, and at the same time imagine each ear to rotate so that
it becomes inclined outward at an angle of about forty-five degrees.

1918 | Michael: Behavior of Salpa democratica 245

The position of the cars will then illustrate the final positions assumed
by the salpae in a chain of S. democratica.

The embryo which is to become an individual of the solitary gen-
eration is carried and developed within the body of the aggregate
salpa. Before fertilization the egg is suspended by means of the
fertilizing duct, which opens into the cloaca, into one of the blood-
channels of the salpa. Quoting from Brooks (1893, p. 21): ‘‘The
spermatozoa, which are drawn into the pharynx ... with the sea
water, are swept past this opening by the contractions of the muscles
in swimming, and some of them enter it and one, penetrating to the
egg, fertilizes it.’’

Without going into detail, suffice it to say that the embryo at an
early stage pushes into the cloaca, carrying its wall before it, and thus
becomes inclosed in an epithelial capsule. Changes soon take place
by which this capsule becomes cast off and in its place, a placenta
forms which, communicating with the blood-channels of the salpa,
nourishes the growing embryo until birth. While the embryo projects
into the cloaca, it is not at first exposed to the water but is inclosed by
the epithelal capsule and after its disappearance, by an embryo sac
resembling somewhat the amnion of vertebrates. Later, but. still
while the embryo is very young, this sac is distended and finally
broken by the growing embryo, and from then until birth the embryo
is directly exposed to the water in the cloaca, being fastened to the
salpa only by the placenta and a narrow band of ectoderm which
connects the neck of the placenta to the walls of the cloaca.

As the embryo begins its growth shortly after the aggregate salpa
‘emerges from the mantle cavity of the solitary salpa, and as its
growth is rapid, a fully grown embryo is enormous in comparison to
the salpa which earries it (pl. 9, fig. 3). Leuckart (1854, p. 52)
says that, at birth the embryo of S. democratica is fully two-fifths the
size of the aggregate salpa. Before birth the stolon is completely
developed in the embryo and has begun to be converted into aggre-
gate salpae of the succeeding generation. After the embryo has made
its escape a testis develops in the aggregate salpae and they become
mature males.

In elosing this description attention must be called to several
inaccurate and misleading statements permeating the literature. One
frequently reads that the solitary form is asexual, that the aggregate
form is sexual (hermaphroditic), and that the developing embryo is
carried within the body of its mother. Such is not the case, for
Brooks has clearly demonstrated that the solitary form is, in the

246 University of California Publications in Zoology’ — | Vou. 18

strictest sense of the word, a female, while the salpa it produces by
budding is a male. Virtually, the mother salpa gives rise by budding
to her sons, and each son serves first as a depository for one of his
mother’s mature but unfertilized eggs, then as a living incubator
within which his mother’s daughter is housed and reared, and lastly
as a father. Such, in brief, is the curious sexual situation relative
to the life cycle of the salpae.

2. CruDE Data AND MeEtTHop oF PROCEDURE

All hydrographic data corresponding to hauls herein considered,
as well as description of the method of collecting, have been published
elsewhere (Michael, 1911; Michael and McEwen, 1915). Accordingly,
only those data directly concerned in the present inquiry are pre-
sented in table 1. But enough are included to permit anyone to check

the computations. For meaning of the term, section, see page 266.

TABLE 1

Data relative to June and July surface hauls of the years 1908 and 1909

Number of
Salpa democratica

Period Duration Temperature
Haul of in in Solitary Aggregate
number Date day* minutes Section Centigrade forms forms
1908

1417 June 12 12— 2 P.M. 20 43.0 1625 7 93
1418 June 12 10-12 a.m. 20 4310 16.4 11 81
1432 June 15 10-12 a.m. 20 42, 18.9 2 10
1436 June 16 8-10 A.M. 20 43.10 16.5 i 25
1438 June 16 10-12 A.M. 40 42, 18.5 0 0
1444 June 17 12— 2 P.M. 30 46,. 16.5 138 2860
1452 June 17 2— 4 P.M. 13 44,. 16.5 25 1542
1455 June 18 10-12 A.M. 3 45,5 16.5 23 212
1460 June 18 12— 2 P.M. 40 45.6 gl 4 23
1465 June 19 8-10 A.M. 40 46,. 17.8 310 1980
1471 June 19 10-12 a.m. 20 40,. 17.5 25 311
1478 June 23 4— 6 P.M. 20 42. 18.3 0 0
1505 June 26 12— 2 P.M. 25 42. 20.0 775 1047
1509 June 27 6— 8 A.M 17 40.1 18.6 0 0
1512 June 27 6— 8 A.M. 25 40. 18.9 0 0
1530 June 30 10-12 a.m. 20 50,5 15.5 3 55
1535 July 8 6— 8 A.M. 20 5216 18.9 0 0
1559 July 18 6— 8 A.M. 10 61, 16.5 0 0
1560 July 18 6— 8 A.M. 40 61, 16.5 60 +
1562 July 18 8-10 P.M. 60 61, 19.5 0 0
1579 July 22 6— 8 P.m. 20 40,5 20.8 0 0

_ _* In specifying the two-hour period it is assumed that the whole haul was made within the
limits given; actually it has, in many instances, overlapped on the preceding or succeeding
period. In such cases the period in which the greater amount of time was consumed is
entered in this table.

1918 | Michael: Behavior of Salpa democratica 247

TABLE 1—(Continwed)

Number of
Salpa democratica

Period Duration Temperature

Haul 0) in in Solitary Aggregate
number Date day* minutes Section Centigrade forms forms

1582 July 22 8-10 P.M. 25 40,5 20.5 0 0
1585 July 23 4— 6 A.M. 23 40,0 19.8 0 0
1588 July 23 4— 6 A.M. 25 40,6 19.7 0 0
1594 July 23 8-10 P.M. 22 40,15 20.5 0 0
1597 July 24 4— 6 A.M. 20 40,5 20.5 0 0
1600 July 24 4— 6 A.M. 20 4010 20.5 14 3

1909

1643 June 15 12— 2 P.M. 60 42.5 18.2 15 176
1650 June 16 4— 6 P.M. 45 42.0 18.6 6 0
1653 June 16 6— 8 P.M. 35 420 18.6 al 0
1657 June 16 6— 8 P.M. 35 42.0 18.4 0 0
1659 June 17 4— 6 P.M. 60 3940 18.4 0 0
1660 June 17 6— 8 P.M. 45 3940 18.4 0 0
1661 June 17 6— 8 P.M. 45 3940 18.4 0 0
1662 June 17 6— 8 P.M. 30 3950 18.4 0 0
1673 June 21 6— 8 P.M. 25 42,5 18.0 160 20
1680 June 21 6— 8 P.M. 35 4310 15.9 13 83
1686 June 22 4— 6 A.M. 60 4344 Ne) 0 0
1689 June 22 4— 6 A.M. 55 431, 17.9 0 0
1695 June 23 4— 6 A.M. 65 42.0 17.6 100 10
1698 June 23 6— 8 A.M. 40 42.15 17.2 132 8
1703 June 23 8-10 A.M. 115 42,5 ee 31 600
1712 June 24 4— 6 P.M. 70 42.5 17.5 46 4
1716 June 24 6— 8 P.M. 45 42.5 17.5 28 154
1719 June 24 6— 8 P.M. 68 42.0 17.2 20 219
1728 June 25 4— 6 P.M. 60 42.6 UW 7/ath 91 970
1734 June 25 6— 8 P.M. 37 42.5 A(eh 56 547
1738 June 25 8-10 P.M. 56 42.6 17.6 47 598
1747 June 28 6— 8 P.M. 36 420 19.0 13 387
1751 June 28 6— 8 P.M. 45 42.5 19.0 7 304
1754 June 28 8-10 F.M. 40 42,5 19.0 212 63
1759 June 29 4— 6 A.M. 20 42.) 18.6 500 40
1763 June 29 6— 8 A.M. 55 42.0 18.7 365 76
1767 June 30 4— 6 P.M. 25 49,, 19o 1000 73
1772 July 1 8-10 A.M. 28 9340 16.7 0 0
1779 July 1 10-12 A.M. 108 D240 20.4 2 8
1784 July 2 4— 6 A.M. 21 D240 18.7 28 1
1791 July 2 6- 8 A.M. 23 D210 16.6 0
1796 July 2 8-10 A.M. 30 46, 17.6 0 0
1800 July 2 12— 2 P.M. 51 42. 20.5 10 2
1804 July 2 4— 6 P.M. 27 41, 20.3 2 0
1810 July 2 6— 8 P.M. 50 41, 20.2 1500 63
1815 July 7 4— 6 A.M. 45 42.40 19.0 250 72
1826 July 7 6— 8 P.M. 60 40, 19.2 466 52
1836 July 7 8-10 P.M. 30 40, 19.4 165 20
1850 July 9 2— 4 A.M. 45 40.5 18.8 2 83
1854 July 9 4— 6 A.M. 55 40,5 18.8 3 21
1860 July 9 4— 6 A.M. 67 4010 18.6 0 21
1864 July 9 6— 8 P.M. 45 40,5 19.0 1 6

248 University of California Publications in Zoology [ Vor. 18

TABLE 1—(Continued)
Number of
Salpa denvocratica

Period Duration Temperature

Haul of in in Solitary Aggregate
number Date day* minutes Section Centigrade forms forms

1868 July 9 6— 8 P.M. 33 40,5 19.0 9 +
1872 July 9 6— 8 P.M. 35 40.6 18.8 0 12
1875 July 9 10-12 P.M. 170 40,5 19.0 0 89
1881 July 10 12— 2 a.m. 70 40,0 18.9 0 0
1883 July 10 12— 2 A.M. 213 40,; 19.2 53 1537
1888 July 10 4— 6 A.M. 45 40,; 19.1 22 220
1892 July 10 4— 6 A.M. 30 40,, 19.2 2 86

Several methods have been employed (Michael, 1911; Esterly,
1912) for determining the relative distribution of a marine species
under different conditions. First, the direct method was used of
comparing the abundance or average number of individuals obtained
per unit volume of water filtered (— amount filtered per hour of
towing). Second, as the species would in general be present in a
greater proportion of those hauls made under the conditions when the
species occurred in greatest numbers than of those hauls made under
the conditions when it occurred in smallest numbers, the haul fre-
quency, or percentage of hauls in which the species appeared under
one set of conditions, was compared with that under another set. It
is important that this be clearly visualized; perhaps an illustration
strictly analogous in principle although not in detail will make it
more intelligible. The President of the United States is elected not
by popular vote but by that of states. But, as a rule, the candidate
receiving the largest popular vote is elected. Suppose one wanted to
compare the Democratic preference of the nation during a period of
plenty with that during a period of famine. Assuming an equal popu-
lation in all states, could the investigator not proceed in two ways:
first, by comparing the average number of Democratic ballots east per
state under the two conditions (—the abundance method) ; and second,
by comparing the proportion of states that went Democratic under the
two conditions (=the frequency method)? If the first method indi-
cated a greater Democratic preference during the period of plenty, the
second method would, as a rule but not always, indicate the same thing.

Finally, Esterly (1912, p. 282) compared the time frequency of the
species under one set of conditions with that under another, or to
quote: ‘“‘the ratio between the time occupied by hauls in which the
If the average
time consumed per haul were the same for hauls made under all com-

2?

species was taken and the total time spent in hauling.

pared conditions, it is obvious that haul frequency and time frequency
would be identical. However, if ten hauls consuming ten hours were

1918 | Michael: Behavior of Salpa democratica 249

made in July, while ten hauls consuming five hours were made in
December, neither the haul nor the time frequency of the July hauls
would be comparable with that of the December hauls. For the
probability of capture by the ten hauls consuming ten hours, would
exceed that by the ten hauls consuming five hours. Therefore, it is
necessary to determine what the frequency would have been had the
ten December hauls consumed ten instead of five hours; otherwise both
haul and time frequency might be misleading.

Since haul frequency, by definition, is unrelated to the time con-
sumed in hauling, it can not be standardized with respect to time.
Time frequency, however, is amenable to such correction; and as
the method of standardization employed was developed by Dr. G. F.
McEwen of the Scripps Institution, I have asked him to give, in his
own language, the derivation of the formula:

Let F = time frequency,
f =standardized frequency,
a—average time per haul,
b = standard time per haul,
nat
f, = frequency corresponding to n units of time of duration a,
Pp: = probability of catching no animals in a haul of duration a,,

Then from the principle of compound probabilities of independent events:

f, -
“00 == 1p; time = a,,
cS yee 1—p, time = 2a
109=— Pa
a 1—p* time = 3a,
100 : 4
sae 1—p,;" time = na
0 fee ee
Let
b= kKa;
then
a= mka,
Therefore
f k
=e BOP RS a ee oR cee Ce at
100% 1 Pri ----- (1)
and
if) kK
as pies MORES Ny Nae tk ee, EIN 2 ee ieee a ROT 2 rer ree 2
100 1 Pi 1 ( )
From (1) and (2)
fi
jo = 1 ee 100 See eee ee ee ee eee ee ge ee ae oa ees ee er ae pao oe (3)
Bi
ee maa eae oe aaa oe eee nee eee R ER cee ne eee Aeneas ee (4)
Therefore, equating the logarithms of the second members of (3) and (4)
log (1 i) = > tog ei —) pots tee eee, Shots Standardization formula.

250 University of California Publications in Zoology | Vou. 18

Since the standardized frequency given by the above formula,
is that time frequency which would most probably have resulted had
every haul consumed the same amount of time (one hour), it is
equivalent to what the haul frequency would have been under the
same conditions. The latter is therefore of no avail and the methods
employed in this investigation are two: (1) the average number of
solitary forms and aggregate forms obtained per hour under the
various temperature conditions are compared; and (2) their standard-
ized frequencies under the same temperature conditions are compared.
By using these two methods, the first of which is affected by variability
in number of individuals collected while the latter is entirely inde-
pendent of such variability, a check on interpretation is maintained.

3. BriEF DISCUSSION OF SEASONAL DISTRIBUTION

Investigations concerning the distribution of the chaetognatha
(Michael, 1911, p. 139) revealed no apparent seasonal effect. Simi-
larly, no seasonal effect is apparent in the data discussed by Esterly
(1912) relative to the copepoda. In the ease of Salpa democratica,
however, the influence of season is pronounced. As revealed by the
following table, both generations of this species occur on the surface
mainly during the months of June and July, solitary forms being
restricted entirely to these months. No collections, however, were
made during the months of January, May, October, or December.

TABLE 2

Seasonal surface distribution of Salpa democratica during 1908-09

Number of animals

Average Solitary forms Aggregate forms
Hours of tempera- Average
Month Hauls_ hauling ture salinity Total Per hour Total Per hour
Feb. 5 6.5 13°6C 33.949 /5 5 0 0 6 1
Mar. 15 12.6 asst 33.64 0 0 0 0
Apr. 6 4.1 16.1 33.70 0 0 0 0
June 41 28.2 17.9 33.61 4,164 147 12,516 444
July? | 85) | 25.5 Telos ets ue i92) aoe 2,359 93
Aug. 15 6.5 TOG.) ) Wake 0 0 92 14
Sept. 6 Peo 18.5 33.88 0 0 14 Z
Nov. 5 2.6 17.9 33.85 0 0 0 0

In addition to the almost complete restriction of both generations
to the months of June and July, the table shows both to have been
more abundant during June than during July. Moreover, while the
aggregate forms were more abundant than the solitary forms during
June, the solitary forms were the more abundant during July. This
difference may have been consequent upon any or all of several influ-

1918 | Michael: Behavior of Salpa democratica 201

ences: (1) normal sequence in the life cycle; (2) the effect of higher
temperatures during July in increasing the abundance of solitary
forms; and (3) a similar effect of higher salinities during July. To
what extent and how each of these factors has operated in causing
the difference noted it is impossible to say, but it seems probable that
temperature has played an important part.. This is not only made
evident in the ensuing discussion but also by the fact that twenty-one
surface hauls made between August 9 and 23, 1911, in the vicinity
of San Diego when the temperature averaged 20°2C failed to catch a
single specimen of either generation, while on August 21, 1911, three
surface hauls made with the same net in the vicinity of Santa Rosa
Island when the temperature averaged 16°4C were all successful,
obtaining 115 solitary forms and 1409 aggregate forms.

In apparent contradiction to this fact, the table shows that aggre-
gate forms occurred to some extent during August although solitary
forms did not and judging from the high temperature average, this
is the reverse of what might have been expected. These facts indicate
the complexity of causes leading to the seasonal appearance and
disappearance of S. democratica.

When all the hauls in all depths are examined, June and July
still stand out as the months of maximum abundance, the number of
specimens obtained during other months being relatively few.

4. Brier DISCUSSION OF VERTICAL DISTRIBUTION

Considering horizontal closing net hauls from all depths, made
during the months of June and July, 1908 and 1909, a total of 6,889
solitary forms and 17,091 aggregate forms were obtained. Table 3
shows how they were vertically distributed.

TABLE 3
Vertical distribution of Salpa democratica during June and July, 1908 and 1909

Number of animals

Average Solitary forms Aggregate forms
Depth in Hours of tempera-
fathoms Hauls hauling ture Total Per hour Total Per hour
0 76 5a.t 18°36C 6,756 126 14,875 276
4-6 Wl Sal. iW este) 59 ily) 1,135 366
7-12 14 4.4 16.06 56 12 505 114
15-20 i) 3.2 12.92 13 4 297 93
25-35 14 4.4 10.97 3 a 253 57
40-75 14 4.1 9.73 2 1- 26 6
100-350 27 11.0 8.28 0 0 0 - 0

This table shows that solitary forms decrease in abundance as
the depth increases, disappearing entirely below 100 fathoms, while

252 University of California Publications in Zoology | Vor. 18
aggregate forms are most abundant between four and six fathoms,
decreasing from that depth until they also disappear below 100
fathoms. Here again, as in table 2, the maximum abundance of soli-
tary forms corresponds to a higher temperature than is the case with
aggregate forms. Is this correspondence merely consequent upon the
effects of random sampling, or does the temperature of the water play
an important and differential part in the distribution of the two

generations of this species?

B. TEMPERATURE AND SURFACE DISTRIBUTION

1. RELATIONS REVEALED BY DATA

The June and July data of the years 1908 and 1909 reveal a_
variation in surface temperatures taken simultaneously with surface
net hauls of five degrees Centigrade, or from 15°9C to 20°8C. When
these hauls are arranged in two groups according as the temperature
was 18°3C or less, or 18°4C or more, it is found (table 4) that an
average of 67 solitary forms per hour’and an average of 529 aggre-
gate forms per hour are associated with the lower temperatures, while
an average of 156 solitary forms and an average of 124 aggregate
forms are associated with the higher temperatures. In other words,
solitary forms were most abundant on the surface in the warmer
water, while aggregate forms were most abundant in the colder water.

TABLE 4

Relation between surface temperature and surface distribution of Salpa
democratica during the months of June and July,
1908 and 1909

Solitary forms Aggregate forms

Specimens Frequency Specimens Frequency
ee
Tempera- S x pat sf 5 5 36 a B 5
ture in n ee fag ° GS wus a S SC
2 Sa. saws ae Voor thas Unie ee eo gaa as
centigrade & 62 O92 5% BR a ao eNeny es Bon OB 7S
aa Te Gas a Ay = au fas a oY eH
15°9-18°3 30 20.0 16.2 1,346 67 81 92 16.2 10,575 529 81 92
18°4-20°8 46 34.7 204 5,410 156 59 69° 23.1 4,300 “124 67 77

Table 4 also shows that the frequency of both solitary forms and
aggregate forms was 92 when the temperature was 18°3C or less,

while that of solitary forms was 69 and that of aggregate forms 17, |

when the temperature was 18°4C or more. In other words both soli-

tary forms and aggregate forms were obtained most frequently in the
colder water. To sum up, table 4 shows:

1918 | Michael: Behavior of Salpa democratica 253

1. Solitary forms most abundant in the warmer water.

2. Solitary forms most frequent in the colder water.

3. Aggregate forms most abundant in the colder water.

4. Aggregate forms most frequent in the colder water.

5. Frequency of solitary forms very similar to that of aggregate
forms.

6. Abundance of solitary forms reversed to that of aggregate
forms.

With respect to aggregate forms these relations seem reasonable,
for the orders of their abundance and frequency are parallel as is to
be expected. Regarding solitary forms, however, the relations appear
to be meaningless. Do they not signify that the solitary forms are
found in greatest abundance in the places they frequent the least or,
to state it differently, that they are found most often under the con-
ditions when they occur in smallest numbers? Obviously, this is
precisely what is implied if the relations revealed by table 4 are not
due: (1) to systematic errors introduced by the method of collecting ;
(2) to the chance effect of random sampling; or (3) to what amounts
to the same thing, an insufficient number of hauls.

First, as to methods used in collecting. All collections were made
with surface nets of 000 mesh (Michael and McEwen, 1915, p. 201),
as nearly like one another as it is possible to construct them. Further-
more, the ‘‘ Agassiz’’ was allowed to drift during every haul, and the
error introduced by variation in volume of water filtered is far within
the differences in abundance noted in table 4. The ratio between the
mean variability (0.172 km. per hour) and average velocity of tow
(1.8 km. per hour) as determined from fifty hauls made with a cur-
rent meter attached below the net, is 0.01, while the mean variability
in number of organisms obtained per hour usually exceeds the average
number (Michael, 1916, p. xviii). It is unlikely, therefore, that lack
of standardization of nets or method of collecting could have been
responsible for the relations above revealed.

It may be urged, however, that the effect of random sampling, 1.e.,
an uneven distribution of hauls with respect to influences other than
temperature, might account for the above relations. This is partly
true; the hauls were unevenly distributed with respect to light, only
nine night hauls (6 p.m. to 6 A.M.) having been made in the colder
water, while thirty-three were made in the warmer water. The follow-
ing table, however, includes only night hauls and the same relations
persist.

254 University of California Publications in Zoology [ Vou. 18

TABLE 5

Reproduction of table 4 by excluding all except night hauls
(6 P.M. to 6 AM.)

Solitary forms Aggregate forms

Specimens Frequency Specimens Frequency
Tempera- S bp rte an y 8 ‘sé " H H
ture in ee ese ee = 5. th ages = = Peale hee
centigrade z 52 B98 <= ie EG Oe = 5 aq H
Mm He Has «8 & 8 & Dae oe Bi ei = 788
15°9-18°3 OF car oro 424 58 74 81 5.5 1,631 220 74 81
18°4—-20°8 33 26.0 14.5 3,248 125 56 63 184 3,084 118 71 79

This table shows that an average of 58 solitary forms per hour was
obtained in the colder water and an average of 125 per hour in the
warmer water, while an average of 220 aggregate forms per hour was
obtained in the colder water and an average of 118 in the warmer
water. Table 5 also shows that the frequeney of both generations was
81 in the colder water, while that of solitary forms was 63 and that
of aggregate forms 79 in the warmer water. Thus, table 5 corroborates
table 4 in every respect, solitary forms again appearing in greatest
abundanee and least frequency in the warmer water, while aggregate
forms appear in greatest abundance and greatest frequency in the
colder water.

Even when the data are arranged in every other practicable way
with respect to light, as in table 6, the same relations persist.

TABLE 6

Relation of surface distribution of Salpa democratica to temperature
with respect to different periods of the day

Solitary forms Aggregate forms
Specimens Frequency Specimens Frequency
Tempera- San OS a 5 BO wp 3 =
P ‘ Dn nw oS ua iS) S
ture in a) SBS HO.8 = zg 5 cS pears m= tt Ps z
centigrade & oe 598 = Fs & a Dee = = £ z
G He as oS iY - & Was a AY = ie

A—Ineluding only daylight hauls (6 A.M. to 6 P.M.)
15°9=18°3 21 9126 10:7 922-73". "85. 9b) 10.7 8,944" 710" So 96
18°4-20°8 13 8.7 59 2,162 249 68 82 4.7 1,216 140 54 68

B—-Including only intense light hauls (10 A.m to 2 P.M.)
ISS alisys 3} 8 fal aa. 226 55 100 100 41 3,811 930 100 100
18°4-20°8 5 39 3.4 789 202: 87 (2938) 3,104, 06%, (247 7 8749s
C—Ineluding only early morning hauls (6 A.M. to 10 A.M.)
3. 9 B58 4.2 B45 192 72186 | 42 e261) abk 7 2esG
—2058 § 4) 1-05 0:97)" 365 )asr 940 eit 0c 76,” §390) 4607s
D—Ineluding only evening hauls (6 P.M. to 10 P.M.)

15°9-18°%3 6 44 4.4 324 74 100 100 44 1,621 368 100 100
US24—2078) 18 Te5) (6:2) 2.374206 54) 70) 6:2 gyilit AS) tee (rAd)

1918 | Michael: Behavior of Salpa democratica 255

We have now considered the data in six different ways with similar
results. In table 4 data relative to all the June and July hauls are
considered, while in tables 5 and 6 night hauls, day hauls, mid-day
hauls, morning hauls, and evening hauls are separately considered ;
and in each ease the following relations are shown:

1. Solitary forms most abundant in the warmer water.

2. Solitary forms most frequent in the colder water.

3. Aggregate forms most abundant in the colder water.

4. Aggregate forms most frequent in the colder water.

It must be evident that such a variety in tabulation would introduce
contradictions were it not for a definite relation between fluctuations
in surface temperature (or some influence closely associated with it)
and the behavior of the two generations of this salpa. However, on
account of the apparently paradoxical relation between the abundance
and frequency of solitary forms, the probability that such a repeti-
tion of relations was due to chance, insufficient or madequate haul-
ing, or to anything other than an actual correspondence between tem-
perature and distribution has been calculated and found to be less
than 0.0007. The calculation is simple, as follows:

There are four possible ways in which the aggregate forms might have been
related to the colder water, namely:

1. Most abundant and most frequent.

2. Most abundant and least frequent.

3. Least abundant and most frequent.

4, Least abundant and least frequent.

Whichever of these combinations might result, it is obvious that the solitary
forms might have been related to the colder water in any one of the same four
ways. For each tabulation, therefore, there would be sixteen possible com-
binations of relations, any one of which would be equally likely to occur by
chance. Then, for any one of the sixteen possible combinations that appeared
in the first tabulation, there would remain sixteen possible combinations that
might appear in the second tabulation, whence the number of possible combina-
tions in two tables would be 16%. In three the number would be 16%, in four 16’,
and in six 16°. Hence, the probability that the same combination of relations
appearing in all six tabulations was due to chance is 4," or 1 > NGM, be
tables 4 and 5 as well as section A of table 6 be excluded on the ground that
they contain part of the data in the remaining tabulations, the probability would
be 1 + 16° or 1 + 1,536 which is less than 0.0007.

It may be claimed that this is an underestimate because of a natural associa-
tion between maximum abundance and maximum frequency. Suppose, then,
that the probability of maximum abundance and maximum frequency of the
aggregate forms occurring together is large—say P. Then, since there is an
equal chance of this combination being related to the colder or the warmer
water, the probability of its being related to the colder water in any one

tabulation would bes . From this it follows that the probability of minimum

256 University of California Publications in Zoology [ Vou. 18

abundance occurring with maximum frequency and also with the colder water

in any one tabulation (as is the. case with the solitary forms) would be a

Hence, the probability of maximum abundance and frequency of aggregate
forms being associated with minimum abundance and maximum frequency of

the solitary forms and with the colder water in any one tabluation is a =) or

9

9

“a -, and the probability of this happening three times in succession is CZ)

2y 3

a ) = Y¥,,*, and
since this is the value P assumes if abundance be independent of frequency,
it follows that the probability would be less than 14,° if a natural association
exists between maximum abundance and maximum frequency. Furthermore,
the magnitudes of the differences between maximum and minimum abundance
and between maximum and minimum frequency, as well as the number of hauls,
have not been considered, so that the probability 0.0007 must be regarded as
a large overestimate rather than an underestimate.

The value of this expression is largest when P= 1% or when(

It therefore follows that the odds in favor of the trustworthiness
of the relations shown by tables 4, 5, and 6 are sufficiently large (more
than 1,535 to 1) to justify the conclusion that temperature, or some
influence intimately associated with it, must play a prominent, albeit
a peculiar, part in the distribution of Salpa democratica.

2. A MorpHOLOGICAL IMPLICATION

What do the foregoing facts imply? Since solitary forms aecumu-
late on the surface in greatest numbers when the water is warm, while
aggregate forms accumulate in greatest numbers when the water 1s
eold, some definite relation must exist between them, compelling soli-
tary forms to be taken in cold water whenever aggregate forms are
captured, compelling aggregate forms to be taken in warm water
whenever solitary forms are captured, and preventing any of one
generation to be taken without some of the other. Were there no such
relation, | can conceive of no way in which the two generations could
be so nearly identical in frequency and at the same time reversed in
abundance.

Upon considering the life cycle, two possible relations are sug-
gested: (1) that individuals of the solitary generation are developed
until maturity within the body of those of the aggregate generation
(p. 245) ; and (2) that the aggregate salpae are budded off in the form
of a chain by the proliferating stolon of the solitary salpa (p. 243).
The first alternative might account for the capture of at least one
solitary form in cold water by each haul that captured a number of

1918 | Michael: Behavior of Salpa democratica 257

aggregate forms. For at least one individual of that generation might
be captured which contained an embryo sufficiently mature to be
dislodged during the processes of towing and washing the net and
condensing and handling the hauls, and so be counted as a solitary
form. If such were the ease, the frequeney of solitary forms would
be identical with that of aggregate forms in colder water. But, even
so, this could not account for the fact that those solitary forms cap-
tured in the warmer water were accompanied by aggregate forms, for
the embryo does not carry the adult, and aggregate forms are shown
to be most abundant in cold water, while solitary forms are most
abundant in warm water. The second alternative, however, completely
satisfies the conditions, providing the chain of aggregate salpae remains
attached to the solitary salpa after being protruded from its mantle
cavity into the water.

This will be rendered more intelligible, perhaps, if the problem
is stated in symbolical language. Let a solitary form be symbolized
by a cork, an aggregate form by an iron weight, warm water by the
surface of a pond, and cold water by the bottom of the pond. Flota-
tion is then analogous to accumulation in warm water, and sinking
to accumulation in cold water. Our problem may now be restated as
follows: Since corks float and iron weights sink, what is the relation
between them that necessitates taking some corks from the bottom of
the pond whenever a number of iron weights are taken therefrom,
and that necessitates taking some iron weights from the surface when-
ever a number of corks are taken therefrom?

Stated in this symbolical language, it is evident that the only
feasible answer is that at the time the corks and iron weights were
removed from the pond, they were tied together. Now, if by experi-
ment, we find that one cork will barely float six weights, corks with
more than this number of weights attached would sink, while those
with less attached would float. Moreover, if those corks with more
than six weights attached wsuwally outnumbered those with less
attached, while occasionally those with less attached far outnumbered
those with more attached, then both corks and weights would be so
distributed with respect to surface and bottom that, while corks in
the long run would be obtained in greater numbers from the surface
than from the bottom, at least one would be present in a larger per-
centage of bottom than of surface hauls. in other words corks would
be most abundant and least frequent on the surface, while iron weights
would be most abundant and most frequent on the bottom.

258 University of California Publications in Zoology [| Vou. 18

This hypothetical distribution of corks and iron weights exactly
parallels the distribution of the individuals of the two generations of
Salpa democratica as demonstrated by tables 4 to 6. The conclusion,
therefore, seems unescapable that each aggregate salpa, after being
pushed to the exterior of the solitary salpa, remains attached to its
predecessor and that this chain of salpae also remains attached to the
solitary salpa as in other species of the genus.

3. EVIDENCE OF THE EXISTENCE OF PROTRUDING CHAINS

The conclusion being reached that protruding chains of Salpa
democratica are of normal occurrence, it is well before assuming its
truth, to consider whatever other evidence there may be. To this end
the literature has been searched without finding a single unequivocable
statement. Brooks (1893, pl. xii) has published a drawing of what
he calls: ‘‘part of a fully grown chain of Salpa democratica.’’ It
consists of six salpae attached together as described on page 244, but
the magnification is not given and, while it is probable from the con-
dition of the test that Brooks had a portion of a protruded chain
before him, it is possible that by ‘‘fully grown chain’’ he means the
final positions assumed by the salpae in the terminal portion of the
stolon. Again Herdman (1889, p. 58), after refering to a cut of
the posterior end of the solitary form of S. democratica, says: ‘‘ After
the solitary Salpa has become fully developed, the chain produced
by the stolon is set free in sections, each section being composed of a
number of aggregated Salpae at about the same stage of develop-
ment.’’ This statement sounds definite and explicit, but it is not clear
that it refers to S. democratica in the first place nor to the freeing
of the salpae from the mantle cavity of the solitary form in the second
place: by ‘‘set free in sections’’? Herdman may refer to the periodic
manner in which the stolon segments (see page 244).

But, Herdman’s statement is corroborated by that of Agassiz
(1866, p. 20) who, in describing S. cabotti—probably a large variety
of S. democratica—says: ‘‘The young Salpae are not uniformly
developed in proportion to their distance from the base of the tube
[stolon]. Sections of the tube are equally advanced and we find
generally, three such portions unequally developed. . .. The base of
the geminiferous tube is simply slightly corrugated, next comes a
section in which we find two rows of slight elevations, and finally the
most advanced part of the chain where the rudimentary Salpae are

1918] Michael: Behavior of Salpa democratica 259

more or less advanced and resemble in every respect, long before it
becomes detached, the chains which are found floating about. These
sections are thus liberated in turn, new ones continually forming at
the base of the geminiferous tube during the budding season... .
These chains escape through an opening formed at the proper time
through the tunic [test], near the nucleus on the ventral side, which
shows afterwards no trace of the passage of the small chain.’’ Agassiz
repeatedly refers to these liberated chains so that, if S. cabotti is in
reality only a variety of S. democratica, it is evident: (1) that the
chain of aggregate forms remains intact after, as well as before, escap-
ing from the mantle cavity of the solitary form; and (2) that the chain
is liberated in blocks of from forty to sixty individuals. Obviously,
this means that protruding chains must exist during the period of
liberation, but what length of time this involves is not indicated.

Aside from these three instances I have failed to find a single
statement applicable in any way to the question as to whether or not
the salpae remain attached in the form of a protruding chain. In
fact the attitude of those familiar with the group seems to be either
that such chains may be assumed to exist on general principles, or
that they do not exist in this species.

But negative evidence is never conclusive. Following up the
implications of tables 4 to 6, examination of the crude data (table 1)
shows that every haul that captured more than six solitary forms,
and all but three capturing less than six, also captured aggregate
forms. The three that failed (hauls 1650, 1653, and 1804) were all
made in water exceeding 18°9C. Moreover, as aggregate forms accu-
mulate in cold, and solitary forms in warm surface water, a con-
siderable number of hauls made in the colder water ought to have
captured aggregate forms, but no solitary forms, if protruding chains
or salpae containing mature embryoes were not frequently encount-
ered; but not a single such haul was made. Again, hauls made in the
warmer water ought frequently to have captured solitary forms, with-
out aggregate forms, if protruding chains were not generally encount-
ered ; but only three such hauls were made.

Further examination of the crude data reveals three more hauls
(1860, 1872, and 1875) made in water exceeding 18°9C which eap-
tured 21, 12, and 89 aggregate forms respectively, but no solitary
forms. Why? In answering this question it must be recognized that
during the processes of washing the net and of condensing, separating,
and examining the hauls a few specimens are nearly always lost. Con-

260 University of California Publications in Zoology [ Vou. 18

sequently, in hauls encountering only a very few protruding chains
the chance of losing the single solitary salpa of each chain would be
much greater than that of losing all the aggregate salpae. This, I
believe, is why no solitary forms were found in these three hauls.
Moreover, in four others (1432, 1779, 1854, and 1864) individuals of
the aggregate generation alone were recognized at first, but on reéx-
amination mature solitary forms were fownd, which makes the above
explanation more plausible. The crude data also show that out of
thirty-six hauls made in water below 18°6C, each of twenty-five con-
tained both solitary forms and aggregate forms, while each of the
remaining eleven failed to obtain a single individual of either genera-
tion. This seems explicable only on the assumption that protruding
chains were encountered in nearly if not all successful hauls.

It is well known that chains of even such large species as Salpa
fusiformis and S. zonaria are obtained entirely intact only with the
greatest difficulty. Says Herdman (1889, p. 59): ‘‘Out of the
enormous number of aggregated Salpae collected during the Challenger
expedition, none were adhering together when they reached my hands.
In all cases the chains . . . had become broken up into their con-
stituent Salpae.’’ Although this has not been the result of collections
made under the auspices of the Scripps Institution, chains of no
species have been obtained entirely intact except when collecting with
extreme care with a dip-net. Would ‘it be surprising, then, if the
pressure and swirl of the water in a tow-net completely breaks up —
whatever chains of the smallest and most delicate species, S. demo-
cratica, may be encountered ?

Granting this to be the explanation why protruding chains of
this species have never been described, it follows that the effect of the
swirling water in causing breakage would be less pronounced the
shorter the duration of the haul. Working over the collections from
this point of view, it was noticed that, while all the hauls herein con-
sidered consumed upwards of twenty minutes, a few thirteen-minute
hauls had been made in the vicinity of Santa Rosa Island during
August, 1911. Furthermore, while no portion of a chain was found
in any of the hauls entered in table 1, several fragments were dis-
covered in one of the above mentioned thirteen-minute hauls (2766).
In three instances two aggregate forms were found attached together ;
in another, three larger ones were attached; and in still another, five
were attached together so as to form a double chain as illustrated in
plate 9, figure 1. There can, therefore, be no doubt that, as Agassiz

1918 | Michael: Behavior of Salpa democratica 261

(1866) has said, each aggregate salpa remains attached to its pre-
decessor after as well as before being pushed out of the mantle cavity
of the solitary salpa into the water. Does it seem unlikely, then, that
the chain also remains attached to its progenitor ?

4. IMPLICATIONS REGARDING LOCOMOTION

If, as claimed on page 260, the general occurrence of protruding
chains is the only feasible explanation of all the temperature relations,
then some form of locomotion of the individuals of the two generations
is implied. For, to return to the corks and iron weights, the only
hkely manner in which corks could be most abundant and least fre-
quent on the surface, while the attached iron weights were most
abundant and most frequent on the bottom is, as stated on page 257,
for corks with less than a given number (six) of attached weights to
float and for those with more attached to sink. That is, the presence
of weights on the surface would be consequent upon the buoyancy of
the attached cork, and the presence of corks on*the bottom upon the
sinking propensity of the attached weights.

Translating back into Salpa terminology, the inference seems clear
that protruding chains of less than a given but unknown number of
aggregate salpae—short chains—are prevented from leaving an area
of warm surface water by virtue of the activity of the attached soli-
_ tary form, while with chains consisting of more than this number—
long chains—the solitary form is prevented from escaping out of an
area of cold surface water by virtue of the combined activity of the
attached aggregate salpae. I do not mean to stipulate that aggregate
forms are negatively thermotactic and solitary forms positively ther-
motactic, nor that long chains move horizontally out of warm into
cold areas of surface water, while short chains move horizontally
out of cold into warm areas of surface water. This may or may not
be the true explanation, but it seems unlikely. Further, it is not
stipulated that aggregate forms are negatively geotactic and solitary
forms positively geotactic in cold surface water, while the responses
are reversed in warm surface water. This, again, may or may not be
the true explanation; the data are inconclusive. Lastly, it is not
stipulated that an internal control by aggregate forms and solitary
forms over their own specific gravities leads to an accumulation of
short chains in warm surface water and long chains in cold surface
water; nor is it stipulated that some form of metabolic rhythm is

262 University of Californa Publications in. Zoology [| Vou. 18

involved. Onee, again, either of these may or may not be the true
explanation, but neither seems likely. What the uneseapable implica-
tions of the data are, may be listed as follows:

1. Short chains accumulate in warm surface water and long chains
in cold surface water.

2. Since the only difference between short and long chains con-
sists In the number and size of the attached salpae, a differential in the
distribution of the two generations must be due to a differential in
behavior of short and long chains, which obviously implies a differen-
tial in behavior of the solitary form and aggregate forms constituting
the chains.

3. The only type of behavior consistent with all the facts is some
form of locomotion.

However, these are implications—not facts—and it is necessary to
gain some idea of their reliability by reéxamining the data.

Cr REEXAMINATION OF THE DATA
1. RELATION BETWEEN SEASON AND TEMPERATURE

It has been suggested that the difference between short and long
chains may actually not have been restricted to the number and size
of the attached salpae. This, it is said, would be true only if all
possibility of seasonal influence were eliminated. In other words,
it is argued that, owing to an intimate association between increasing
temperature and advancing season, even within the limits of June and
July, 1908 and 1909, the relation between temperature and abundance
of the two generations may have been consequent upon an increased
production of solitary forms and an increased death rate of aggregate
forms.

On first thought this seems reasonable, but careful consideration
proves it untenable. For each individual of the aggregate generation
can give birth to only one solitary form, so that an increased produc-
tion of the latter requires an increased number of the former. Further-
more, as stated on page 245, the embryo is carried and developed within
the body of the aggregate form and is not set free until after it has
reached maturity and its stolon has begun to be converted into the
salpae of the succeeding aggregate generation. Consequently, all
hauls obtaining an excess of solitary forms over aggregate forms would,

1918 | Michael: Behavior of Salpa democratica 263

according to this hypothesis, have to be restricted to that time interval
between, the death of many of the embryo-bearing salpae and pro-
trusion from the mantle cavity of thé solitary forms of the first salpae
of the next generation—a time interval which is brief if it occurs at
all. If this were not the case, either no significant temperature rela-
tions would have appeared in the data, or aggregate forms as well as
solitary forms would have been most abundant in the warmer water,
both of which are contrary to fact. Moreover, the hypothesis requires
the death of a large number of aggregate forms prior to their maturity,
for, as stated on page 245, the testis does not develop until after
the embryo has matured and made its escape. Does this seem reason-
able?

But to speculate gains naught. The hypothesis is therefore sub-
jected to an empirical test. Table 7 gives the distribution of hauls
involved in tables 4, 5, and 6 with respect to each of the four months
concerned: June and July, 1908, and June and July, 1909.

TABLE 7

Distribution of hauls with respect to season

Temperature June, 1908 June, 1909 July, 1908 July, 1909
in ary ee Sas ee WS =e
centigrade Hauls Mean date Hauls Mean date Hauls Mean date Hauls a
ate
Section A—Hauls involved in table 4
15°9-18°3 iil 18 14 23 2 19 3 5)
18°4-20°8 5 20 13 22 9 21 19 ii
Section B—Hauls involved in table 5
15°9-18°3 0 ie 9 23 0 a 0 see
18°4-20°8 0 Jets 9 23 8 22 16 8
Section C—Hauls involved in table 6A
15°9-18°3 11 18 5 22 2 19 i 5
18°4-20°8 5 20 4 23 1 8 > 2
Section D—Hauls involved in table 6B
15°9-18°3 fal 18 il 15 0 sat oa
18°4-20°8 3 19 0 ~eet 0 bee ill 2
Section E—Hauls involved in table 6C
15°9-18°3 2 i7/ 2 23 2 18 3 5
18°4-20°8 2 PAL i 29 1 8

Section F—Hauls involved in table 6D

15°9-1873 0 cee 6 24 Q A 0 aa
18°4—20°8 0 = 8 21 4 21 6 7

264 University of California Publications in Zoology [ Von. 18

From these data it is difficult to understand how any seasonal
effect could have been responsible for the temperature relations
revealed by tables 4 to 6. In the first place section A shows that, while
six more hauls were made during June, 1908, in the colder than in
the warmer water, the five made in the warmer water were, as indi-
cated by the mean date, made somewhat later in the month than were
the other eleven. According to the hypothesis under consideration
this might lead to an excess of solitary forms and a deficiency of
ageregate forms in the warmer water. But the differentials revealed
by table 4 could not have been due to the influence of this month
because the same differentials are shown by table 5, and section B of
the above table shows that none of the hauls involved in table 5 were
made during June, 1908. Likewise, it is shown by section D that
none of the hauls involved in table 6B were made during July, 1908;
yet the same differentials are revealed by it as by table 4, which
obviously means that the differentials could not have been due to the
way in which the hauls were distributed throughout July, 1908.
Similarly with respect to July, 1909: section E of the above table
shows that no hauls were made in the warmer water between 6 A.M.
and 10 a.m. (table 6C), while section F shows that none were made in
the colder water between 6 p.m. and 10 p.m. (table 6D). Yet the
differentials revealed by tables 6C and 6D, to which these data relate,
are identical.

It is clear, then, that the hypothesis under consideration must
justify itself, if at all, on the way in which hauls were distributed
during June, 1909. But all five sections of table 8 show: (1) an almost
exact equality between number of hauls made in the colder water
and in the warmer water; (2) an almost identical mean date relative
to hauls made in warm and cold water; and (3) that the slight differ-
ences in mean date that do exist are erratic with respect to the tem-
perature of the water; two instances (section A, and F) indicating
that the hauls made in the colder water were also made somewhat
later in the month than were those made in the warmer water, while
two instances (sections C and E) indicate that the reverse was
true.

To demonstrate completely the inadequacy of this hypothesis, table
4 is reconstructed by eliminating therefrom all hauls except those
made during June, 1909. The results are given in the following
table:

1918 | Michael: Behavior of Salpa democratica 265

TABLE 8

Reconstruction of table 4 by eliminating all hauls except those made
during June, 1909

Solitary forms Aggregate forms
a
Specimens Frequency Specimens Frequency
\ aa
ue oH Ser) u Hes H H
Tempera S on Sw : 5 Sb 2 FI
ture in a: ze £o5 es S Sy ep ne = a Soe pe
centigrade S ee veus S 3 = B 698 S) Ey = 5
q Go as = Ay H Ff ae a a a A
15°9-18°3 el” alej2) lls 739 56 86 88 11:3 3/389 257 86 88
18°4-20°8 AL 3} 8.6 5.0 2,104 245 58 80 3.7 943 110 438 63

Table 8 not only shows the same relation as does table 4, but
demonstrates that elimination of the seasonal effects due to the other
three months intensifies the difference between the abundance of soli-
tary forms in the colder water and their abundance in the warmer
water. In the colder water their abundance is reduced from 67 per
hour (table 4) to 56 per hour (table 8), while their abundance in the
warmer water is increased from 160 per hour (table 4) to 245 per
hour (table 8). Therefore, although advancing season and increasing
temperature were associated, the salpae were so distributed during
the months to which these data relate as to make it highly improbable,
if not impossible, for the relations revealed by tables 4 to 6 to have been
consequent upon the seasonal succession of the two generations.

2. RELATION BETWEEN POSITION AND TEMPERATURE

Another hypothesis has been raised. It is argued on the basis of
certain evidence relating particularly to aphids and rotifers that
high temperatures might favor production of solitary forms. Although
some of the more recent investigations (Whitney, 1907; Shull, 1911)
make such an effect of temperature doubtful, other causative factors,
such as substances in solution, may be so associated with temperature
as to lead to a greater production of solitary forms at high tempera-
tures. It is well, therefore, to consider this hypothesis.

According to it the differentials established by tables 4 to 6 are
consequent not upon locomotion of solitary forms and aggregate forms,
nor upon their seasonal succession, but upon a stratification of sur-
face water into areas of high and low temperature, in the former of
which solitary forms predominate because of their greater production,
while aggregate forms predominate in the latter because of their
greater death rate in the warm areas. As in the case of seasonal suc-

266 University of Californa Publications in Zoology [ Vou. 18

cession, it is difficult to see how solitary forms could by this means
predominate in the warm areas without also involving a predominance
of aggregate forms in the same areas. For, as stated on page 245, each
individual of the aggregate generation can give birth to but a single
solitary form and then not until the stolon of the latter has begun
to be converted into salpae of the next generation. This makes it neces-
sary, aS in the ease just considered, for all hauls obtaining an excess
of solitary forms over aggregate forms to have been made during that
brief and improbable time interval in the life cyele between the pre-
mature death of many of the embryo-bearing salpae and protrusion
of the first salpae of the next generation from the mantle cavity of
the solitary form.

But, assuming the hauls to have been made in this improbable if
not impossible manner, the verity of the hypothesis hinges upon
whether or not stratified areas of warm and cold surface water per-
sisted for a sufficient length of time. In other words, were the major-
ity of warm water hauls made at one set of positions and the majority
of cold water hauls at another set? If so the above hypothesis might
be true; if not it is obviously inadequate.

To answer this question the following list is supplied, which gives
the distribution of hauls involved in table 4 with respect to position,
the unit of position being a rectangular area or section of five miles (or
more accurately five minutes), on a side. In designating the section,
the number denotes its distance in five-minute units west of 114°W,
while the subscript denotes its distance in five minute units north of
32°N. For further explanation see Michael and MeEwen (1915,
p. 46; 1916, p. 217) and McEwen (1916, pls. 1-8).

List SHOWING DISTRIBUTION OF HAULS INVOLVED IN TABLE 4 BY SECTIONS

Number of hauls in Number of hauls in
a (2
Cold Warm Cold Warm
water water water water
Section 15°9-18°3C 18°4—-20°8C Section 15°9-18°3C 18°4-20°8C
39,0 0 4 4515 1 0
40,5 0 15 45, 1 0
40,, 0 7 46, 1 0
40,. 1 0 46,5 2 0
41, 0 2 49,, 0 1
42, 1 3 501, 1 0
42, i) 1 eh. 1 2
42. 11 9 5215 0 1
4310 4 0 53,0 1 1
43,, 2 0 61, 2 1
44, 1 0

1918 | Michael: Behavior of Salpa democratica 267

This list shows that as the distance from the coast increased the
number of hauls made in the cold water relative to those made in warm
water, as a rule, also increased. According to the hypothesis under
consideration, this might lead to an excess of aggregate forms in the
colder water and an exeess of solitary forms in the warm water and so
account for the differentials.

But, as shown by table 9, the excess of warm water hauls in sections
39,5, 40,5, 41s, 425, 42,, and 49,, together with the excess of cold water
hauls in sections 40,,, 48,,, 44,., 45,,, 45,., and 50,, can not account
for the differentials in question, for the reason that the differentials
are revealed by table 6C as well as by table 4, and none of the hauls
involved in table 6C were made in these sections. Similarly, the excess
of warm water hauls in sections 40,, and 52,, together with the excess
of cold water hauls in 46,, 53,, and 61. can not account for the differ-
entials because none of the hauls involved in table 6B were made in

TABLE 9

Distribution of hauls involved in tables 5 and 6 with respect
to position

Table 5 Table 6A Table 6B Table 6C Table 6D

|

Warm water

Posooooeo eee Se SeoNAseoeor Oo WF WY 18°4 99°80

Cold water

Scoooeoeoo eee eeorRNST SSS OS SP SO 15°9-18°3C

Warm water

Warm water
SorocoooooocoeooeorFe SF SSW OS © 18°4-20°8C

SSSHSOSSOSOSCOSO OOH NSOOOS SC jg04 o00g0

Cold water

SS ee I AOC eae Y

Cold water

ROE tie SOR Oe Ae OR ONS SSW OO) OS S32 SO (5c O= 18996

Warm water

SS TS SS SS IS aC NOX)

Cold water

Warm water
SS SS TS eo er SS FOO IIESIE!

HOSOH OSC OS OSC OO ONO SCHON w 1Q04 99°C

Cold water

i

[w)

L--}
SocooONHaAcCSoOoOSoOSCSCOS :
Soococooo THO =1se3C

Section

(sy)
i)
iC

He
(=)

5
Nek

40,,

268 University of California Publications in Zoology [ Vou. 18

these sections, and this table as well as table 4 reveals the differentials.
Again the excess of cold water hauls in section 46,, can not have been
responsible, for none of the hauls involved in table 5 were made in
this section. Finally, the excess of warm water hauls in section 52,,
can not have eaused the differentials, because none of the hauls
involved in table 6D were made in this section.

All the sections except 42,, and 43,, are thus eliminated from
further consideration. Relative to the latter, all the hauls were made
in the colder water. According to the hypothesis in question this
might account for the excess of aggregate forms in the colder water.
Still, it obviously can not account for the excess of solitary forms in
the warmer water. But, neither ean the distribution of hauls in sec-
tion 42,, account for it, for not only were more cold than warm water
hauls made in this section, but table 9 shows that none of the warm
water hauls involved in table 6B were made in it. Furthermore, every
haul made in this section was made within 0/3 of 32° 52’N and all
except one (1657), which failed to catch a single individual of either
generation, within 0°4 of 117° 30’W. Finally, every haul save one
(1815, made on July 7, 1909) was made between June 15 and June 29,
1909. This obviously means that, even if stratified areas of warm and
cold water did exist within the required limits of approximately 0.64
square miles—a highly improbable occurrence—the time elapsed was
insufficient to enable the excess of solitary forms and deficiency of
aggregate forms in the warmer water to have arisen in consequence
of an increased production of the former and death of the latter. It
follows, then, that if table 4 be reconstructed by eliminating all hauls
except those made in section 42,,, this stratification hypothesis will
be put to its final test. Table 10 shows the results of such reconstruce-
tion.

TABLE 10

Reconstruction of table 4 by eliminating all hauls except those
made in section 42,,

Solitary forms Aggregate forms
ese
Specimens Frequency Specimens Frequency
Tempera- Sica ince eH P ‘36 a SI H
ture in a) Bley Ge = = a =| Oo. = é © Z
centigrade 89 52 532 ¢ Ba. Si BS See Be Bales
as] ewiaaieet Pacp Svc bye oe Ea Ap eee Oo ~ Sod Gay
15°9-18°3 LON ONT 726 68) 1007 100) 1103732306) 309) 00) 100
18°4—-20°8 9 5.9 do liso 4 3229 90 98 4.0 942 160 68 80

1913] Michael: Behavior of Salpa democratica 269

According to the stratification hypothesis this table ought to show
an approximate equality between the abundance of solitary forms in
the warmer water and their abundance in the colder water, and also
between the abundance of aggregate forms in the warmer water and
their abundance in the colder water. This is obviously not the ease.
The relations shown by table 10 are essentially the same as those shown
by table 4, solitary forms again appearing as most abundant and least
frequent in the warmer water, while aggregate forms appear as most
abundant and most frequent in the colder water. Not only is this true,
but the difference in abundance of the solitary forms in the warmer
and that in the colder water has been increased from 93 in table 4
to 161 in table 10. Therefore, although the temperature did decrease
with increasing distance from the coast, the two generations were so
distributed with respect to position as to make it quite impossible for
the differentials revealed by tables 4 to 6 to have been due to stratified
areas of warm and cold surface water, or what amounts to the same
thing, to differences in position.

3. OstwaLp’s Viscocrry THEORY

The inadequacy of this theory to explain vertical migrations has
been pointed out before (Michael, 1916, p. xiv). It is not my pur-
pose, therefore, to discuss the theory in detail. But, as someone is
sure to claim that variation in viscocity of the water induced by
variations in temperature is responsible for the differentials observed
in the surface distribution of Salpa democratica, it 1s necessary to
forestall this claim. The matter will be considered on the basis of
three alternative assumptions: (a) that solitary forms or short chains
have the same specific gravity as aggregate forms or long chains; (b)
that solitary forms or short. chains are heavier than aggregate forms
or long chains; and (c) that aggregate forms or long chains are the
heavier.

It needs no argument to demonstrate that if, the first case (a) were
true, differentials in distribution of the two generations would be
impossible if due solely to viscocity effects. For if owing to an increase
in temperature, the viscocity decreases sufficiently to cause the indi-
viduals of one generation to sink, those of the other generation, being
of the same specific gravity, must also sink.

In the second case (b), a decrease in viscocity might cause solitary
forms or short chains to sink while aggregate forms or long chains

270 University of California Publications in Zoology [ Vor. 18

remained on the surface. This would, however, require a lower
viscocity in cold than in warm surface water, for otherwise aggregate
forms would be most abundant in warm surface water and least
abundant in cold surface water, which is contrary to fact. But even
so, it would be physically impossible for solitary forms or short chains
to remain in maximum numbers on the surface when aggregate forms
or long chains were present in minimum numbers. For, the former,
being heavier than the latter, must sink if the latter do.

The third assumption (c) is, perhaps, the most probable, because
since many individuals of the aggregate generation contain an embryo
of the solitary generation, it may well be that their specific gravity
exceeds that of the solitary forms and, for the same reason, the specific
gravity of long chains may actually exceed that of short chains. Under
these conditions a decrease in viscocity induced by an increase in
temperature might permit the sinking of aggregate forms or long
chains while solitary forms or short chains remained on the surface.
This might explain why aggregate forms were most abundant and most
frequent in the colder surface water and least abundant and least
frequent in the warmer surface water. But, as in case (b), solitary
forms could not be more abundant in warm than in cold surface water,
for cold water, being denser, anything heavy enough to sink in cold
water must certainly sink in warm water.

Again if it be claimed that, owing to variation in evaporation,
warm surface water is at times denser than cold, while at other times
cold surface water is denser than warm, what must the consequences
be? Returning to the three alternative assumptions, if (a) were
true, the warmer water must have been the more dense during the
majority of hauls or solitary forms could not have been taken in
greater numbers from the warmer water. Yet, to obtain the aggre-
gate forms in greater numbers from the colder surface water, it
would have had to be the more dense’ during the majority of hauls.
Obviously both conditions could not have been realized, and even if
they could, the frequency of solitary forms would have paralleled their
abundance, which is contrary to fact.

If either (b) or (ec) were true, the situation, while more complex,
remains essentially unaltered. For in the first case, solitary forms
or short chains, being the heavier, would of necessity sink whenever
aggregate forms or long chains sank; while in the latter, aggregate
forms or long chains, being the heavier, would have to sink whenever
solitary forms or short chains sank.

ee

1918 | Michael: Behavior of Salpa democratica 271

It seems, then, that whatever the specific gravities of individuals
of either generation may be, and whatever may have been the way in
which viscocity of the water was related to high and low temperatures,
the observed differentials could not have been caused by changes in
viscocity alone. Furthermore, as any combination of physical influ-
ences could, at best, only directly affect one generation more than
the other, it follows that whenever the generation least Hable to be
affected was affected, the other generation must of necessity have been
similarly affected. This means that the observed differentials could
not have thus arisen. Is it not evident then, that, although changes
in viseocity, ete., have doubtless affected the magnitudes of the
observed differences in abundance of the two generations, such changes
alone are impotent to explain the differentials noted ?

D. THEORY OF LOCOMOTION

1. BEHAVIOR OF CHAINS

In the preceding pages it has been demonstrated that neither differ-
ences in season, differences in position, nor a combination of these,
nor variations in the condition of the water are adequate to account
for the facts that: (1) solitary forms are most abundant on the surface
when the temperature of the water is high; (2) aggregate forms are
most abundant on the surface when the temperature is low; and (3)
both solitary forms and aggregate forms are most frequent on the
surface when the temperature is low. Furthermore, tables 5 and 6
make it evident that influences associated with time of day could not
have given rise to these relations. Is the conclusion, then, not forced
upon one that, as stated on page 262, ‘‘the only type of behavior con-
sistent with all the facts is some form of locomotion’’? Since the com-
bined effects of all surface influences directly associated with time and
space, i.e., with time of day, day of the month, month of the year,
and with latitude and longitude, do not materially alter the observed
differentials, locomotion appears to be the only instrumentality by
means of which they could have arisen.

It is characteristic of all salpae, as stated on page 242, that when-
ever they breathe or feed they move forward along a stream of water
forced through their bodies. Concerning the movements of this
species (described as S. cabotti) Agassiz (1866, p. 18) says: ‘The

te University of Califorma Publications in Zoology [| Von. 18

chains* move along with the current, seemingly quite helpless, though
the upper extremity is sometimes deflected somewhat abruptly by at-
tempts to eseape capture. The solitary individuals, on the contrary,
are exceedingly active, swimming about vigorously, generally with the
anterior extremity uppermost; expelling by quick and powerful jerks
the water which propels them by its reaction. Their motions are very
similar to Trachynema; they can readily change the direction of their
movements, and regulate them by their powerful transverse muscular
bands, though they lack in their motions the ease and grace of Jelly
Fishes.’’ And again, on page 21: When the individuals of a chain
have become separated, ‘‘the aggregate form is perfectly helpless, the
great thickness of the tunic preventing it from regulating its motion ;
while, when connected as a chain, their capacity to guide the chain in
any particular direction is much greater.’’

Assuming, therefore, that protruding chains exist ; if the oral-atrial
axes of the chain salpae remain at an angle to the oral-atrial axis of
the soltary form after as well as before protrusion into the water
(see p. 244), the direction of locomotion of the solitary form will differ
from that of the protruding salpae. Moreover, as every salpa in the
left and right row respectively of the double chain, of necessity moves
in the same direction, the resultant foree tending to propel the chain
at an angle to the direction of motion of the solitary form will increase
as the number of protruding salpae increases. The mechanical result
must be either to break the chain or to twist it until solitary forms and
aggregate forms become headed so as to move in opposite directions.
The situation is that of a ‘‘tug of war’’ in which each short chain is
pulled along by the solitary form while, in each long chain, the solitary
form is pulled along by virtue of the combined locomotive power of the
attached aggregate forms.

As the number of salpae in the protruding chain increases, the
strain upon the chain also increases, and this must sooner or later
break it. Is there any clue as to how this occurs? There is. It was stated
on page 244 that the stolon undergoes alternating periods of active
segmentation and rest so that the salpae are formed, and, according to
Agassiz (1866, p. 20), set free in blocks of from forty to sixty indi-
viduals of nearly the same size. The ‘‘intermediate piece’’ (Johnson,
1910, p. 150) connecting two blocks is composed of small, imperfect,
and distorted individuals. In chains of Salpa fusiformis, which are

* Throughout these quotations Agassiz refers not to protruding chains but to
chains completely isolated from the solitary salpa.

1918] Michael: Behavior of Salpa democratica 273

formed in a very similar manner to those of S. democratica, Johnson
(1910, p. 151) says: ‘‘If one removes a large block from the chain,
the separation oceurs at the first zooid of the block, leaving the entire
intermediate piece as the terminal remnant of the block that remains.’’
The intermediate piece, or salpa adjacent to it, is therefore a place
of weakness, or ‘‘deploying point’’ as Johnson (1910, p. 151) calls
it, and it seems likely that, if not accidently broken sooner, the strain
above mentioned will naturally break a chain of S. democratica at this
point at about the time each block has been protruded into the water.
According to Agassiz (1866, p. 20), this separation must occur some
time before the entire block has been liberated, for, he says: ‘‘These
chains escape through an opening formed at the proper time through
the tunic . . . which shows afterwards no trace of the passage... .”’
If this be true, the load carried by the solitary form will vary period-
ically as budding proceeds, from zero at one extreme to the condi-
tion where the combined locomotive power of the aggregate forms
ereatly exceeds that of the solitary form at the other extreme.
Moreover, if as seems likely, the number of protruding salpae
required to equal in locomotive power that of the attached solitary
form are few, compared to the number in the protruding portion of a
block at the time of separation, long chains would be encountered more
frequently than short chains. Again, is it not probable that the large
majority of hauls encountering a number of long chains would also
encounter at least one and in some instances many liberated blocks,
chain fragments, or detached aggregate salpae, while the large majority
encountering a number of short chains would also encounter at least
one and in some instances many solitary forms from which no salpae
protruded? If this question be answered in the affirmative, and if it
be granted that the preference, so to speak, of solitary forms to remain
on the surface increases as the temperature of the water increases,
while that of aggregate forms increases as the temperature decreases,
it follows that long chains plus liberated blocks plus chain fragments
plus detached aggregate forms, would be most abundant and most
frequent in the colder surface water, while short chains plus detached
solitary forms would be most abundant but least frequent in the
warmer surface water. Finally, if each chain and liberated block and
chain fragment becomes broken up into its constituent salpae by the
swirl and pressure of the water during the process of towing (see
p. 260), it follows that the data, when tabulated as in the foregoing
tables, would reveal the solitary forms as most abundant and least

274 University of California Publications in Zoology [ Vor. 18

frequent on the surface when the temperature was 18°4C or more, and
the aggregate forms as most abundant and most frequent on the sur-
face when the temperature was 18°3C or less.

It is only by some such means of locomotion that I can conceive
how the observed differentials in abundance and great similarities
in frequency of the two generations could have arisen. Let it be
emphasized, however, that this is theory, not fact, and can be fully
established only by observations on moving protruding chains. But
if correct, verification ought not to prove difficult, for the theory
implies the same type of locomotion, though not the same type of
behavior relative to temperature, for every species within the genus
having similar double chains.

2. DEDUCED PECULIARITIES IN TEMPERATURE RELATIONS

If the foregoing theory of chain locomotion is correct, several con-
sequences in the distribution of the two generations are implied. It
is obvious that, were no solitary forms or aggregate forms ever
encountered except when attached together in chains, the frequency
of both generations would be identical with that of chains, and conse-
quently parallel to the abundance of chains. Whence, if long chains
accumulate on the surface in increasing numbers as the temperature
decreases, while short chains accumulate in increasing numbers as the
temperature increases, chains, irrespective of length, would be most
abundant and frequent in the coldest and in the warmest water, and
least abundant and frequent in water of medium temperature. There-
fore, if as the theory stipulates, the frequency of each generation is
consequent upon the characteristic occurrence of protruding chains,
the frequency of both should not only be nearly identical, but should
decrease as the temperature increases from its lowest to its middle
values, ie., from about 16°90C to about 18°5C, and then should
increase as the temperature increases from its middle to its highest
values, i.e., from about 1895C to about 21°0C. Furthermore, on
account of the periodic segmentation of the stolon resulting, hypo-
thetically, in periodic breakage of the protruding chains at the ‘‘inter-
mediate piece,’’ it follows, as stated on page 273, that long chains
would be encountered more frequently than short chains. Henee, if
M represent the temperature half way between the two extremes, and
x any range in temperature, the frequency of both generations relative
to M—zx should exceed that relative to M+-z.

1918] Michael: Behavior of Salpa democratica 275

Again, only one solitary form can be transported into cold surface
water by the aggregate salpae of each long chain, while several aggre-
gate forms must be transported into warm surface water by the soli-
tary salpa of each short chain. In other words, a decrease in number
of aggregate forms relative to an increase in temperature must be
masked by an increase in number of short chains to a far greater
extent than a decrease in number of solitary forms relative to a
decrease in temperature would be masked by an increase in number
of long chains. Therefore, aggregate forms should be more abundant
in the warmest surface water than in that somewhat cooler. Indeed,
their abundance should approximately parallel that of chains, so that
a minimum ought to oceur in water having a temperature about mid-
way between the two extremes, i.e., about 18°5C. Solitary forms,
however, being much less affected by the distribution of long chains
than aggregate forms are by that of short chains, should increase in
abundance as the temperature increases from its lowest, or nearly its
lowest, to its highest value.

By retabulating the data with reference to three, four, five, and
more temperature groups, this locomotion theory will be subjected to
an empirical test. To sum up, the relations that according to theory
should be revealed are:

1. Frequency of both generations nearly identical, and decreasing
with an increase in temperature to near the middle of its range, then
increasing with an increase in temperature.

2. Frequency of both generations greater in the lowest than in the
highest temperature group, greater in the next lowest than in the next
highest, greater in the third lowest than in the third highest, and so on.

3. Abundance of aggregate forms paralleling, or nearly paralleling,
frequency of both generations, appearing at its minimum relative to
medium temperatures.

4. Abundance of solitary forms decreasing as the temperature
decreases throughout the entire range or nearly so; if any increase in
abundance accompanies a decrease in temperature, this will be evi-
dent only in the coldest water when the number of temperature groups
is great enough to permit comparison of the effect of small ranges.

In table 11 the data are arranged in three groups according as
the temperature varied from 15°9C to 17°4C, 17°5C to 19°0C, or
19°1C to 20°6C. The only haul (1579) made in water exceeding
20°6C, and which did not capture a single individual of either genera-
tion, is excluded in order to preserve a uniform range in each group
of. 126C.

276 University of California Publications in Zoology [ Vou. 18

TABLE 11

Surface distribution of Salpa democratica during June and July,
1908 and 1909, relative to three temperature groups

Solitary forms Aggregate forms
Specimens Frequency Specimens Frequency
a)
Tempera- ‘3 ae 2 5B ake ie = =
ture in 2 ae Zz Ze = = ale heiiceees = = a 2s
digmie! Ge Ee eee Eee ge cee on eee er ae
15°9-17°4 15 9.0 7.9 465 52 88 97 7.9 5,750 640 88 97
17°5-19°0 42 all 1723) “25280 73 56 67 20.5 6,014 193 66 77
19°1-20°6 LS 143 WA AO 280 808i TOS I 21S 7 St

Each of the four conditions deduced from the locomotion theory
is shown by this table:

1. The frequencies of the two generations are identical relative
to the lowest temperature group, nearly so relative to the highest,
and parallel throughout. The frequency of both is lowest in water
of medium temperature (17°95C-19°0C).

2. The frequencies of both generations are greater in the coldest
than in the warmest water.

3. Abundance of aggregate forms parallels frequency of both gen-
erations, being highest (640 per hour) in the coldest water, and
lowest (193 per hour) in the water of medium temperature.

4. Abundance of solitary forms increases from 52 per hour in the
coldest water to 73 per hour in water of medium temperature to 280
per hour in the warmest water.

In table 12 the data are retabulated again in four groups according
to whether the temperature lay between 15°9C and 17°1C, 17°2C and
18°3C, 18°4C and 19°5C, or 19°6C and 20°8C. Be it noted that the
two middle groups each have a range of 1°2 C, while the two extreme

groups each have a range of 1°3C.

TABLE 12

Surface distribution of Salpa democratica during June and July, 1908
and 1909, relative to four temperature groups

Solitary forms Aggregate forms
Specimens Frequency Specimens Frequency
Sa
Tempera- ote a = 5 Be a 5B 5
ture in z 28 o.S = = © z 228 = z © =
centigrade S Se os = #4 a H Sioi = - 8
mn oe Se 1g Bun Eig is bEEeee eh mal ies a ee es
1529-1721 12 5.2 ©=6- 4.2 282 54 81 98 4.2 4,923 945 81 98
1722-1823 13) 148) A205 064s 72s SIS ale OMe ODS Somes ST
18°4-19°5 34. (27.0 15.7 3,107) 12) S765” 18-0) eo ie a ose ero
19°6—20°8 12 6.9 4.7 2,303 334 68 86 4.2 1123 163 61 81

1918 | Michael: Behavior of Salpa democratica Pa

As in table 11, each of the four conditions deduced from the loco-
motion theory appear in this table:

1. The frequencies of the two generations are identical in the two
lowest temperature groups, nearly identical in the highest temperature
group, and parallel throughout. The frequency of both generations
decreases as the temperature increases from its lowest to its middle
value (18°4C-19°5C), and then increases.

2. The frequency of both generations is greater in the coldest than
in the warmest water, and also greater in the next coldest than in the
next warmest water.

3. Abundance of aggregate forms parallels frequency of both gen-
erations, decreasing from a maximum (945 per hour) in the coldest
water to a minimum (115 per hour) in water between 18°4C and 19°5C
in temperature.

4. Solitary forms increase in abundance from 54 to 72 to 112 to 334
per hour as the temperature increases from its lowest to its highest
value.

In table 13 the data are once more retabulated relative to five
temperature groups according as the temperature lay between 15°9C
and 629°, 17 20C and 17°9C, 1820C, 1829C) 1920 and: 1929, or
20°0C and 20°8C. Be it noted, that although the lowest group has a
range of 1°1C and the highest a range of 0°9C, the range of each of
the three middle groups is one degree.

TABLE 13

Surface distribution of Salpa democratica during June and July,
1908 and 1909, relative to five temperature groups

Solitary forms Aggregate forms

Specimens Frequency Specimens Frequency

Tempera- 3 se 5 | oe 5 2

Merges fee Gee OS. 5.) aoe eee wes eee

centigrade & Be oe = H 6g H oe = H gi ee

pee Sete ey OS) 8 ee oe. sar aires eas al caesar
15°9-16°9 11 4.6 3.59 278 60 77 97 3.00 4,900 1,065 77 97
W/O SD ANG ale ssr/ as} 893 65 82 86 11.3 5,479 400 82 86
Wsc0=18°9 93 14:8 6:35. 1082; 73' 43) 158 6.4 460 31 43 58
19°0-19°9 16 15.4 10.8 2,200 143 70 Ti 13:6 2,913 189 88 89
20°0-20°8 10 6.1 4.7 PBIB Byte e7f ale ab 123 184 69 86

Once again are each of the four conditions deduced from theory,
revealed :

1. The frequencies of the two generations are identical relative
to the three lowest temperature groups, and decrease as the tempera-

278 University of California Publications in Zoology [ Von. 18
{

ture increases from its lowest to its middle value (18°0C-18°9C)
where the minimum, 58, occurs. Relative to the two remaining groups
the frequency of solitary forms increases from 71 to 91 as the tempera-
ture increases, while that of aggregate forms decreases from 89 to 86.
Be it noted that the former increase accords with theory, while the
latter less significant decrease does not.

2. The frequency of both generations in the coldest water exceeds
that in the warmest, and that of solitary forms in the next coldest water
exceeds that in the next warmest by 1586-71, while the correspond-
ing frequencies of aggregate forms, 86 and 89, are reversed in order.
Here again, the former excess which aecords with theory, is much more
significant than the latter deficiency which does not accord with theory.

3. Except for an insignificant decrease from 189 to 184 aggregate
forms per hour relative to the two highest temperature groups, their
abundance parallels the frequency of solitary forms exactly. Is it not
striking that the abundance of 400 per hour relative to the next lowest
group, exceeds significantly that of 189 per hour relative to the next
highest group, which accords with theory, while all the relations not
in accord with theory are comparatively insignificant, 1.e., the decrease
from 89 to 86 in frequency of aggregate forms and from 189 to 184
in their abundance instead of an increase relative to the two highest
temperature groups; and the deficiency instead of an excess in fre-
quency of aggregate forms (86) relative to the next lowest temperature
group as compared to that (89) relative to the next highest group ?

4. Solitary forms increase in abundance from 60 to 65 to 73 to 143
to 378 per hour as the temperature increases from its lowest to its
highest value.

Attention is called to the fact that the abundance of solitary forms
relative to the next lowest temperature group (as given by tables 11,
12, and 13) has deercased from 73 to 72 to 65 per hour as the number
of groups has been increased from 3 to 4 to 5. Obviously, this accords
with the fact that solitary forms decrease in abundance as the tem-
perature of the water decreases. But, the abundance of solitary forms
in the coldest water has increased from 52 to 54 to 60 per hour as the
number of groups has been increased from 3 to 4 to 5. Apparently,
this fact carries an implication directly contrary to the above. But,
it accords with the theory of chain locomotion. For, does this theory
not stipulate that a larger number of solitary forms should be encount-
ered in the coldest water than would be present were they not pulled
there by virtue of the combined locomotive power of the aggregate

1918 | Michael: Behavior of Salpa democratica 219

forms in each of a number of long protruding chains? Do the facts
not suggest that, if retabulated again relative to temperature groups
of still smaller range, the data may reveal an excess in abundance of
solitary forms in the coldest water over that in next coldest? Accord-
ingly, table 14 is supplied, in which the data are retabulated with
respect to six temperature groups each having a range of 0°8C.

TABLE 14

Surface distribution of Salpa democratica during June and July,
1908 and 1909, relative to six temperature groups

Solitary forms Aggregate forms
Specimens Frequency Specimens Frequency
pase Sy

Tempera- iS 36 B ty Cale, La] u

site in ae 28 2 al = eS © a zZ ae = e © z

centigrade 5 Be 593 = a qd 8 Soe = a Gok

Fe ate lie). = eo AB & Has a Ay Be

WSO UGES 30) Bats 278 68 86 99 3.55 4.900 1,195 86 99
16°7-17°4 5 49 4.4 187 38 90 91 4.4 850 174 90 91
1725-1822 14 10.8 8.3 881 HU tid) teh) 4,825 447 77 85
18°3-19°0 28 20.3 9.0 1,399 69 44 55 12.2 1,189 59 60 71
19°1-19°8 9 8.5 6.7 gfe} PAty 7/8) tik LY 1,988 234 79 81
19°9-20°6 9 D8 ALT 2,303 398 81 93 4:2 1,123 194 72 86

Once again is each of the four conditions deduced from the loco-
motion theory evident, though not so strikingly, perhaps, as in the fore-
going tables:

1. The frequencies of the two generations are identical relative to
the lowest, second lowest, third lowest, and second highest temperature
groups, and they are parallel throughout. The frequency of both
decreases as the temperature increases from its lowest to its middle
value (18°3C to 19°0C), and then increases as the temperature
increases to its highest value.

2. Both generations appear more frequently in the coldest than
in the warmest water, in the second coldest than in the second warmest
water, and in the third coldest than in the third warmest water.

3. The abundance of aggregate forms, while more erratic than
shown by the foregoing tables, parallels in general the frequency,
being greatest (1195 per hour) in the coldest water and least (59 per
hour) in water having a temperature between 18°3C and 19°0C.

4. Except that slightly less, instead of more, than 81 solitary forms
per hour were obtained when the temperature was between 18°3C
and 19°0C, they increase in abundance as the temperature increases
from next to its lowest to its highest value. Is it not a significant cor-

280 University of California Publications in Zoology [ Vou. 18

roboration of theory that more per hour were obtained in the coldest
than in the next coldest water?

Although the hauls are too few and the temperature range in each
group is too small to justify retabulation relative to a still smaller
range, it is found that the abundance of solitary forms relative to
temperatures between 15°9C and 16°5C is 75 per hour, while that
relative to temperatures having the same range (0°7C) between 16°6C
and 17°2C is 36 per hour. That the significance of this fact may be
better appreciated, the abundance of solitary forms and mean tem-
peratures relative to the two lowest temperature groups as shown by
tables 11, 12, 13, and 14 are brought into relation to the fact just
mentioned in the following lists:

List A GROUPS List B

(Lowest temperature group) (Next lowest temperature group)
ae

Mean Mean Abundance
temperature _ Abundance temperature

16°65C 52 3 18°39C ie

16°52 54 4 L755 72

16°46 60 5 17 258 65

16°44 68 6 17°08 38

16°43 75 7 17°00 36

Presented in this way, list A shows that solitary forms decreased
in abundance as the mean temperature increased from 16°43C to
16°65C, while list B shows that they increased in abundance as the
mean temperature increased from 17°00C to 18°39C. How is this
apparent paradox to be explained except on the assumption that the
number of solitary forms with long protruding chains exceeded the
number of detached solitary forms plus the number with short pro-
truding chains when the temperature of the water was on the average
below 16°7C, while when it was above 16°29C, the number of detached
solitary forms plus the number with short protruding chains exceeded
the number with long protruding chains?

Is it not striking that the relations revealed by tables 11 to 14
verify the deductions from the theory of chain locomotion almost to
the smallest detail? In order that this may be better visualized, the
relation between the two generations in abundance and frequency is
presented in the form of histograms by plates 10 and 11, figures 4
to dal.

1918] Michael: Behavior of Salpa democratica 281

5. VALIDITY OF THE PLANKTON CONCEPT

This is too large a subject to discuss fully, but the assumption of
passivity, and consequently of uniformity, in plankton distribution
so permeates the literature as to demand brief consideration in the
light of the facts revealed by this investigation. The fundamental
tenet of the prevailing plankton concept is, as later demonstrated, that
the organism is carried about passively by the currents of the sea;
that the organism plays a negligible part in its own distribution.
Virtually, the inanimate is substituted for the animate, and the prob-
lem of plankton distribution thus becomes nothing more than a
problem in mechanies; a problem resembling that of the distribution
of dust in the air, or of salts in the sea; a complicated problem, per-
haps, but none the less a mechanical one.

This may be better appreciated, perhaps, from an analogy. Rain-
drops tend to be uniformly distributed. In any particular region
where the physical conditions of the air are the same, approximately
the same number of raindrops fall on one square foot of the earth’s
surface as upon any other square foot, whence a single rain gauge
is sufficient to measure quite accurately the total precipitation through-
out that entire region. This is common knowledge. It is also com-
mon knowledge that the locomotive powers, say of small gnats, are too
feeble to permit headway against the wind; they are carried hither
and thither by the currents of the air. Let it be assumed that they
are carried passively, that their own activities are negligible, and
they must of necessity be distributed in a very similar manner to
raindrops, or better to the dust of the air. In other words, wherever
in the air the physical conditions were uniform, there also the abun-
dance of gnats would approximate uniformity.

Of course this sounds ridiculous, but it is the unesecapable con-
sequence of an assumption of passivity. It is only necessary, there-
fore, to substitute plankton organisms for gnats and water for air
to realize that, if the fundamental tenet of the plankton concept be
true, there is no escape from the claim made by Johnstone (1908,
p. 157) that ‘‘the validity of all conclusions as to the general abun-
dance of microscopic life in the sea depends on the truth of the
postulate, that wherever in the sea the physical conditions are uni-
form, there also the composition and abundance of the plankton is
uniform.’’ This postulate of uniformity, although rightly held by
many to be absurd, either must be true or else the fundamental tenet

282 University of California Publications in Zoology [ Vor. 18

of the plankton concept must be false. Any given plankton species
must either control its own distribution to a significant extent or it
must tend to be distributed in accordance with the uniformity
postulate, i.e., like the salts of the sea.

That this postulate actually does lie at the foundation of a large
amount of quantitative plankton research is evident from the extent
to which what might be called ‘‘rain gauge’’ methods of collecting
are employed. Sweeping statements are not infrequently made rela-
tive to the distribution of plankton organisms over large areas of the
sea which are based upon the assumption, more or less unrecognized
perhaps, that owing to passivity and consequently to uniformity, one
or at most a very few hauls, carefully made with a net whose ‘‘filter-
ing capacity
(Michael, 1916, pp. xvi-xix). Maps and charts are continually being
published showing the distribution of various so-called types of plank-

93

is accurately determined, justifies the generalizations

ton throughout large portions of the globe, the reliability of which,
with few exceptions, rests upon rain gauge methods of collecting,
which methods in turn, of course, depend upon the validity of the
eencept of passivity and uniformity.

Nothing is more natural, perhaps, than to fall into the error of
supposing that, because the locomotive powers of many plankton
organisms are too feeble to permit headway against a current, there-
fore locomotion has a negligible effect on the distribution of such
organisms. In thus overlooking the fact that the ocean, being a
body of three instead of two dimensions, may permit plankton organ-
isms with feeble powers of locomotion to control their horizontal dis-
tribution by means of vertical movements, it is not surprising to find
that such organisms are generally regarded, so far as concerns their
horizontal distribution, as physical particles which are carried hither
and thither by wave, tide, and current. In spite of the noteworthy
investigations of the Port Erin Marine Biological Station, Isle of
Man, as well as those of various individuals, which have established
facts wholly inconsistent with this conception, it not only persists but
is made apparent in almost every standard text or reference book
dealing in any way with plankton organisms.

Witness, for example, the following opening statement quoted
from Steur’s Planktonkunde (1910, p. 1): ‘‘Die Planktonkunde oder
Planktologie befasst sich mit der Erforschung jener im freien Wasser
schwebenden,* grossenteils mikroscopischen Lebenwesen, die wir heute

* Italics in this and two following paragraphs inserted by author.

1918 | Michael: Behavior of Salpa democratica 283

mit dem Namen Plankton bezeichnen.’’ In order that there be no
doubt as to the real meaning of Steur’s words, consider the following
statement, also quoted from page 1: ‘‘Die Planktonorganismen oder
Planktonten sind also grésstenteils kleine Lebenwesen, die ohne Eigen-
bewegung oder ungeachtet derselben hilflos im Wasser treiben

und die Planktologie ist demnach die Lehre von den schwebenden
Wasserorganismen.’’ Compare with these statements, the following
extracted from the first page of Schurig’s Plankton-Praktikum (1910) :
‘“Unter Plankton nun versteht man die Gesammtheit aller meist
mikroseopisch kleinen im Wasser schwebenden, ‘flottierenden’ Leben-
wesen pflanzlicher und tierischer Natur, die dem Wogen keinem
Widerstand entgegenzusetzen vermogen, die einem NSprelball der
Wellen reprasentieren.”’

That the extent to which this conception has guided the thinking
of able investigators may be more fully appreciated, the following
statements are quoted from Johnstone, Conditions of life in the sea
(1908) :

From page 56: ‘‘There are first of all those [organisms] which
by reason of their minute size and feeble powers of locomotion are
carried about passively in the sea by tides and currents. These are
they which are caught in the tow-nets, which Miller called the Auf-
trieb, and Hensen the Plankton.’’ Again, from page 57: ‘*Then
one at times finds it difficult to say whether organisms, like the
medusae, which are carried about in great swarms by tides and cur-
rents, but which nevertheless are capable of some degree of locomotion,
are to be included in the plankton or in the nekton.’’ Or again, from
page 65: ‘‘Some worms may belong temporarily at least to the nekton,
and the large medusae, though perhaps better classed with the plank-
ton, do move about ‘of their own accord.’’’ Or again, from page 67:
‘“These [pelagic fish eggs] have absolutely no powers of locomotion
and they are drifted about passively by tides and currents, the very
type of planktonic organisms.’’ Or again, from page 143: ‘‘ Plank-
ton organisms . . . have little powers of locomotion, certainly not such
as will enable them to segregate themselves, and they are drifted about
Or lastly, from page 148: ‘‘Small

?

in the sea quite passively.’

’ organisms, such as those of the plankton, are particles in the physical

sense and behave as such.’’

Clearly, Johnstone (1908) has recognized
the real nature of the plankton concept; similar statements might be

quoted from nearly every page of his book.

284 University of Califorma Publications in Zoology | VoL. 18

This is not all. The same conception, or should it be called a mis-
conception, is to be found, expressed more cautiously perhaps, not
only in the technical writings, textbooks, and laboratory manuals,
but also in most of the semipopular books and reference books that
treat plankton organisms to any extent whatsoever. To cite but three
instances: Hickson (1893, p. 52), in his Fauna of the deep sea, says:
‘‘Some animals simply float or drift about with the currents of the
sea and aré unable to determine for themselves, excepting, perhaps,
within very small limits, the direction in which they travel. ... This
portion of the fauna has recently been called the Plankton.’’ Again,
Arnold (1908, p. 23) in her Sea-beach at ebb-tide, says: ‘‘Those
[organisms] which float at or near the surface and are carried about
by the currents... are plankton. Strong swimming animals which
move about at will are nekton.’’ Finally, on page 702 of the New
International Encyclopaedia (1916), one finds this statement: ‘‘In
zoology the term [plankton] is restricted to the pelagie life which
drifts, the actively swimming surface forms constituting a separate
assemblage, the nekton. It consists mainly of jelly fishes, ascidians,
especially salpa, and a great variety of pelagic larvae and minute
erustacea with feeble powers of locomotion that are carried along
almost passively by the oceanic currents.”’

This list of quotations might be continued almost indefinitely. All
carry the implication, some more conspicuously than others, that
plankton organisms, because of their feeble powers of locomotion, —
may be assumed to behave like corks; that the characteristic quality
of such organisms is to float, to drift, to remain in suspension. It
may be, perhaps, that few actually believe this; it is difficult to under-
stand how anyone ean believe it. Yet, the above list of quotations
makes it certain that it is precisely this ridiculous assumption that
lies at the foundation of the prevailing plankton concept; that it
colors the thinking of able biologists; and that it influences the pro-
cedure of capable investigators.

There are, to be sure, a few text books, a few reference books, a
few semipopular books treating of plankton that are not permeated
by this dogma, but the number. is remarkably small. On page 309
of Murray and Hjort’s Depths of the ocean (1912), this statement
occurs: ‘‘The term ‘plankton’ is now used for all floating organisms
which are passively carried along by currents, while ‘nekton’.. .
is used to designate all pelagic animals which are able to swim against
currents.”’ Although this statement carries the same implication,

1918 | Michael: Behavior of Salpa democratica 285

the ensuing discussion partly offsets it. Witness, for example, the
following from page 773: ‘‘Hensen invented his method for the pur-
pose of investigating the floating or suspended life in the sea, which
he termed ‘plankton.’ This plankton is, however, very difficult to
define, for among the profusion of organisms, ranging from the
minutest plants ... to the large crustaceans and fishes, there is an
enormous variety in size, in activity, and consequently in the faculty
of avoiding the appliances of capture. In many investigations, there-
fore, the word plankton may be taken to signify practically ‘the catch
made in the hoop-net constructed by Hensen, when new and in per-

of rhe}

feet working order. A further step in the same direction is taken
by Fowler (1912, p. 162) in his Science of the sea: ‘‘To those animals
and plants which float in the sea, whether at the surface or in deep
water, the term ‘Plankton’ is applied for brevity ; they are contrasted
with the creatures which crawl upon, or are fixed to, the bottom. In
modern usage, Plankton is generally taken to include even powerful

swimmers . . . as well as helpless and minute organisms.’’ Similarly,

ce oh)

under the term ‘‘plankton’’ in the last edition of the Encyclopaedia
Britannica, Fowler (1911, p. 720) writes: ‘‘Plankton, a name invented
by Professor Victor Hensen for the drifting population of the sea.’’
But, in the next column: ‘‘The fauna of the sea is divisible into the
plankton, the swimming or drifting fauna which never rests on the
bottom (generally taken now to include E. Haeckel’s nekton, the strong
swimmers such as fish and cephalopods), and the benthos, which is
fixed to or crawls upon the bottom.”’

Although these statements, quoted from Fowler (1911, 1912) and
from Murray and Hjort (1912), represent a decided step in advance,
they still carry the implication that a large number of plankton
organisms are as helpless as drifting physical particles; that they play
a negligible part in their own distribution. There may be such
organisms, but ought this not to be demonstrated rather than assumed ?

Is it beyond question that even fish eggs are of necessity distributed
in accordance with this assumption? At a depth of twenty fathoms
two eggs begin development at the same time and place; the rate of
growth is more rapid in one; it’s specific gravity decreases and it
ascends, reaching the surface by the time the second, more slowly
developing, egg has ascended to the fifteen fathom level. The surface
current flows southward; that at fifteen fathoms, to the west of south.
At the end of two days the two eggs are ten miles apart. Has the
difference in their rates of growth played a negligible part in deter-

286 University of California Publications in Zoology [ Von. 18

mining their whereabouts? Does this self-induced movement—the
locomotion of the egg—count for nothing in its distribution? Is the
egg carried along passively by the current?

It would seem necessary, in the hght of this investigation, to
discard completely this dogma of passivity, and to replace it by a
conception more in accordance with fact. For Salpa democratica is
admitted by all to be a most typical plankton organism, and, if the
facts revealed in the foregoing pages are trustworthy, it is evident
that this plankton species, to a very large extent, does control its
own distribution. It is not drifted about passively ; it is not a particle
in the physical sense and it does not behave as such. How explain
the differentials in distribution of the two generations on any such
basis? The hauls were the same; the currents were the same; the
tides were the same; every conceivable condition of and in the sea
was the same, during the collecting of one generation as during the
collecting of the other. Yet they were distributed differently. Ob-
viously, the activity of the organisms and that alone can have caused
the differentials in their distribution. Further, the data strongly
suggest that the main type of activity involved is locomotion. If
so, it necessarily follows, not only that this plankton species influ-
ences its own distribution, but that it does so just as certainly, just
as definitely, and by much the same means as does any fish or other
animal ineluded under the general term, nekton.

Salpa probably does not accomplish this by forcing its way against
a current as does a fish, but the solitary forms manage to get them-
selves onto the surface in largest numbers when the temperature of
the water is high and to avoid the surface when the temperature is
low, while the reverse is true of the aggregate forms. Even granting
them to be transported by surface currents, as they doubtless are,
these data demonstrate that solitary forms are found for the most
part in the warm currents and aggregate forms in the cold currents.
Is it not, therefore, as illogical to credit the entire control of their
horizontal distribution to the currents as it would be to claim that John
Smith had nothing whatever to do about getting himself to New York
because he was earried there on a Pennsylvania Pullman?

Fom a strictly biological point of view, it would seem necessary to
disregard entirely, as Fowler (1911, 1912) has done, the distinction
between plankton and nekton. There seems to be no natural line of
demarcation between the two. Surely, there is far less difference in
activity between sardines and jelly fishes or the larger copepods than

1918 | Michael: Behavior of Salpa democratica 287

there is between a copepod and a fish egg or diatom. Yet sardines are
excluded from the plankton, while everything from a diatom to a
jelly fish is ineluded.

Or consider the matter from another point of view; the sardine
begins its career as an egg; by a gradual and continuous process of
growth the successive stages in the life cycle follow: the early embryo,
the late embryo, the young larva, the mature larva, the post larva,
the adult. Clearly, activity characterizes the individual from egg to
adult. At what stage does the sardine cease to be a constituent of
the plankton and take its place with the nekton? At what stage does
its activity become effective in determining its distribution? It was
suggested on page 285, how activity might be effective in the egg. If
so, can any differential in the type of locomotion or the degree of its
effectiveness be recognized that will justify a distinction between
plankton and nekton on that basis? Some say that strong swimmers
belong to the nekton and that such animals alone are able to make
headway against a current. But, how strong is a strong swimmer, and
against a current of what velocity must headway be made? Merely
to raise this question denotes the artificiality of such a distinction.
With equal justification might we not distinguish between the plank-
ton and nekton of the air, defining the latter as strong flyers capable
of making headway against the wind?

However, in spite of the artificiality of distinguishing between
plankton and nekton, the distinction does have a certain methodo-
logical value. Might it not be wise, therefore, to combine the state-
ments of Fowler (1911, 1912) and of Murray and Hjort (1912) into
a definition somewhat as follows? Marine and fresh water organisms
are divisible into two main classes: (1) pelagic organisms, the fauna
and flora that do not live upon, or fixed to, the bottom; and (2) ben-
thos, or the fauna and flora which do live upon, or fixed to, the bot-
tom. For practical reasons pelagic organisms are artificially subdivided
into two groups: (1) plankton, or the sum total of all animals and
plants captured by any kind of tow-net or water-bottle; and (2)
nekton, the sum total of all animals that escape capture by such
means. Does not a statement of this nature serve the purpose of dis-
tinguishing the two types of organism, insofar as there are two types,
without committal as to whether or not any particular ones play an
important part in controlling their own distribution ?

iw)
oe)

8 University of California Publications in Zoology —— [ Vou. 18

E. SUMMARY AND CONCLUSIONS

The facts revealed by this investigation may be summarized under

three heads as follows:

I. Facts relating to seasonal distribution :

1. The occurrence of Salpa democratica in the San Diego region
at all depths during 1908 and 1909 reached its maximum in the
summer, both generations being restricted almost exclusively to
the months of June and July.

2. Both generations were more abundant on the surface during
June than during July.

3. Aggregate forms were more abundant than solitary forms
during June, while solitary forms were the more abundant during
July.

Il. Facts relating to vertical distribution:

1. Solitary forms are most abundant on the surface, decreasing
in abundance as the depth increases.

2. Aggregate forms are most abundant in the neighborhood
of five fathoms, decreasing in abundance as the depth increases
below that level.

3. Aggregate forms were, on the average, more abundant than
solitary forms at all levels.

4. Individuals of neither generation have been captured below
seventy-five fathoms.

III. Facts concerning surface distribution during June and July,
1908 and 1909 relative to temperature of the water:

1. When the data are tabulated with respect to two tempera-
ture groups ranging in value from 15°9C to 18°3C and from
18°4C to 20°8C respectively, they show that:

a. Solitary forms are most abundant but least frequent
in the warmer water.

b. Aggregate forms are most abundant and most frequent
in the colder water.

e. The frequency of solitary forms in both warm and cold
water is nearly identical with that of aggregate forms.

d. These same relations hold when all the June and July
data are considered, when day hauls alone are considered,
when night hauls alone are considered, when only hauls made

1918 | Michael: Behavior of Salpa democratica 289

between 6 a.m. and 10 a.m. are considered, when only hauls
made between 10 A.M. and 2 p.m. are considered, when only
hauls made between 6 p.m. and 10 p.m. are considered, when
all hauls are excluded except those made during June, 1909,
and when all are excluded except those made between June 15
and June 29, 1909, and within one mile of each other.

2. When the data are tabulated with respect to three, four, five,
and six temperature groups each having an equal range between
15°9C at one extreme to 20°8C at the other, they show that:

a. Solitary forms increase in abundance as the temperature
increases from its lowest, or next lowest, value to its highest
value.

b. The frequeney of both solitary forms and aggregate
forms decreases as the temperature increases from its lowest to
its middle values, and then increases as the temperature
increases.

e. Both solitary forms and aggregate forms are more fre-
quent in the coldest than in the warmest water, more frequent
in the next coldest than in the next warmest water, more fre-
quent in the third coldest than in the third warmest water, and
So on.

d. The abundance of aggregate forms parallels the fre-
queney of both generations.

3. When each of the June and July surface hauls is examined
on its own merits, it is found that :
a. Forty-six of the forty-nine hauls that captured solitary
forms also captured some aggregate forms.
b. Twenty-four of the twenty-seven hauls that failed to
capture solitary forms also failed to capture aggregate forms.

From these facts it is concluded that:

1. Differentials in distribution of solitary forms and aggregate
forms are as definite and pronounced as are the differentials in their
structure.

2. Seasonal succession of the two generations can not explain
the observed differentials.

3. Greater production of solitary forms in stratified areas of warm
surface water than in those of cold surface water, if occurring at all,
ean not explain the observed differentials.

290 University of California Publications in Zoology [ Vou. 18
Y¥ / gu

4. No amount of hydrographic change or of variation in viscocity
of the water can explain the observed differentials.

5. Solitary forms show an increasing preference, so to speak, for
the surface, as the temperature of the surface water increases from
16°C to 20°C; while aggregate forms show a similar preference as the
temperature decreases.

6. The chain of aggregate forms remains attached to the solitary
salpa after having been liberated from its mantle cavity into the
water.

7. One solitary form is carried into cold surface water by virtue
of the combined locomotive power of the aggregate forms in each long
protruding chain, while short chains are carried into warm surface
water by virtue of the locomotive power of the attached solitary form.

8. Owing to the strain due to the opposite direction of locomotion
of solitary form and of attached aggregate forms, the protruding
chain becomes detached from the stolon periodically, 1.e., at the ‘‘inter-
mediate piece’’ before an entire ‘‘block’’ of aggregate forms has been
protruded.

9. Contrary to the prevailing plankton concept, Salpa democratica,
a typical plankton organism, controls to a significant extent its own
distribution just as certainly as does any fish or other animal com-
monly included under the term of nekton.

It is unnecessary to state that the sixth, seventh, and one con-
clusions, while apparently unescapable, are all based upon indirect
evidence and must be regarded as tentative rather than as fully estab-
lished. In conclusion, if this paper serves to stimulate a closer
morpho-physiological scrutiny of the life cycle of the Salpae, if it
serves to instigate a closer study of their habits, if it serves to rectify
a prevailing misconception concerning plankton distribution, and if
it serves as an antitoxin against the too prevalent tendency of morph-
ologists to ignore the ecologist’s point of view and of ecologists to
ignore the morphologist’s point of view, its primary aim will be
accomplished.

Transmitted July 10, 1917.
Scripps Institution for Biological Research,
La Jolla, California.

1918 | Michael: Behavior of Salpa democratica 291

F. LITERATURE CITED
ANONYMOUS
1916. Plankton. New Inter. Eneye. (New York, Dodd), 18, 702.

AGASSIZ, A.
1866. Description of Salpa cabotti Desor. Proc. Boston Soc. Nat. Hist., 11,
17-23, figs. 1-5 in text.

ARNOLD, A. F.
1903. The sea-beach at ebb-tide, a guide to the study of the seaweeds and
lower animal life found between tide-marks. (New York, Century
Co.), x + 490 pp., 600 figs. in text.

Brooks, W. K.
1893. The genus Salpa. Mem. Biol. Lab. Johns Hopkins, 2, 397 pp., 57 pls.

ESTERLY, C. O.

1912. The occurrence and vertical distribution of the Copepoda of the San
Diego region, with particular reference to nineteen species. Univ.
Calif. Publ. Zool., 9, 253-340, 7 figs. in text.

Fow.er, G. H.

1911. Plankton. Encye. Brit., ed. 11, 21, 720-725, 3 figs. in text.

1912. Science of the sea. (London, Murray), 452 pp., 221 figs. in text.
HERDMAN, W. A. :

1889. Report upon the Tunicata collected during the voyage of H. M. 8.
‘¢Challenger’’ during the years 1873-1876. Part 3, Rep. Sci. Res.
‘“Challenger,’’ Zool., 27, no. 4, 166 pp., 11 pls.

Hickson, S. J.
1893. The fauna of the deep sea. (London, Triibner), xi + 169 pp., 23 figs.

JOHNSON, M. E.
1910. A quantitative study of the development of the salpa chain in Salpa
fusiformis-runcinata. Univ. Calif. Publ. Zool., 6, 145-176, 15 figs.
in text.

JOHNSTONE, J.

1908. Conditions of life in the sea, a short account of quantitative marine
biological research. (Cambridge University Press), xiii + 332 pp.,
31 figs. in text.

LEuUCKART, R.

1854. Zur Anatomie und Entwicklungsgeschichte der Tunicaten. Zoolog-
ische Untersuchungen. (Giessen, Ricker), 2, 93 pp., 2 pls., 3 figs. in
text.

McEwen, G. F.

1916. Summary and interpretation of the hydrographic observations made
by the Scripps Institution for Biological Research of the Uni-
versity of California, 1908-1915. Univ. Calif. Publ. Zool., 15, 255-
456, pls. 1-38.

MIcHAEL, E. L.
1911. Classification and vertical distribution of the Chaetognatha of the
San Diego region, including re-descriptions of some doubtful
species of the group. Ibid., 8, 21-174, pls. 1-8.
1916. Dependence of marine biology upon hydrography and necessity of
quantitative biological research. Jbid., 15, i—xxiii.

292 University of Califorma Publications in Zoology [ Vou. 18

MicHakg.L, HE. L., and McEwsn, G. F.

1915. Hydrographic, plankton, and dredging records of the Scripps Insti-
tution for Biological Research of the University of California,
1901-1912. Ibid., 15, 1-206, 4 figs. and 1 map in text.

1916. Continuation of hydrographic, plankton, and dredging records of the
Seripps Institution for Biological Research of the University of
California, 1913-1915. Ibid., 15, 207-254, 7 figs. in text.

Morray, J., and Hgort, J.

1912. The depths of the ocean, a general account of the modern science of
oceanography based largely on the scientific researches of the
Norwegian steamer ‘‘ Michael Sars’’ in the North Atlantic. (Lon-
don, MacMillan), 821 pp. 575 figs. in text.

RITTER, W. E.

1905. The pelagic Tunicata of the San Diego region, excepting the Larvacea.

Univ. Calif. Publ. Zool., 2, 51-112, pls. 2-3, 31 figs. in text.
Scuuriec, W.

1910. Hydrobiologisches und Plankton-Praktikum. (Leipzig, Quelle), 160

pp., 6 pls., 215 figs. in text.
SEELIGER, O.

1886. Die Knospung der Salpen. Jena. Zeitschr. Naturw., 19, 573-677,

10 pls.
SHULL, A. F.

1911. Studies in the life cycle of Hydatina senta. II. The réle of tempera-
ture, of the chemical composition of the medium, and of internal
factors upon the ratio of parthenogenetic to sexual forms. Jour.
Exper. Zool., 10, 117-165.

STEUER, A.

1910. Planktonkunde. (Leipzig, Teubner), 723 pp., 365 figs. in text.
WHITNEY, D. D.

1907. Determination of sex in Hydatina senta. Jour. Exper. Zool., 5, 1-26.

EXPLANATION OF PLATES

«PLATE 9
Fig. 1. Dorsal view of a portion of a protruded chain of Salpa democratica.
x 18.

Fig. 2. Ventral view of a mature individual of the solitary generation.
x 4.5.

Fig. 3. Dorsal view of aggregate form containing a nearly mature embryo
of the solitary generation. X 4.5.

| 294 |

UNIN SCAR PUBE RZOOE VOEN ls [MICHAEL] PLATE 9

PLATE 10

Fig. 4. Histograms showing abundance of aggregate forms, or number
obtained per hour from the surface relative to temperatures between 15°9C and
18°3C (left), and 18°4C and 20°8C (right); (a) based on all data pertaining to
June and July, 1908 and 1909 (table 4); (b) based on night data (table 5); (c)
based on day data (table 6A); (d) based on intense light data (table 6B); (e)
based on early morning data (table 6C); (f) based on evening data (table 6D);
(g) based on June, 1909 data (table 8); (h) based on data restricted to collec-
tions made within one mile of each other (table 10).

Fig. 5. Histograms showing abundance of solitary forms relative to the same
conditions as specified in the explanation of figure 4.

Fig. 6. Histograms showing abundance of aggregate forms on the surface
relative to temperatures between 15°9C (left) and 20°8C (right), divided into (a)
three groups each having a range of 1°6C (table 11); (b) four groups each having
a range of 1°2C or 1°3C (table 12); (c) five groups each having a range of one
degree (table 13); and (d) six groups each having a range of 0°8C (table 14).

Fig. 7. Histograms showing abundance of solitary forms relative to the same
conditions as specified in the explanation of figure 6. ,

[ 296 ]

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Fig. 8. Histograms showing frequency of aggregate forms, or percentage of
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conditions as specified in the explanation of figure 4.

Fig. 9. Histograms showing frequency of solitary forms relative to the same
conditions as specified in the explanation of figure 4.

Fig. 10. Histograms showing frequency of aggregate forms relative to the
same conditions as specified in the explanation of figure 6.

Fig. 11. Histograms showing frequency of solitary forms relative to the
same conditions as specified in the explanation of figure 6.

[ 298 ]

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Description of Bufo canorus, a New Toad from the Yosemite National Park,

Ou

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7. The Subspecies of Sceloporus. occidentalis, with Description of a New Form
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_. Lizards, by Charles Lewis Camp. Pp. 63-74. December, 1916 -...-...........----
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Holden. Pp. 75-114, plates 5-12, 18 text figures. March, 1917 ................-
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_ “UNIVERSITY OF CALIFORNIA PUBLICATIONS
Dr 5 IN

3 ZOOLOGY
Vol. 18, No. 13, pp. 299-336, plates 12-13, 6 figures in text Apri] 20, 1918

A QUANTITATIVE ANALYSIS OF THE
MOLLUSCAN FAUNA OF SAN
FRANCISCO BAY

BY

E. L. PACKARD

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UNIVERSITY OF CALIFORNIA PUBLICATIONS
IN

ZOOLOGY
Vol. 18, No. 13, pp. 299-336, plates 12-13, 6 figures in text April 20, 1918

A QUANTITATIVE ANALYSIS OF THE
MOLLUSCAN FAUNA OF SAN
FRANCISCO BAY

BY
E. L. PACKARD

CONTENTS

PAGE

Haat O CLULC: ENO Tannen eee MRE ok Se eee ee ee. 299
Generaledistrbnmimonot the Mollusca 2. -. - = eee ee ee 301
iiysiealecharaciers) Ol San Hrameis@or ay, sees se ees seers eee eee ecee cane 301
Mheemollnscanmmianuma Ot Sana Bramieis Co) iB aya ses ees tree ee 303

iC OMGMIMemCOMSTG le tlONS! csc ce.. he Se ee ater es ee me nee ee 308
Factors governing the distribution of the Mollusca __.....-..--..--------------e-ee--------- oT
Vea OMMR OMG CpG) y cocci ee i a a ek ee a a 318
Vel eae O mat Om haya Cte fay Ott Omnis me Aces tee see ame oe ee ee 318
TRG erly oy eCay SFU do en re ge ee Ae ce ee ee ere eee yA
elationisGOr vem erat Gu hese coke cease eens eet ea cee ee ete 8 ee Oe
Relation tomer avian) al emt OO Gs Stuttg mecca teen eee eee eee eee TL
Ace ert Oe t Obie oO tse Wav: OTN mn Eppa eens ea ee een ene} 3. ()
SULA ZT a Pa Nee CR eR Se Nal Seton ee Ba 331
PANO PO CUD CLKcgge sree sec ce oy cee Woe Le ee REESE Ue ae OO
Hei eran brut ete Git © Ce Set sae eee ac ae cease Sota ac ne re ace eee ar sae eae hr eee Ee 33d
Absa po len eat Ons (Oifs po| eGES ieee esces SS an ewe eae Soe ence SRE cee SB oe eee 334

INTRODUCTION

Improved methods of procedure already applied in several different
regions of the world have revealed many of the actual conditions under
which the marine animal lives. Increased knowledge of such matters
has been made possible, locally, through the Biological Survey of San
Francisco Bay made by the United States Bureau of Fisheries.

The survey was made by the U. S. S. ‘‘Albatross’’ under the
direction of a board consisting of Dr. F. B. Sumner, naturalist, Pro-
fessor Charles A. Kofoid, and Commander G. H. Burrage, U. S. N.,

300 University of California Publications in Zoology [Vou.138

succeeded by Lieutenant-Commander H. B. Soule, U. S. N., during
the years of 1912 and 1913. Much assistance has been received from
Dr. Sumner and from Professor Kofoid, who upon Dr. Sumner’s
resignation has had supervision of the work. A report by Sumner,
Louderback, Schmitt, and Johnston (1914) has been published in
which the physical conditions of the waters of San Francisco Bay are
ably presented. The data for each dredging station in that paper
have served as the basis for the discussion of the Mollusca that follows.

A portion of the general results of the studies made upon the shell-
bearing Mollusea dredged by the ‘‘ Albatross’’ in San Francisco Bay
lends itself for a separate treatment preliminary to a general dis-
cussion of the molluscan fauna as a whole, and is herein presented.
These results have to do with the so-called ‘‘quantitative’’ stations or

BF.

‘‘orange-peel bucket dredge hauls,’? which comprise forty-three out
of a much larger total number of dredgings.

The orange-peel bucket dredge had not been previously used for
biological exploration. Other devices of somewhat similar character
have been employed by Petersen (1913, p. 3) whereby a definite
amount of the bottom material could be obtained, thereby giving a
quantitative measure of the number of organisms living within a
definite area at a given locality. The orange-peel bucket dredge, de-
seribed and figured by Sumner et al. (1914, p. 7), has proved very
efficient. Regarding it, the authors state: ‘‘Its chief advantage lies
in the taking of comparatively large masses of mud from a single spot,
and particularly in the penetrating power of the apparatus which
renders possible the capture of deeply burrowing annelids, lamelli-
branches, ete.’’ Its capacity is given as 214 eubie feet. Since its
diameter is 3.16 feet, it encloses a circular area containing 7.8 square
feet.

The material collected by means of this apparatus was carefully
sorted and all of the macroscopic organisms preserved in formalin or
in aleohol. At those stations where a considerable amount of material
was obtained the following method of procedure was employed. All
of the molluscan material from such hauls was first passed over a
sieve of 5 millimeters mesh. The shells that remained in the sieve
were identified, counted, measured, and the condition of the specimens
was noted. The measurements consisted of the maximum, minimum,
and modal lengths for each species in the haul. The fine material
which passed through the sieve was thoroughly mixed and then quar-
tered after the manner of taking ore samples. A convenient sample
was then sorted and subjected to the same type of analysis as out-

1918] Packard: Quantitative Analysis of Molluscan Fauna 301

lined above. This method of procedure when large masses of finely
comminuted shells were concerned is not above eriticism, yet it seemed
to be the most practical method of treatment available.

Such a method gives excellent results for the larger mollusks and
a fair representation for the smaller ones that are abundant, but it
is sightly inaccurate for smaller shells, which are but sparsely repre-
sented in the fauna. Hence in the ease of such forms as T'urbonilla,
Odostomia, or Melanella the figures given do not represent the actual
numbers taken at a station.

The record based upon these methods shows for each species at
each dredge haul the name, the number of individuals of each species
(often approximate when these numbers were large), the conditions
of the specimens at the time of dredging, and the maximum, minimum,
and the modal lengths.

GENERAL DISTRIBUTION OF THE MOLLUSCA

PHYSICAL CHARACTERS OF SAN FRANCISCO BAY

Sumner et al. (1914, p. 22) recognized three physical and biolog-
ical divisions of San Francisco Bay. The ‘‘upper’’ portion includes
San Pablo Bay, the ‘‘middle’’ one extends from a line passing through
the points of San Pedro and San Pablo to a line drawn from the
Ferry Building to the Goat Island Light ; the third or ‘‘lower’’ division
hes south of the latter line.

The quantitative stations comprise forty-three hauls made with
the orange-peel bucket dredge between the dates of December 9, 1912,
and February 3, 1913. They were distributed from a point near the
southern extremity of San Francisco Bay to Carquinez Strait. In
the upper division of the bay twelve hauls were made at stations
D 5815 to D 5820 inclusive. Twenty hauls at stations D 5821 to D 5830
inclusive were made within the middle portion; while eleven were
made in the lower section of the bay at stations D 5831 to D 5841
inclusive. The position of these stations may be seen by referring to
plate 12.

The physical conditions at these representative stations of San
Francisco Bay are influenced largely by the surrounding topography.
The Sacramento and San Joaquin rivers and several intermittent
streams contribute considerable volumes of water to the bay. The
total discharge of these streams affects the temperature and the salinity
of the bay, besides bringing in sediment that is in part deposited
within that basin.

302 University of Califorma Publications in Zoology [Vou. 13

The depth of water at the quantitative stations ranges from 414
to 17 fathoms (8.3 to 31.3 meters). The mean tidal range for the
entire bay throughout the month is given by Sumner et al. as 4.52
feet. The actual extremes during the course of the year are much
greater, ranging from 0.4 to 7.8 at Fort Point within the Golden Gate.
The rate of the tidal currents was determined for a number of local-
ities to be about 1.4 knots per hour at a distance of a few feet below
the surface. It was estimated that the mean rate of water flow over
the entire bottom was between 0.67 and 0.75 of a knot per hour.

The mean annual temperature for the entire bay is 12°91C. The
highest recorded temperature is 20°6C and the lowest is 6°0C; the
highest of the regional means for the year was obtained in the lower
division and the lowest in the middle division of the bay. A regional
range of 12°65C occurs in the northern end of the bay, decreasing
to 4°92C at Golden Gate and rising to 11°18 at the southern end.
There is a considerable seasonal variation of temperature. During
February the temperatures are quite uniform for the entire bay,
being at that time lower than are those of the ocean outside the Golden
Gate. During the latter part of April and early May the waters at
either end of the bay are warmer than in February, whereas those of
the middle divisions are colder than they are at the earlier period.
At the next period the latter part of July a rise of temperature is
noticed, the Golden Gate remaining the coolest region of the bay.
During this period the temperature of the bay is higher than that
of the ocean off San Francisco. In the early part of October a general
decrease in the temperature is evident, and at this period, as well as
in the early part of May, the ocean temperatures are nearly the same
as those of the bay. In-late November a general uniformity of tem-
perature somewhat lower than that of the open ocean prevails through-
out the bay. The lowest temperatures of the year occur in January,
at which time the waters of the middle division are the warmest, while
those of San Pablo Bay are the coldest. The waters of the bay are
at this time and also in February colder than those of the ocean. The
annual range of the bottom temperature for the entire bay is 8°35C.
In the winter the bottom and surface temperatures are more nearly
alike than in summer.

The salinity of San Francisco Bay ranges from 3.25 to 33.27 per
mille. The mean for the entire bay for the year was estimated by
Sumner ef al. to be 27.48. The regional annual mean is less than 16
per mille in Carquinez Strait, while it reaches as high as 31 within
the Golden Gate. As might be expected, the annual range is greatest

1918] Packard: Quantitative Analysis of Molluscan Fauna 303

in San Pablo Bay, reaching a minimum at Golden Gate and increasing
but slightly toward the lower end of the bay. The minimum seasonal
mean salinity for the entire bay occurs in April and May and the
minimum in October. The bottom salinity for the entire bay is greater
than the mean surface salinity throughout the year, the difference
between the two being the greater during April and May, when the
surface salinity is the lowest of the year.

A diversified bottom is encountered, the materials ranging from
large stones within the Golden Gate to fine muds occurring charac-
teristically at the extremities of the bay.

THE Mouuuscan FAuNA OF SAN FRANCISCO BAy

The mollusean fauna obtained by means of the orange-peel bucket
dredge comprises twenty-three peleeypods and twelve gastropods.
This list represents about 43 per cent of the entire molluscan fauna
of the bay as obtained by the other types of dredges employed by
the Survey. The species taken by means of the orange-peel bucket
dredge are:

Cardium corbis (Martyn) Solen sicarius Gould

Gemma gemma, var. purpura Lea Spisula catilliformis Conrad
Hinnites giganteus Gray Tellina buttoni Dall

Macoma balthica (Linnaeus) Tellina salmonea (Carpenter)
Macoma inquinata (Deshayes) Zirfaea gabbi Tryon

Macoma nasuta (Conrad) Crepidula nivea Adams
Modiolus, cf. rectus Conrad Columbella gausapata Gould
Monia macroschisma (Deshayes) Epitonium hindsi (Carpenter)
Mya arenaria (Linnaeus) Epitonium sawinae (Dall)
Mya california (Conrad) Nassa fossata (Gould)

Mytilus edulis Linnaeus Nassa mendica (Gould)

Ostrea lurida Carpenter Nassa perpinguis Gould
Phacoides tenuiseulptus (Carpenter) |Odostomia franciscana Bartsch
Paphia staminea (Conrad) Thais lamellosa (Gemelin)
Pholas pacificus Stearns Turbonilla franciscana Bartsch
Psephdia ovalis Dall Turbonilla keepi Dall and Bartsch
Saxidomus nuttalli (Conrad) Turris, cf. incisa (Carpenter)

Schizothaerus nuttalli (Conrad)

It will be noticed that nineteen genera of pelecypods and eight of
gastropods are represented in this list.

Three of the genera are represented by two or more species:
Macoma (3), Tellina (2), Epitonium (2), Nassa (3), and Turbonilla
(2). The three species of Macoma occur quite abundantly and are
of interest in as much as they are found together within the same
dredge haul. Of these species, M. balthica was taken in 12 hauls, or
at about 27 per cent of the total number of hauls; M. inquinata in
13, or 28 per cent of the total; while the third, M. nasuta, was taken

304 University of California Publications in Zoology (Vou. 18

in 26, or 56 per cent of the total. M. balthica and M. nasuta were
taken together alive in three hauls. Shells of these two species were
associated at two additional hauls. Specimens of M. balthica and
M. inquinata were found together in three dredge hauls. Shells of
M. nasuta and M. inquinata were taken together at 11 hauls. Speci-
mens of all three species were taken at two localities. It is certain,
then, that the more distantly related species M. balthica and M. nasuta
live together within the restricted area covered by the jaws of the
orange-peel bucket dredge, and it is probable that the more closely
related species M. nasuta and M. inquinata may occur together within
the same restricted area. Attention should, however, be called to the
different distribution pattern of these three species resulting from
the plotting of all of the known local occurrences upon outline maps
of San Francisco Bay. Such a procedure shows that M. inquwnata
occurs almost exclusively in the middle division of the bay, whereas
M. balthica and M. nasuta have a much more general distribution.

The quantitative hauls are too few in number to serve as a basis
for conclusions regarding the areal distribution of any of the species.
Therefore such studies are reserved for a fuller treatment in another
paper.

The most common or the prevalent species of the quantitative hauls
may be defined as those that oceur at one-fourth or more of the hauls
(See Sumner, Osborn, Cole, and Davis, 1913, p. 69).

This list of prevalent species is as follows:

CamcliniminG Or O1gareee eee eee eee 19 hauls
Wileveoredtey lor llinl sneha ee ee 12 hauls
Mier comma) ran cy linea eae 13 hauls
IN Miey GOT Ay OTTER SUL ane eee ee ee 26 hauls
IW Dye EREQSNEN NY (open te arms oe parece eeeeaSeacenes 17 hauls
UMiry ayy Gat OTN Cia ascrescee se earn eee seees 28 hauls
Du Beal RS eco Wo BS ieee ree soe nec eecsecetecn ae 18 hauls
Ostia licen ee Lf Come ee 14 hauls
PARRY SEE), (EEN OO seer enee rep aeeemncen ee eerecceaecee eee 13 hauls
Thranist lamella siete ee eee 15 hauls

Of these, only Mya california and Macoma nasuta were taken alive
more than ten times.

These prevalent species include the most adaptable forms found
in the local fauna. Most of them are distributed quite uniformly
throughout the bay, being able to withstand easily the extremes of
the diverse environments found within these waters. The hardiness
of these species is attested also by their wide geographic distribution,
showing a marked range of environmental conditions. It is not sur-

1918] Packard: Quantitative Analysis of Molluscan Fauna 305

prising, then, that Macoma balthica and Mytilus edulis have a general
distribution within San Francisco Bay, when the same species are
able to endure the rigors of the littoral zone of the North Sea, north
Atlantic Coast, and western coast of North America. Thais lamellosa
and Zirfaea gabbi also have wide ranges on the West Coast and are
closely related to if not identical to Atlantic Coast species.

TABLE 1
COMPLETE RECORD OF THE QUANTITATIVE HAULS

ua) n n Be a a)

Ta Pare oan we 2.2 as nS ag eH HH ys

2 oO oos ° o gawd o”d os Bhs oos cog

eae 82 Be HSSEH Bey 8S ea. 882 Gee

Bon 2355 fa) esimasts) cole, fears = 250 BOF

ees Hee gs Hasna Ce 8Ss a feo sas

SS% 5 al be Fanaa FR Fa ee ah Fad
D 5815 A 2 2 2 6 0 6 2 0
D 5815 B 1 il 0 0 3 3 al 0
D5816A 0 0 0 0 0 0 0 0
D 5816 B 2 2 2 5 2 of 2 0
D5817 A 3 3 1 8 109 ialy/ 3 0
D 5817 B 3 3 3 4 15 19 2 il
D 5818 A 3 3 1 1 18 19 3 0
D 5818 B 4 4 il! 10 39 49 4 0
D 5819 A 4 3 3 10 5 15 4 0
D 5819 B 1 1 ] 3 + 7 il 0
D 5820 A 4 3 2 2 5 7 4 0
D 5820 B 1 1 0 0 9 9 1 0
D 5821 A 5 5 4. 31 iY 48 4 if
D 5821 B 11 ale 2 3 37 40 10 1
D 5822 A 3 3 1 1 224 225 3 0
D 5822 B 6 6 2 115 83 198 5 il
D 5823 A 6 6 2 17 91 108 5 1
D 5823 B 3 3 3 13 2 15 3 0
D 5824 A 3 3 2 7 24 31 3 0
D 5824 B ila] 10 3 404 2,566 2,970 8 3
D 5825 A 13 12 a 166 193 359 9 4
D 5825 B 9 8 1 1 189 190 8 1
D 5826 A 10 9 0 0 343 348 8 2
D 5826 B 10 9 2 33 126 159 8 2
D 5827 A 11 10 0 0 95 95 10 1
D 5827 B 10 9 1 2 24. 26 8 2
D 5828 A 7 7 5 458 25 483 6 1
D 5828 B 13 12 6 298 527 825 9 4
D 5829 A 12 iil 1 6 130 136 10 2
D 5829 B 0 0 0 0 0 0 0 0
D 5830 A 5 5 5 28 20 48 4 1
D 5830 B 2 1 2 17 2 19 2 0
D 5831 9 8 + 20 39 59 if 2
D 5832 8 7 0 0 69 69 Uf if
D 5833 15 12 4 259 93 352 ial 4
D 5834 8 7 2 2 80 82 6 2
D 5835 6 6 1 “2 35 37 5 1
D 5836 6 6 0 0 158 158 4 2
D 5837 0 0 0 0 0 0 0 0
D 5838 0 0 0 0 0 0 0 0
D 5839 8 8 0 0 197 197 6 2
D 5840 5 5 3 24 72 96 3 2
D 5841 idl 10 0 0 127 127 9 2

Average number per haul, 1.85 45.59 134.8 180.3

ld
(0)
(St)
\\
i=)
for)

306 University of California Publications in Zoology [Vou. 13

Table 1 shows that the average number of species of Peleeypoda
per dredge haul is 4.83 as compared with 1.06 of Gastropoda. This
preponderance of bivalves may be characteristic of inclosed waters,
for it is considerably less, judging from the qualitative hauls alone,
in the open waters just outside of the Golden Gate. The relative
abundance of the forms is shown in the fourth column, where it is
found that 45.59 living specimens were taken in the average quanti-
tative haul representing the mollusean population of 7.8 square feet
of bottom. These living specimens represent 1.85 species, showing .
that as a rule but a comparatively few forms live together at the
same time within an area less than eight square feet. The largest
number of living individuals dredged from a single locality is 458 at
station D 5828 A, which is within the middle division of the bay just
east of Angel Island (see pl. 12).

The number of dead shells, representing as they do the acecumu-
lation of a considerable period of time, have but little interest in a
faunistic study. The shells, which are often heaped into veritable
banks, may be transported by currents or various marine animals, of
which the hermit crab is the most important. At certain localities
the dredge was often completely filled with old valves of Ostrea lurida
or Mya arenaria. Oceasionally these hauls contained no living speci-
mens of the species so abundantly represented by dead shells. This
suggests a recent change in the physical conditions, at least in quiet
waters, of such a nature as to be detrimental to that species. It is
not improbable that the molluscan fauna of the bay is undergoing
modifications due to the close proximity of the cities around the bay.
The average number of dead shells per dredge haul is 134.8, which is
far under the actual number that would be obtained if several of the
above mentioned hauls of oyster shells had not been omitted.

Station D 5833 is the richest faunally of all the quantitative hauls.
This most productive haul was made 0.3 of a mile west of the Oakland
Harbor Light, within the lower division of the bay. The bottom was
characterized by Sumner et al. (1914, p. 190) as being composed of
90.5 per cent of mud and 9.4 per cent of sand; the depth is 614
fathoms; and the haul was made January 21, 1913. The complete
record of this haul is given in table 2.

1918] Packard: Quantitative Analysis of Molluscan Fauna 307

TABLE 2
A RECORD oF THE Most PRODUCTIVE QUANTITATIVE Haut, STATION D 5833
Number Total Modal
of living number of lengths
individuals individuals in mm.
(Cans alhitiman(¢ On; fos eens ese eee 0 29 24
Mirai comet ly alli aiiceeeseeees eee 128 127 15
Maicomia, amquimatar :.2.52.2.2...02 0 ft 38
Mia commalenicis iitclgesesse ese eeereee eee ee 0 20 55
IMiyae cir CN ani ay meses ee enetiae ss eee 0 1 22
IMD), (CBM O NRO cree Sher eee 2 q 11
Mis y trill rs Wee clutllas eeseecoeweeeeeee 0 2 33
Ostreamltnida, sew tease cae A 0 many ae
VE OVE), CUERVO EE a ce neree mre eee eenee 1 3 10
Schizoth@erus mutta 2 ees 0 fragm.
ZNTEAC Ae Cali Uyeeee te 2. everest eee 0 fragm.
O@repidiilea ni Car a encase eos 0 fragm. aes
HFN POE OTA TUT EGS eee 128 128 3
SEO OAL TETAS nV TAC ee cee 0 1 ze
INJAISS ae OS Sees oeses se tocees ences 0 il 22
Mhvanisiellaima ellos Bip 22a cae ese ee 0 14 13

It is of interest to note the average size of a few of the prevalent
species. Such data are tabulated below.

TABLE 3
THE AVERAGE SIZE OF THE LIVING SPECIMENS OF FIVE PREVALENT SPECIES
Maximum
length of
Average living
length of specimens
specimens obtained in
Species Number of for all hauls same hauls
specimens in mm. in mm.
Macoma nasuta 59 20 55
Cardium corbis id] 9 Vi
Mytilus edulis 4 8 17
Mya arenaria 33 25.8 80
Mya california 573 9.5 if

The averages as given above are rather low, due in part to the
relatively large numbers of very young individuals. These figures,
however, combined with those given elsewhere in this paper, make it
possible to picture the molluscan life of a typical unit area, besides
giving the approximate numbers and dimensions of the individuals
living within such an area. It is also possible to estimate roughly
the amount of organic matter represented by the mollusks, after once
having established the average number and size of the individuals
per unit area, and the ratio of the organic to that of the inorganic
matter for each species.

A picture of the mollusean life of an average unit area, such as
would be covered by the jaws of the orange-peel bucket dredge (7.8
square feet), may be obtained from a consideration of the data pre-
sented above.

308 University of California Publications in Zoology [Vou. 18

This unit area within the upper division of the bay would yield
two species, judging from the average number of species per dredge
haul for that region. Similar averages for that portion of the bay
indieate that such an area would support four living specimens and
seventeen old shells.

The same area within the middle division would yield, according
to the same line of reasoning, seven species, while the living individuals
would number 80 and the old shells 235.

A similar area within the lower division would appear to yield six
species, twenty-seven individuals and seventy-nine old shells.

The particular species represented within these three hypothetical
areas can not be determined. It is probable that such an area de-
picting the average conditions would contain some of those species
that have been listed as the prevalent species for the region considered.
The commonest simple combination of species for the upper division,
for instance, would be the two species most frequently dredged within
that region, but such a combination out of a number of other possible
combinations would rarely be obtained.

This difference in the abundance of the mollusean life within the
different regions of the bay is shown in plate 13, where the cireles of
different sizes stand for the different species and the number of circles
for the number of living individuals obtained in the average dredge
haul for the designated divisions. No attempt has been made to show
the number of old shells.

ECONOMIC CONSIDERATIONS

The mollusean fauna of San Francisco Bay and environs includes
a number of edible peleeypods. The two local species most commonly
found in the markets of the Bay region are Mya arenaria, the ‘‘soft-
shelled,’’ ‘‘mud’’ or ‘‘eastern clam,’’ and Paphia staminea, the ‘‘hard-
shell,’’? or ‘‘butter clam.’’ Other well known northern clams that
occur in the vicinity of San Francisco include: Saxidomus nuttallr,
Schizothaerus nuttalu, Mytilus edulis, Mytilus californicus, Siliqua
nuttall, Ostrea elongata, Ostrea lurida, Panope generosa, Cardiuwm
corbis, and Pholadidea penita. Two other Californian species, Tivila
crassatelloides and Chione undatella, are frequently seen in the San
Francisco markets, but they are southern species, the former, the Pismo
clam, coming principally from San Luis Obispo County.

Mya arenaria is predominantly a mud-dwelling species, and occurs

1918] Packard: Quantitative Analysis of Molluscan Fauna 309

in sheltered localities on muddy or sandy beaches. It thrives under
various conditions of temperatures and salinities. The extensive mud
flats of San Francisco Bay afford a very congenial habitat for this
exotic form, as is attested by its phenomenal increase since 1881, when
it was first reported from this region. The Survey record shows that
this species now has a general distribution within the bay, being
especially abundant on the extensive tidal flats of the upper and lower
divisions.

An excellent account of the developmental history and economic
importance of this clam may be found in the reports of the Massa-
chusetts Commissioners on Fisheries and Game. Since no detailed
work has been published regarding this particular species on our coast,
Belding’s conclusions will be assumed to apply in general to our local
forms. The following notes are drawn freely from the papers pub-
lished by the Massachusetts Commissioners on Fisheries and Game
(1916).

As is well known, this mollusk burrows deeply in the soil, lying
at a depth of from six to twelve inches. When the tide is out the
siphon is generally partly retracted, leaving an elliptical hole in the
sand, but upon the return of the tide the siphon expands and a current
of water is set up through the incurrent and excurrent tubes. The
clam once having established itself and having grown to a length of
about one and one-half inches, seldom moves, unless crowded out of
its hole by more vigorous neighbors.

Belding and Lane show that after fertilization the larva passes
through the well known stages leading up to the veliger, which is
characterized by a thin shell. This stage is reached in about twenty-
four hours after fertilization, the organism passively floating at or
near the surface of the water. A few days later it develops a pro-
dissoconch and a ciliated foot, when it settles to the bottom and at-
taches itself to a suitable support by means of a byssus. It develops
rapidly and soon acquires the burrowing habits of the adult.

In favorable localities on the Atlantic Coast a length of 30.5 milli-
meters (114 inches) is attained by the end of three and one-half
months. Belding and Lane (1916, pl. 9) claim that a clam that has
reached a length of 25 mm. at the end of six months will measure
70 mm, at 11% years, or 81.9 mm. at 214 years, or 90.7 mm. at 314
years. Such a growth expressed in terms of volume is equivalent to
an increase from 1 to 23 bushels at 114 years, 36.9 at 214 or 47 at 314
years. This clam reproduces on the Atlantic Coast at two years of age.

310 University of California Publications in Zoology (Vou. 138

On the Massachusetts coast spawning occurs from June 1 to Sep-
tember 1. There is considerable local difference in the spawning
season due to the fact that ‘‘spawning will not take place until the
water has attained a warmth suitable for the development of young
larvae’’ (Mass. Com’rs of Fisheries and Game, 1916, p. 105). It does
not necessarily follow that the spawning season of San Francisco Bay
would be the same time, for the water temperature may be suitable
for reproduction during other months of the year. This problem
should be investigated, since it has an economic as well as a scientific
significance.

It is evident that the larval stage of the clam is the most eritical
period of its life. During this stage it is defenseless, subject to the
varying conditions of surface temperature and salinity and to the
tidal currents. If the young clams drift away from a suitable bottom
they are destroyed in countless numbers, or the currents may sweep
many together so that many more become attached within a small
area than can possibly develop.

It is highly desirable to determine the localities within San Fran-
cisco Bay where the set is heavy from year to year, for such places
would supply young clams for transplanting to localities less favorably
situated as regards tidal currents.

Paphia staminea occurs commonly on sandy bottom. It, too, is a
hardy form, occurring within estuaries as well as along the sandy
beaches of the open ocean. Apparently San Francisco Bay does not
afford as suitable conditions for the development of this clam as
for the preceding species, since it was more rarely taken by the
‘* Albatross’’.

Saxidomus nuttall is not abundant within San Francisco Bay,
occurring, according to the Survey records, only within the Golden
Gate. This species is elsewhere more frequently taken from a sandy
and gravelly bottom, into which it burrows deeply. It is found along
the open ocean and within inlets within which the range of salinity
is not great. This large clam is quite abundant along Oregon and
Washington shores, where it is taken in considerable numbers. This
species, together with the following, possesses a dark epidermis around
the large muscular siphon, which detracts from the appearance of the
clam and which must be removed before it is canned.

Schizothaerus nuttalli burrows very deeply in the muddy sand of
the open ocean or bays. It was taken alive but once within San
Francisco Bay, probably because the dredge failed to sink deep enough

1918] Packard: Quantitatwe Analysis of Molluscan Fauna 311

to capture it. This species occurs most abundantly at the low water
mark and might be expected to occur sparingly along the low sandy
beaches within the middle division of the Bay. It is known as the
‘‘Washington’’ or ‘‘horse clam’’ in the Puget Sound region, where
it is now being utilized for clam nectar.

The mussels, represented by Mytilus edulis and M. californicus,
are a sea food that has not as yet received the attention it deserves.
Mytilus edulis occurs in varied environments wherever suitable sup-
ports abound. It is found attached to the rocks or piles mainly within
the intertidal zone. These small mussels are occasionally found in
local markets, where they command a good price. The large mussel,
M. californianus, is seldom found in the markets, although it is used
locally by people living near the beds. It comprised an important
article in the diet of the local Indians, as is attested by the extensive
shell mounds along the coast. Unlike the smaller mussels, this form
lives only along the shores of the open ocean, attached to the rocks
at or near low tide mark. It develops best at those places along the
rocky shore where the waves are continually breaking over them.
These mollusks can be easily harvested at extreme low tide by pulling
them off the rock or scraping them off by means of a suitable tool.
Such an industry properly regulated would add a considerable amount
of sea food to the states of California, Oregon, and Washington.

Stliqua nuttall, incorrectly named ‘‘razor clam,’’ occurs sparingly
within the middle division of San Francisco Bay. It occurs typically
within the pure sands along the open ocean. No record is available
of this species occurring in commercial quantities in the vicinity of
San Francisco, although it might be grown on almost any gently
sloping outside beach, on which but little shifting of the sand occurs.

The eastern and the native oysters occur within San Francisco
Bay. The former, Ostrea elongata, does not reproduce within these
local waters. Therefore seed oysters are brought from the Atlantic
Coast to replenish the beds depleted by harvest. The principal oyster
beds located within the lower division of the bay are now being in-
vestigated by the United States Bureau of Fisheries, and therefore
will not be further considered. The small native or ‘‘Olympia oyster,”’
Ostrea lurida, is a hardy species having a general distribution within
the bay as well as in shallow waters outside of the Golden Gate. In
places within the lower division of the bay these oyster shells literally
pave the bottom. This small oyster is now extensively used through-
out the coast.

312 University of California Publications in Zoology (Vou. 13

Panope generosa is the largest of the West Coast clams. This
northern form occurs only sparingly in the vicinity of San Francisco.
It occurs on sandy or gravelly beaches near the low tide mark, where
it burrows deeply.

Cardium corbis, the true cockle, is a hardy clam living under a
variety of conditions from those of an estuary to that of the open
ocean. It is perhaps predominantly a mud dweller, although it fre-
quently occurs on sandy or gravelly bottoms. It is one of the easiest
to procure, since it generally hes on the surface. Although this clam
has the reputation of being tough, it is suitable for, and at present
is being used, as minced clams. This species is large and lacks the
thick, dark epidermis on the siphons, making it more desirable for
mincing than similar sized or even larger clams, such as Saxidomus
nuttalli or Schizothaerus nuttalli.

The rock-boring mollusk, Pholadidea penita, oceurs quite abund-
antly in the softer rocks within the Golden Gate and along the ocean
beach. It is said to be very palatable by those living near the rocks
- in which these, incorrectly called ‘‘rock oysters,’’ live. As yet this
clam has not been considered of economic importance, although it
might well be investigated from that standpoint.

Besides these well known edible clams there are several native
forms that might well serve as food if means for their cultivation
were devised. One of these, the Macoma nasuta, occurs very abund-
antly on the muddy or sandy beaches along the bay. It is a very
small clam, about the size of the native oyster, but it has a good flavor
and is easily obtained, since it does not burrow deeply. The true

atte}

‘razor clam,’’ Solen sicarius, is reported to be excellent. It is a
deeply burrowing, sand-dwelling form that is difficult to obtain. It
probably thrives best on the sandy beaches along the ocean front.
Spisula catillifornis is represented in the Survey collections by a few
specimens obtained from the Golden Gate. It is a large but rare
clam that might possibly be successfully grown along the sandy beaches
outside San Francisco Bay. Certain species of Pecten occur very
abundantly in Puget Sound at depth of several fathoms. It is pos-
sible that the same or similar species may occur off the Golden Gate
in quantities sufficient to have an economic significance. The dredg-
ings of the ‘‘Albatross’’, however, failed to reveal any such beds at
the few outside stations.

From the above discussion it is evident that the waters of San
Francisco Bay and immediate vicinity offer suitable habitats for a

1918] Packard: Quantitative Analysis of Molluscan Fauna ae

number of edible clams. Only a few of these, however, are extensively
used for food. Unfortunately data for the production of mollusks
within California are available only for the year 1916. Even these
data are incomplete, since they include only the figures for those clams
handled by the wholesale dealers. The following figures have been
kindly furnished by the Fish and Game Commission of California.

TABLE 4
PRODUCTION OF THREE SPECIES OF MOLLUSKS FOR THE YEAR 1916

Mya arenaria

OREHOY Lever AUOTIS\C(0) IBN Soa acces eeneee eee 161,891 lbs. $8,094.55
Tomales and San Francisco Bay ...... 366,939 18,346.95
(Bodera WB aye eae esc ne es Rae 19,702 985.10

to ge oes a er ee 548,532 $27,426.60

Paphia staminea
ISO CIRCE IB Bie ence ere ts eens oases nore 1,034 Ibs. $103.40

Saxidomus nuttalli
TSU WOM OXON EI BEWA eec meee sere en cess eee 43,488 lbs. $2,609.28

San Francisco Bay yields more than 161,000 pounds of Mya
arenaria, having a value of over $8000. These figures represent
only a small part of the actual yield, as may be seen by referring to
table 4. The present yield of the bay is thought by many local clam
dealers to be much less than it was ten or more years ago. There
are, however, no figures available upon which to base an estimate of
a former yield. The wholesale price of this clam ranges from 5 to
8 cents per pound, the average being about 6 cents. Figures are
not available for the 1916 yield of Paphia staminea nor Mytilus edulis,
which are occasionally harvested within San Francisco Bay. The
hard shell clam brought in from Bodega Bay and elsewhere sells
for 9 or 10 cents wholesale. The mussels frequently sell for as
much as 121% cents retail, under normal conditions of the market.
The other clams mentioned above are rarely on the local market, and
therefore the prices are variable, depending upon the sporadic supply.
The market conditions even for the mud clams are rather unstable,
due in part to the uncertainties of harvesting, which under present
methods depend upon a favorable tide, since dredging methods are
not yet employed.

The dredging operations of the ‘‘ Albatross’’ within San Francisco
Bay have yielded data from which rough estimates of the average
numbers per acre of the different clams can be calculated.

314 University of California Publications in Zoology (Vou. 138

Mya arenaria was taken alive at 8 out of the 43 quantitative hauls,
and is represented by 32 living specimens, making an average per haul
for the entire bay of .76. This would equal approximately 1.5 bushels
per acre. This figure, however, representing the average for the bay,
is obviously of little significance. If those stations having a sandy
bottom are segregated, it is found that this type of bottom yields on
the average 1.1 living specimens per haul, or the equivalent of ap-'
proximately 2.2 bushels per acre, assuming that all were of marketable
size. Even such a yield has no economic significance, since under
favorable conditions a yield of 500 bushels per acre is not uncommon.

The quantitative dredge hauls indicate that Paphia staminea and
Saxidomus nuttallt are even less abundantly represented within the
adlittoral waters of San Francisco Bay.

The intertidal zone, having an area of approximately 17,344,000
acres, yields what clams are now obtained from the bay, since dredging
is not at present locally employed. It is probable that at least 50
per cent of this acreage is suitable for the production of Mya arenaria.
If this is so, the tidal zone of San Francisco Bay would undoubtedly
support 434 billion bushels of Mya arenaria. If markets could be
found for such an enormous amount of sea food, an industry involving
millions of dollars might be established.

This clam has been transplanted and raised experimentally on the
Atlantic Coast by the Massachusetts Commissioners on Fisheries and
Game and on an economic seale by many eastern growers. The labor
involved is slight. The planting consists of merely scattering the
young clams, obtained from localities where the set is heavy, at a rate
of fifteen to twenty per square foot. Six months or a year: later,
depending upon the size planted or the size marketed, these may be
harvested. The investment need not be great. A boat and a set of
digging tools is all that is necessary. The returns are as great as
from an acre of cultivated land, since in Massachusetts the average
yield per acre is given by Belding and Lane as $450.

Not all of the clams that are planted reach maturity. Losses may
be due to overcrowding, whereby the clam is pushed out of its hole
by its more vigorous neighbors, to shifting sand, mud or sea weeds,
or to enemies such as the starfish or certain predaceous gastropods.
The gastropods include Polinices lewisi and the exotic species Uro-
salpinx cinereus and Ilynassa obsoleta. It is to be hoped that the
eastern winkles (Lunatia heros and L. duplicata), conspicuous ene-
mies of M ya, will not be inadvertently introduced in San Francisco
Bay along with the young oysters brought from the east.

1918] Packard: Quantitative Analysis of Molluscan Fauna 315

It is probable that the tide flats of San Francisco Bay are best
adapted to Mya arenaria, although certain beaches are perhaps more
suitable to Paphia staminea or other local species not as well known
to the puble. Those adapted to the exposed ocean beach include
Siliqua nuttalli, Mytilus californianus, Solen sicarius, Saxidomus nut-
tall, Schizothaerus nuttalli, and Cardiwm corbis.

Such an industry as clam farming would not sueceed without
private control of the tide flats. This has been demonstrated along
the Atlantic Coast, where suitable acreage is either sold or leased to
the individuals. A law giving the exclusive rights to a certain pro-
portion of the tidal areas ought not to be enacted until an investi-
gation of the clam beds of the state has been made. Such an investi-
gation would include a survey of the tide lands from the standpoint
of tidal bottom, naturally productive or barren beds, their present
fauna, their position as regards tidal currents, and their position as
regards possible contamination from sewage. From such data as these
it would be possible to determine what tracts were suitable for clam
farming by the individual and what tracts should be retained as publie
property. The clamming industry would further profit by the de-
termination of those localities where the natural set is heavy. Such
localities should perhaps remain as public property in order that the
young clams might there be obtained with which to transplant the
barren areas. Other problems of interest to the clam farmer that
such a survey would solve are the period of spawning, the local rate
of growth of the different clams, and the season of maximum growth.
These would enable the clammer to determine when to transplant the
young and what sizes to use. Such an investigation might well include
the market conditions, and especially the possibilities of canning the
product. It might also be found that the demand for such sea food
could be materially increased by a well organized advertising cam-
paign.

The possibility of locating shell deposits within San Francisco Bay
which might be dredged for their lime content has led to the prepar-
ation of table 5.

Eleven out of seventy-nine tubular bottom samples examined quan-
titatively by Sumner et al. show a lime content greater than 10 per
cent. These samples were obtained from four regions, from the ex-
treme upper to the lower end of the bay. One small and economically
unimportant area occurs in Carquinez Strait, at station D 5816 A.
Although the bottom sample shows a high percentage of lime, the.

316 Unwersity of Califorma Publications in Zoology [Vou. 13

orange-peel bucket dredge revealed only a few specimens of Mya.
East of Point San Quentin the sample shows 12.26 per cent of lime
at the surface, decreasing to about 10 per cent at a depth of 70.5
centimeters. A large number of specimens of Ostrea lurida were
obtained at a near-by station. Again at stations D 5796 and D 5798
the lime content is fairly high, but at those stations the water is nine-
teen fathoms deep. The stony character of the bottom at station
D 5702, which lies within the Golden Gate, would prevent dredging
on a commercial scale.

TABLE 5

THE LIME CONTENT OF SOME OF THE TUBULAR BoTTOM SAMPLES

Nearest Depth Depth of
“Albatross” dredging Percentage of sample water in
stations station of lime in cm. fathoms
D 5816 A D 5816 A CORTON a pete ees 9
H 5301 D 5798 115.33 46-56 10
D 5796 D 5796 NGL Sy, pees ee 19
H 5129 C D 5824 10.13 50.5-70.5 2
_H 5129 D D 5824 12.26 0-20 3.5
D 5702 D 5702 AONE Mk) wasters 13
H 5306 D 5834 10.38 0-10 10
H 5309 D 5839 25.33 70-80 10
H 5310 D 5836 21.75 91-108 5
D 5783 D 5783 SG221y Le ees 2
D 5847 A D 5847 A 24.86 125-136 8.5
H 5312 D 5847 A 37.27 123.5-133.5 5

Large quantities of Ostrea lurida were dredged off the Oakland
Harbor Light at D 5832 and D 5833. They were also obtained abund-
antly farther south at station D 5835. Besides surface deposits,
Sumner et al. (1914, pl. 6) show that a layer of shells from 50 to 80
centimeters thick, extending from station H 5306 to H 5312, a distance
of about sixteen miles, lies buried in the mud to a depth of about 50
centimeters. It is this old layer that contributes to the lime content
noted in table 5 at stations D 5847 A, H 5129 C, H 5301, H 5309,
H 5310, and H 5312. At all of these stations the water is less than
ten fathoms deep, and the bottom is of a type of mud that might
easily be dredged and then washed, leaving the concentrated shell.
It is probable that the most extensive surface and subsurface deposits
occur within a radius of five miles of Hunter’s Point. A resurvey
of those waters need not be expensive and might lead to the discovery
of even greater deposits of shell than are now known.

1918] Packard: Quantitative Analysis of Molluscan Fauna 317

FACTORS GOVERNING THE DISTRIBUTION OF THE
MOLLUSCA

The previous sections of this paper dealt with the general distri-
bution of the Mollusea and with the actual numbers of individuals
living within a definite area. It now remains to investigate the dis-
tribution of the mollusks from the standpoint of their environment.
Some of these governing distribution are: the physical character of
the bottom; the salinity, temperature and depth of the water; the
distribution of the plankton which serves as food; and other biotic
factors including other organisms which may not be beneficial to the
animal under consideration.

The limited number of quantitative hauls offers less conclusive
evidence regarding the importance of some of these factors than do
the more numerous qualitative dredge hauls made during the general
survey of the bay. Petersen (1913, p. 5) has shown that the common
dredge gives an entirely different picture of the benthos from that
obtained by means of the quantitative type of dredge. The latter
brings to the surface not only the organic matter from that locality
but also the bottom materials upon which or in which the animals lived,
thus giving a more correct idea of certain factors of their environment.

TABLE 6

THE RELATIVE ABUNDANCE OF MOLLUSCAN SPECIES AND INDIVIDUALS FOR THE
DIFFERENT SECTIONS OF SAN FRANCISCO Bay

H 2 es

am o oS no]

ey ay ea oO Hy ey Eo) wy 2 w 8
° ° Seo Oo Ow q isa oo 4

ae Gel apaltsl aes Lo Z| eee caus
ge $8 233 33 ae 52 2 8a sé

re 2a mud 2 re = a =
Sey ere see g's as qa 8m 33
30 53 Bo Sc: mie ou Pa Pay On
qa ag, He slay AsH SoS AOm HOw Ty
on O23 ong ovr oA one One one O-n
ap © a0: op, OS wd S toe S tors & Nos MoS Dw
isl Sig, Bios oS aos ogo SoS sod So
yo Rd Hom Ho; oe S132) F HOn Ho: Ho
os on Os 5, o> ® ooo Oy, 22.0 O25 os
fa Feo 478 Baa Boe Roa Rae am aa

4 q

Bmtine mayan 5.9 5.4 1.8 45.4 134.8 180.3 4.8 1.06 8.6
Upper bay... Det 13.) Age) eds VO we) oss 7.8
Maddie bayiee U5 7.0 2.4 80.0 235.9 315.9 6.1 2.2 9.9
ower Waly 6.9 6.2 12 229 79.0 TOTOF V5.2 1.6 8.3

A tabulation of data derived from table 1 shows in table 6 that
the conditions within the different divisions of San Francisco Bay
are not equally favorable to mollusean life. This analysis of these
more restricted areas clearly shows that the middle division of the
bay is a much more favorable habitat for the mollusk than either of
the other two divisions. The lower section is much richer per haul
than the upper in every respect, the average number of living indi-

318 Unwersity of Califorma Publications in Zoology (Vou. 13

viduals being nearly seven times as great. These differences as brought
out in this table challenge investigation as to their causes.

There is such an inter-relation between the different factors that
determine the distribution of animals of this class that it is difficult
to determine the effect of any single one upon the molluscan life.

REATION TO DEPTH

The effect of depth upon the distribution of the Mollusea is probably
insignificant within these local waters. This conclusion is based more
largely upon a study of the distribution of the entire fauna collected
by the Survey than upon the results of this study. However, the
‘following table is presented in which the averages per haul for four
different bathymetric zones are given.

TABLE 7

THE RELATIVE ABUNDANCE OF SPECIES AND INDIVIDUALS FOR DIFFERENT
BATHYMETRIC ZONES

Average
number
of living Average number of
Depth in Number individuals species per haul
fathoms of hauls per haul Pelecypoda Gastropoda
0to 5 2 5.5 3.0 0.0
5 to 10 26 42.5 4.57 iil
10 to 15 12 31.8 DD al
15 to 20 3 152.6 5.3 6

This table suggests that the number of living individuals per
dredge haul is greater with increase of depth. A similar correspond-
ence is seen in the last column in table 6, where the greatest average
depth for the quantitative hauls occurs in the middle division of the
bay, which is there shown to be the richest faunally. This apparent
bathymetric distribution may be due to other factors which are pecu-
liar to the middle portion of the bay, in which most of the deeper hauls

were made.

RELATION TO TYPE OF BoTToM

The character of the bottom is a recognized factor in determining
the distribution of mollusks. In order to show the relative abundance
of mollusean life on different types of bottoms, the following table
has been prepared. Seven types of bottom have arbitrarily been
recognized. This classification is based upon the physical analyses of
the bottom samples, supplemented by the notes regarding the bottom

1918] Packard: Quantitative Analysis of Molluscan Fauna 319

made on shipboard at the time of dredging (see Sumner et al., 1914,
pp. 1, 111). At a number of stations the bottom was found to be
composed of two or more types of materials. These have been classi-
fied according to predominance of one type over that of the others.
For instance, a bottom which might be characterized as a muddy sand
is herein designated as sand and mud. Since objects for support are
essential to some mollusks, groups one and seven are considered in
which shells comprise a conspicuous part of the bottom material. Of
course in such a ease the presence of shell generally indicates that
conditions have long been favorable to mollusean life, therefore the
larger numbers in such a group are not necessarily entirely due to
the shell element in the composition of the bottom. The figures given
are derived from table 1, and represent the averages per haul within
the group under consideration.

TABLE 8

THE RELATIVE ABUNDANCE OF SPECIES AND INDIVIDUALS FOR THE DIFFERENT
TYPES OF BOTTOMS

ie| | 4S h
os 83 86) 2 2
FS [Pier ER Etim) (Bate
H a AB aS, =i ass ASS
34 ae & & = Bo en Soe 8&6
ie) oy "5 So SA a5 2 Sa
a2 ge Se 58 oS 525 52%
She fate S RD Z ap Za e rey Zz am BD
1. Pure mud allt 3.2 3.2 13.9 2.6 6
2. Mud and sand 14 4.0 34 41.8 3.6 4
3. Mud and shells 4. 7.0 8.7 82.5 Bed) ey
4. Sand and mud 5 9.8 8.8 33.8 7.8 2.0
5. Pure sand ft 5.0 5.0 28.0 4.0 1.0
6. Sand and gravel 4 8.25 7.5 2.0 7.0 nee
7. Sand and shells 4 als) 10.0 174.0 9.2 2.7

In interpreting these figures due allowance must be made for the
fact that the different types of bottoms are not represented by equal
numbers of hauls. When the number of living individuals is consid-
ered, it is seen that the greatest numbers were taken on bottoms char-
acterized as being composed of sand and shells; while the second
largest numbers come from bottoms of mud and shells. The pelecy-
pods are represented by the larger number of species per haul from
bottoms characterized as sand and shells, mud and shells being the
next in importanee as regards the number of species per unit area.

A study of the mollusean associations peculiar to these different
types of bottoms shows several interesting relationships. The list of
species occurring upon various types of bottoms is given below, the
asterisk indicating that the specimen was dredged alive.

320

University of California Publications in Zoology
SPECIES OCCURRING IN GRouP 1: PuRE Mup
Cardium corbis Paphia staminea
Macoma balthica*, Pholas pacificus
Macoma nasuta* Psephidia ovalis
Mva arenaria* Zirfaea gabbi
Mya california* Epitonium hindsi
Mytilus edulis* Odostomia franciscana
Ostrea lurida Turbonilla franciscana
SPECIES OCCURRING IN GROUPS 2 AND 4: MupD AND SAND
Cardium corbis* Schizothaerus nuttalli
Gemma gemma var. purpura* Solen sicarius
Macoma balthica* Tellina buttoni*
Macoma inquinata Tellina salmonea*
Macoma nasuta* Zirfaea gabbi*
Mya arenaria Crepidula niva*
Mya california* Columbella gausapata
Mytilus edulis* Nassa mendica
Ostrea lurida Nassa fossata*
Phacoides tenuisculptus* Nassa perpinguis
Pholas pacificus Thais lamellosa*
Psephidea ovalis Turbonilla franciscana
SPECIES OccURRING IN GROUP 3: MupD AND SHELLS
Cardium corbis Paphia staminea
Gemma gemma var. purpura* Psephidea ovalis
Macoma inquinata Zirfaea gabbi*
Macoma nasuta* Columbella gausapata
Mya arenaria* Epitonium hindsi?
Mya ealifornia* Nassa fossata?
Modiolus, ef. rectus Nassa mendica*
Mytilus edulis Thais lamellosa
Ostrea lurida Turbonilla keepi
SPECIES OCCURRING IN Group 5: PurRE SAND
Mytilus edulis* Tellina buttoni*
Phacoides tenuisculptus* Turbonilla franciscana*

Psephidea ovalis*

SPECIES OCCURRING IN GROUP 6: SAND AND GRAVEL

Cardium corbis Saxidomus nuttalli
Hinnites giganteus Schizothaerus nuttalli
Macoma balthica Spisula catilliformis
Macoma inquinata Tellina salmonea*
Macoma nasuta Nassa fossata

Monia macroschisma Thais Jamellosa

Mya ealifornia Zirfaea gabbi

Ostrea lurida

SPECIES OccURRING IN GROUP 7: SAND AND SHELLS

Cardium corbis Schizothaerus nuttalli
Macoma balthica Tellina salmonea
Macoma inquinata Zirfaea gabbi
Macoma nasuta Epitonium hindsi*
Mya arenaria Epitonium savinea
Mya ealifornia* Nassa perpinguis
Mytilus edulis Thais lamellosa
Ostrea lurida Turbonilla keepi

Psephidia ovalis*

[ Vou. 13

1918] Packard: Quantitative Analysis of Molluscan Fauna 321

Most of the species listed above occur in several groups of quite
dissimilar character. This would suggest that the occurrence of a
species at a certain locality does not give a true idea of its ecological
relationships. The relative abundance of a species within a dredge
haul gives a clue as to the optimum environment for that species, and
therefore may well serve as the basis for studies in faunal associations.
For this reason the average per haul for each species has been ecaleu-
lated. The group in which the highest average falls would appear
to represent that type of bottom best suited to the mollusk in question.
Such a list is given below. The number of hauls is possibly too few
to more than suggest the broad outlines of such molluscan associations.

The following species -are arranged according to their relative
abundance on the different types of bottom:

Group 1. Pure mud
Living: None
Dead: Gemma gemma var. purpura

Mya arenaria
Psephidia ovalis
Columbella gausapata
Odostomia franciscana

Group 2. Mud and sand
Living: Cardium corbis
Gemma gemma var. purpura
Crepidula nivea

Dead: Pholas pacificus
Group 3. Mud and shells
Living: Macoma nasuta

Modiolus, ef. rectus
Zirfaea gabbi

Dead: Cardium corbis
Zirfaea gabbi
Turbonilla franciseana
Turris incisus?

Group 4. Sand and mud

Living: Psephidia ovalis
Tellina buttoni
Dead: Mytilus edulis

Ostrea lurida
Nassa mendica

Group 5. Pure mud
Living: Phacoides tenuiseulptus
Turbonilla franciscana
Group 6. Sand and gravel
Living: Tellina salmonea
Dead: Hinnites giganteus

Macoma inquinata
Monia macroschisma
Saxidomus nuttalli
Tellina salmonea
Turbonilla keepi

322 University of California Publications in Zoology Vou. 138

Group 7. Sand and shells
Living: Mya californica
Macoma balthica
Epitonium hindsi
Dead: Mya california
Paphia staminea
Epitonium hindsi
Nassa fossata
Nassa perpinguis
Thais lamellosa
The above list shows several different associations of species. Of
the prevalent species, Cardium corbis, Macoma nasuta, Mya arenaria,
and Zirfaea gabbi appear to be predominantly mud-dwelling forms;
while Mya californica, Macoma balthica, M. inquinata, Ostrea lurida,
and Thais lamellosa may be classed as sand dwellers. Although these
conclusions are tentative, because of the paucity of the hauls upon
which they are based, they suggest the broad features of the different

mollusean communities.

RELATION TO SALINITY

In order to determine the influence of salinity upon mollusean
distribution, a comparison of a curve showing the number of living
mollusks for most of the quantitative stations with salinity curves for
the equivalent hydrographic stations as published by Sumner e# al.
(1914) may be made. In these curves the stations are arranged along
the horizontal axis, at distances proportionate to their relative positions
in the bay. The average number of living mollusks from the several
hauls made in the immediate vicinity of the hydrographic stations is
represented along the vertical axis of the specimen curve.

There is apparently little correspondence between the areal density
of the mollusks and the mean annual salinity. This is evident by
referring to figure B.

It appears, however, that the mean annual salinity at stations
D 5815 to D 5820 inelusive (left end of curve) is unfavorable to an
abundant mollusean life. The specimen curve as well as the following
table indicates that the average number of individuals per haul is
greatest for those stations having a mean annual salinity between 28
and 30 per mille.

TABLE 9 Average

Mean number

annual Number living

salinity Group of hauls individuals
17.16=19.37 1 8 3.1!
19.38—21.57 2 2 5.9
21.58—23.79 3 0 0.0
23.80—26.07 -f 6 9.0
26.02—28.23 5 8 12.3
28.24—30.45 6 15 82.0
30.46—32.67 u a 12.7

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9
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300

275

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225

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400

400

375

350

$25

325

300

275

275

250

225

200

175

150

; 125

100

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25

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Sess
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afv eves

S‘v zess

3‘v o2eS

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a‘v oes
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Fig. A—Specimen curve. Average number of living mollusks obtained at e

ata } tas
cp ect iy
URE | pet

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PRCA A It
hie ane ie
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1918] Packard: Quantitative Analysis of Molluscan Fauna 323

Carquinez Strait

Golden Gate

Pont SanMateo BSB AER SERRLERBRERGRENEB’SEBY

Fig. B—Mean annual salinity at each of the hydrographic stations of the
regular series. (After Sumner et al.)

324 University of California Publications in Zoology [Vou 18

It is not improbable that the annual range of salinity is even more
potent in determining the abundance of mollusks than is the mean
annual salinity. A comparison of the specimen curve with the pub-
lished curve indicating the annual range of salinity (Sumner et al.,
fig. N, p. 69) shows only a general increase in the number of mollusks
with decrease in range of salinity, for two of the highest points of the
specimen curve fall within the area of high range in salinity.

The curves showing the distribution of salinities in the bay during
April 23 to May 6 corresponds more closely with the specimen curve
than does any of the others representing the salinities at other periods
of the year.

The highest average number of mollusks per haul is found at those
stations having a mean annual salinity between 28 and 30 per mille.
If this represent the optimum salinity for the bay fauna, that portion
of the bay having a salinity most nearly that of these figures should
yield the largest number of mollusks per unit area. No portion of
the upper bay satisfies such a condition, but the middle division does
fulfil such a requirement and is also the richest faunally. The lower
bay is found to hold an intermediate position both faunally and from
the standpoint of salinity. However, since such a salinity is the rule
in the middle portion of the bay and to a lesser extent in the lower
division this apparent relationship may have but little significance.
If the optimum mean annual salinity is high, as seems reasonable, it
might be expected that the regions where the salinity is low at any
period of the year will be low in the number of mollusks per unit area.
Thus the inverse relationship shown in the curves (figures A and C)
might have been foretold. It appears, then, that minimum salinity is
one of the factors influencing the distribution of the local mollusks.
The closer correspondence between the specimen curve and the mini-
mum seasonal salinity curve than between any of the other curves
showing the salinity for the other periods of the year tends to confirm
such a statement.

RELATION TO TEMPERATURE

It is not improbable that the molluscan larvae are more susceptible
to temperature control than is the adult mollusk. An investigation
of the water temperatures during the periods of reproduction is de-
sirable from the standpoint of the oyster culture as well as from that
of pure science. Unfortunately data as to the reproductive periods
of the local species are not available. Therefore only the more con-
spicuous effects of temperature can at present be determined.

1918] Packard: Quantitative Analysis of Molluscan Fauna 325

Carquinez Strait 497

4976

497

497.

496
Golden Gate

Point San Mateo

ia Sa nO

Fig. C—Seasonal range of salinity at each station. (After Sumner e¢ al.)

326 University of California Publications in Zoology (Vou. 138

ee SS Viste fils
Carquinez Strait

0
ie
ice
€

Golden Gate

Point SanMoteo S > FB BRERA SS

Fig. D—Distribution of the salinities of the bay during the period of April
23 to May 6. This represents the minimum seasonal salinity. (Adapted from
Sumner et al.)

bE

Ea SI a a Pe i et ats

1918] Packard: Quantitative Analysis of Molluscan Fauna 327

Curves similar to those just considered suggest the importance of
the temperature factor. The mean annual temperature curve as pub-
lished by Sumner ef al. appears to have little significance when com-
pared with the specimen curve. Table 9 indicates, however, that the
larger number of living individuals per haul were obtained in regions
of relatively low annual temperatures.

TABLE 10
Average
Mean number
annual Number living
temperature Groups of hauls individuals
11.98-12.35 1 6 134.5
12.36—-12.73 2 13 41.0
12.74-13.11 3 14 42.4
13.11—13.49 4 6 Seo
13.50-13.88 5 4 0.0

It appears from figure E that those portions of the bay where the
seasonal range of temperature is high are regions in which the areal
density is relatively low. It is not certain, however, that this indicates
a causal relationship.

The correspondence between the October and July temperature
curves and that of the specimen curve indicates that more mollusks
occur within a given area where the waters are cooler during those
months. In this connection it is of interest to note that the bay fauna
includes a majority of predominantly northward ranging species.
However, it is not evident that the warm summer temperatures of
the other divisions of the bay act as a barrier to these northern forms,
for the open ocean during this period is cooler than that of the bay
and yet it has a fauna showing a southern facies.

If the temperature factor is important in determining the local
distribution of the mollusks, the greater areal density of the middle
division of the bay may be due to the low seasonal range or to the
low summer temperature.

This rather indefinite relationship between mollusean distribution
and temperature may indicate that this factor is effective only during
the reproductive periods of a particular mollusk. If these periods
do not all fall within a single season, as seems rather improbable, it is
not surprising that the influence of temperature is obscure.

RELATION TO THE AVAILABLE Foop SUPPLY
The plankton probably serves as the most important food supply

of the pelecypods, which in turn become the main supply for the
predaceous gastropods. The distribution of the plankton within San

328 University of California Publications in Zoology [Vou 13

aQ_@ O10. 20 = NSO
5 an a a a Sa SS

Corquinez Strait

Golden Gate

Paint San Mateo

> a o i | o oO Oo
° . ° e og ° 2
oO Qa Q a fed oO oO

iS
oO
Fig. E—Seasonal range of temperature at each station. (After Sumner et al.)

1918]

Packard: Quantitatwe Analysis of Molluscan Fauna 329

Carquinez Strait

Golden Gate

Point San Mat COC a: a a a eS
omt San Mateo Ue ee eh Rey Gag
Fig. F—Distribution of bay temperatures. Upper curve, July 22-31; lower
curve, October 7-12. (Adapted from Sumner et al.)

330 University of California Publications in Zoology (Vou. 138

Francisco Bay might be a factor in determining the distribution of
the mollusks if there were regions of relatively impoverished waters.
That such conditions exist is suggested in the recent studies upon the
diatoms made by Mr. E. P. Rankin. He shows that the number of
species and individuals of these plants decreases as one passes from
the middle to the upper division of the bay, and that the marine forms
are not there replaced by fresh water species. The main channel
through that arm of the bay is found to represent a region of impov-
erished water in comparison to that of the quieter and presumably
more saline water near shore.

This distribution of the diatoms is paralleled in general by that
of mollusks, as is shown by the relative number of species and indi-
viduals per haul for San Pablo Bay in comparison with the other
regions of the bay (see p. 18). However, this apparent correlation
is probably not due to the lack of food supply, for Professor Kofoid’s
studies show that the plankton of the bay is relatively rich; it is more
probably due to the salinity, which is exceedingly variable within that
region. It is thus evident, that from the data at hand no definite
conclusion regarding the relationship of the distribution of the plank-
ton to that of the mollusks can be reached.

RELATION TO THE Biotic ENVIRONMENT

The relation between the distribution of other forms of hfe and
that of the Mollusea can only vaguely be suggested. From the stand-
point of the food it seems that the distribution of the plankton when
present in quantities above the requirements of the organism has little
influence upon the occurrence of the mollusks. Until the Algae of
this region are better known it is impossible to say that certain of the
gastropods are not distributed according to the occurrence of certain
of these plants. The distribution of some of the predaceous gastropods
corresponds to that of their prey. Unfortunately no quantitative data
are available regarding the distribution of the oyster drill, Urosalpinx
cinereus, but qualitative studies show that it occurs most abundantly
upon the oyster beds. The relation of the enemies of the mollusks
and the distribution of several gastropods the shells of which are
inhabited by hermit crabs can only be ascertained by a detailed study
of the entire fauna and flora of the bay.

|

1918] Packard: Quantitative Analysis of Molluscan Fauna 331

SUMMARY

The orange-peel bucket dredge, used for the first time for purposes
of biological investigation, has been employed by U.S. 8S. ‘‘Albatross’’
at forty-three stations within San Francisco Bay.

Twenty-three species of Pelecypoda and twelve of Gastropoda were
taken by means of this dredge. The ten species that were taken at
more than one-fourth of the hauls represent the most adaptable forms
of the molluscan fauna.

The middle division of the bay is a more favorable habitat for the
Mollusea than either of the other two divisions.

Depth has little significance in determining the distribution of the
local forms.

The character of the bottom is an important distributional factor.
The most favorable bottom appears to be composed of sand and shells,
the shells serving as supports for sessile forms.

A low salt concentration or a large annual range of salinity appear
to be unfavorable to an abundant local molluscan life.

The regions in which the annual range of temperature is not great
nor the maximum high during July and October support the larger
number of mollusks per unit area. Nevertheless the significance of
the temperature factor is obscure.

Several species of edible clams live within San Francisco Bay.
Of these, Mya arenaria is most important. The present production of
the bay is probably considerably less than it was a decade ago. The
bay, under the improved methods of farming, would support an an-
nual yield of more than four billion bushels of this clam. Such an
industry should be established only after a detailed survey has been
made and many of the outstanding problems solved. Laws should
also be enacted which give private control to certain tracts suitable
to clam farming.

332 University of California Publications in Zoology [Vou. 13

APPENDIX

Table 11 is given in order to show the different groupings of the hauls that
have been made in the preparation of this paper.

For further data regarding these stations and their location within San
Francisco Bay the reader is referred to the often mentioned report by Sumner
et al. (1914).

TABLE 11

SHOWING THE DIFFERENT GROUPINGS OF THE DREDGE HAULS

5 si = si

a mn = a =

° Hq ro} w

Seta sie. (somes ae ee #2 ge #2. Be

Sar i) eo sho a SuR a) acu aee ae
D 5815 A 2, 4 1 2 D 5826 A i 2 5 2
D 5815 B 2 4 il 3 D 5826 B 7 2 5 2
D 5816 A i 3 il 2 D 5827 A 6 3 itt 4
D 5816 B al 3 i 3 D 5827 B 6 3 1 2
D 5817 A 2 4 1 2 D 5828 A 2 1 6 4
D 5817 B 2 4 1 2 D 5828 B 3 1 6 3
D 5818 A 1 2 2 2 D 5829 A 6 1 7 3
D 5818 B 2 2 2 1 D 5829 B 6 1 ai 4
D5819 A 2 2 4 2 D 5830 A 5 i 7 3
D 5819 B 2 2 4 2 D 5830 B 2 i 7 2
D 5820 A 2 3 5 3 D 5831 2 2 6 3
D 5820 B 2 3 5 2 D 5832 4 2 6 2
D 5821 A 2 2 5 2 D 5833 8 2 6 2
D 5821 B 2 2 5 2 D 5834 4 3 6 3
D 5822 A il 3 4 1 D 5835 3 4 6 2
D 5822 B 1 3 4 2 D 5836 1 5 6 2
D 5823 A 3 3 5 2 D 5837 il 5 6 2
D 5823 B 3 3 5) 3 D 5838 il 5 6 2
D 5824 A 1 3 4 3 D 5839 1 5 6 2
D 5824 B 7 3 4 2 D 5840 1 3 6 2
D 5825 A 4 2 6 2 D 5841 4 4 6 3
D 5825 B 4 2 6 3

1918] Packard: Quantitatie Analysis of Molluscan Fauna 333

LITERATURE CITED

Bewpine, D. L., and LANE, F. C.
1916. The shell fisheries of Massachusetts: their present condition and
extent, in Mass. Comm. on fisheries and game, Report upon Mollusk
Fisheries of Massachusetts, pp. 16-233.

MASSACHUSETTS COMMISSION ON FISHERIES AND GAME.
1916. Report upon Mollusk Fisheries of Massachusetts. 50th Ann. Rep.,
234 pp., pls. 1-9, several text figures.

PETERSEN, C. G.
1913. Determination of the quantity of animal life on the sea-bottom.
Ann. 1’Inst. oceanographique, 10 figs. in text.

PETERSEN, C. G.
1915. Valuation of the sea. II. Rep. Danish Biol. Station, 21, 1-44, app.
1-67, 6 pls., 3 charts.
SuMNER, F. B., OsBuRN, R. C., CoLz, L. J., and Davis, B. M.
1913. A biological survey of the waters of Woods Hole and vicinity. Bull.
U. S. Bur. Fish., 31, 1-860, 274 charts.

Sumner, F. B., LoupERBAcK, G. D., Scumirr, W. L., and JoHNsoN, G. E.
1914. A report upon the physical conditions in San Francisco Bay, based
upon the operations of the United States Fisheries Steamer
‘¢ Albatross’’, 1912-1913. Univ. Calif. Publ. Zool., 14, 1-198, pls.
1-13, 20 figs. in text.

STEARNS, R. E. C.
1881. Mya arenaria in San Francisco Bay. Am. Nat., 15, 362-366.

EXPLANATION OF PLATES

PLATE 12
Dredging stations of the ‘‘ Albatross’’ in San Francisco Bay. (After Sumner et al).

[ 334 ]

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PLATE 13

Diagram showing the relative abundance of mollusks per unit area of 7.8
square feet within the three divisions of the bay. The circles of different size
stand for the different species and the number of circles for the number of
living individuals obtained in the average dredge haul for the indicated region.
The number of old shells is not represented.

[ 336 ]

UNIV. CALIF. PUBL. ZOOL. VOL. 18

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UNIVERSITY OF CALIFORNIA PUBLICATIONS— (Continued)

Notes on the Tintinnoina. 1. On the Probable Origin of Dictyocysta tiara
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UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN
ZOOLOGY
Vol. 18, No. 14, pp. 337-396, plates 14-16 September 7, 1918

THE NHEUROMOTOR APPARATUS: OF

EUPLOTES PATELLA Peon

f &
HARRY B. YOCOM \
CONTENTS
PAGE
ATGTIsEiT © GLUT Cs ee a ac cc nee ince hee ee co 338
LXCTRINGN ALCL ETEN TNS) Ee Stee ee eae aR er a oh eee 340
AN S(GLARATG GY eetecececdceect cocci te ee oe 341
CORD ADRES, coh oS a a ee em nS ne RON RU we NEAL pia el aL Sao 341
IMG EHOOSBOtes ONE Mm AGAG OMS <2 262.02 oak oe Be ee Sere ee ee 341
SROAUIGITINS occ cece nec uetc cee a rr ree Ae ney he peienre Ae ie 344
TBS HERMA | LES TG RES) eee A Re ep ee RM I Noe a ee ee 344
Hier Aimer eae Siemens ook. 282d Js. hut Pee ee ee 348
TEKCUCO OME STE ces ee ae ee EEE SE ee eer ee pec 348
HEV ANG fo EU STi eae ek 8 Mas ca soars oe oe 349
PRO O CmeV AV CUONM CS Ges est 2c sic: 2st cates ska Sn ee ro 349
Wontrachilemcalcmol @: cc: te 5 Shoe Se eee 350
ING Gl eanemel barrie GUnT Gite ae be 2 ee a Ie 5 eo ee cua 350
BV Tey CTO TUUU CG TS ese seks he FE TN ee me ne 350
NVIETETOMUICLOUS peet ee acza cote ket hs) Se a ee Sato ae ee eee ee 351
MotOnsongans ands neuroma t Or, yp p Aue t LS esse nee eee ee eee 351
StMUICtUTeyOENCITTT 220) /i.fs01)5 18ers ee ee ee eee 352
SHHPUUGIE UD He) Lobe auaVeneal] chats Hol(e| Mi \ Geen ern Lo ee 353
SSE TAU CHUN Cle teas NE UIE A Os ONS pL] YD SATS ED LLL Se ne oe ee 354
EMIT GLO TAN Le O UT ONTO LOT, OT OAS essen eee eames ee enn eee 359
Bwidence ot neural fimie tre m4: 0s ee nei ve eee eae aie tee ee a ee Ns Reve 362
@h emi alk reac HOM oe ee eee cee eg Ue 362
IMorpliolo cacallirel artio 1s lia caesarean meee ee cee re ee Ee 362
JSST ONE CHE ORE NASI H LowNae NTI! AUIS ONE) a ee aerate ce ec meagre eal Sea Ree ee eee EE 367
IOV AIEMGy WRGONe saehi Caton biel Key eee ee Ek Ee el eee 367
Dias ONS OP UCT OTIC] CUS eeece me eee ener eee an ee ra ae EO 368
HHO RM ALO De Os Me Wil Cindy vc eee tek aa een ea ne eerie nee te Wr Oc BU 372
MonMation, Of. WW) POTIStO MUG er nets 0a Meet eee eee Et 373
Hormatvon OL new, MEULOMOtOrappPakauis) sete eee eee cee ee 8%

338 University of California Publications in Zoology [ Vou. 18

PAGE

VTS GUUS GD cae aS abe ees See octane eR eo SN eee nee 378
Pup rllane systema OG HET CMV t CS cess cee sees eee ee ne reece nee 378
INeuromiotor appara rus toi: flee let es yess esas eee seen ae nearer seen ne enn 381
Homology of neuromotor apparatus in ciliates and flagellates -................... 383

SSL 603 102 ime a te re OE eR orca re ee 386
Ttherartime cited c ie x ©. cet 8 ee 220 aeons Sess sek See eases ee ocean en Beare 388
ixpolama tions on plates = 222g: ee oe ae eae Se Sean neeans aanee eee eee 392

INTRODUCTION

In the year 1830 Ehrenberg gave the generic name Euploea to a
group of hypotrichous ciliates, but since that name was already used
for a group of butterflies he changed the name in 1831 to Euplotes,
the name in use today. The same year, 1831, he gave the name
Euplotes patella to one of the species in the genus. O. F. Miller had
deseribed this species as T'richoda in 1773 but in 1786 he changed it to
Kerona patella. Later Bory (1824) called the organism Coccudina
keromina et clausa. In the later works by Stein (1859) and Kent
(1881) the generic name remains that given by Ehrenberg (1831).

The genus Euplotes is distinguished from the other three genera
of the family Euplotidae by the presence of four marginal cirri which
are entirely isolated from one another; while in Styloplotes, the only
other genus having marginal cirri, they are arranged in two fascicles.

Besides Euplotes patella, the subject of this investigation, there
have been described for the genus Euplotes five distinct species. All
conform in a general way in shape of body, position of cirri and mem-
branelles, and shape and position of nuclei as given below for E. patella.

Euplotes harpa Stein, the largest member of the group, has a long
oval body with broad rounded anterior end. The convex dorsal sur-
face is marked by eight longitudinal dorsal ribs. The ventral surface
bears ten cirri anterior to the five anal cirri, while the anterior ventral
surface carries two blunt denticulations. The posterior margin bears
four unbranched cirri. The animal varies in length from 148-180
microns.

Euplotes longipes C. and L. is slightly smaller than EF. harpa, being
about 138 microns in length, while the ventral surface lacks the
denticulations, the whole organism presenting a smooth contour.

Euplotes charon Ehrbg. is rounded, oval, with the right side feebly
but the left side strongly convex. The anterior margin of the anterior

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 339

ventral surface is feebly denticulated. irri similar to the above
species. Length, 78-96 microns.

Euplotes worcesteri Griffin. Body oval, anterior end rounded, pos-
terior end bluntly pointed; dorsal surface much curved and usually
characterized by eight rows of sensory bristles; ventral surface flat-
tened, cytostome broad, containing forty-five to seventy membranelles
while the pharynx contains twenty to thirty membranelles. Ten cirri
anterior to the five anal cirri and from two to five marginal cirri.
Length, 72-93 microns.

Euplotes vannus O. F. M. Closely resembles E. worcesteri in
general structure. Usually the pharynx of H. vannws is shorter than
that of EH. worcestert. The most important difference is that the pos-
terior end of the macronucleus of H. vannus is recurved or itself and
slightly enlarged.

Euplotes patella has an elliptical cuirass, somewhat truncated
anteriorly with a projecting lip extending anteriorly from the cyto-
stomal field. The dorsal side is convex, while the ventral side is con-
cave, markedly so in the anterior part. A series of membranelles
extends along the left side of the wide triangular cytostome and into
the pharynx posteriorly, while anteriorly it is continued around the
anterior end dorsal to the lp, to the right anterior corner of the cyto-
stomal field. The right anterior ventral field bears nine styliform
cirri, six of which according to Kent (1881) are termed frontal cirri,
while the other three are the abdominal or ventral cirri. Five heavy
anal cirri extend backward over the posterior margin of the body from
the posterior ends of five parallel ventral grooves which begin near the
middle of the body to the right of the cytostome and extend back to
within twenty to twenty-five microns of the posterior end of the body.
There are four caudal cirri, the two to the right being fimbricated
(pl. 14, fig. 4).

The dorsal surface is marked by eleven parallel equidistant rows
of granules arranged in rosettes (pl. 14, fig. 7). The macronucleus is
roughly C-shaped with the open side of the C to the right (mac., fig.
A). The micronucleus is a small spherical body lying in an indenta-
tion on the anterior left side of the macronucleus (mic., fig. A). The
single contractile vacuole hes just anterior to the anal cirri (c. v.,
fig. A).

While Euplotes is of widespread occurrence, little literature is
found which indicates an intensive study of the animals belonging to
the genus. As has been mentioned Ehrenberg (1838) gave a brief

340 University of California Publications in Zoology [ Vou. 18

description of the genus. Stein (1859) gave several pages to a con-
sideration of the systematic position of the genus and described a few
of the different species. Likewise Kent (1881) gave a mere synoptic
account of the genus and its species. Maupas (1883) mentions seeing
some fibers extending anteriorly from the anal cirri in an unnamed
species of Hwplotes. In later works (1886-1889) he considers the
process of conjugation in Euplotes patella. Schuberg (1899) gave a
short account of the process of division of this species. Wallengren
(1901) contributes a rather full account of the formation and resorp-
tion of cirri in dividing individuals of EH. harpa and also considers
the origin of the new cytostome, while Prowazek (1903) describes
the same species and gives special reference to a system of fibers which
he finds in connection with the cirri. Griffin (1910) in two papers
describes a new species, H. worcestert, in which he gives a rather
detailed description of certain parts including a fibrillar system in
connection with the cirri, and of the division process. Other than the
above mentioned works little seems to have been written about this
group of highly specialized ciliates.

In this study of Euplotes patella it is the purpose to give a general
description of the anatomy of the animal, and a detailed description
of the system of fibers in connection with the cirri and membranelles.
This system will be described as the neuromotor apparatus and an
attempt will be made to show in what way it may be considered as
having the function of a primitive nervous system. <A description will
also be given of the division process, with special consideration of
the nuclear phenomena and the formation of the new neuromotor
apparatus in each of the daughter organisms. An attempt will also
be made to show that the neuromotor apparatus of flagellates is
homologous with that structure found in ciliates.

ACKNOWLEDGMENTS

This work was started in the winter of 1915 under the direction of
Dr. Olive Swezy, to whom I wish to express my sincere thanks for her
aid and encouragement in beginning this work. Especially do I wish
to express my gratitude to Professor C. A. Kofoid for his many helpful
criticisms and suggestions during the last year of the work.

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 341

TECHNIQUE

CULTURE

Since Euplotes can be found in almost any pool of standing water,
it is not a very difficult matter to culture the animals in the laboratory.
Euplotes patella, the organism which is the subject of this investiga-
tion, was kept in an old aquarium in the laboratory for over a year
and seemed to thrive without the supplying of any food. However,
these animals suddenly decreased in number, apparently due to the
presence of great numbers of Paramoecium bursaria, until they finally
disappeared altogether.

It was then found necessary to find some means of culturing
Euplotes. Several culture media were tried with varying degrees of
success. A weak solution of beef extract failed to give any satisfactory
results. Hay infusions such as are used for obtaining Paramoecia for
class work, seemed to be excellent for a while, as in these cultures
Euplotes associated with Stylonychia were found in abundance. The
ciliates in such cultures died after a week or more, probably because
the infusion was too strong and became too sour.

The medium most used was a 0.25 to 0.50 per cent solution of
Horlick’s Malted Milk. In these cultures the animals have been kept
for several weeks by adding water to overcome the loss by evaporation
and occasionally a small amount of the milk. Such a medium seems
best suited to supply the necessary bacteria, small flagellates and
ciliates, which constitute the food of Euplotes. Fairly good results
were also obtained by boiling dried mushrooms and diluting the in-
fusion to a low percentage.

Small beakers of 250 cubie centimeters capacity were used as con-
tainers for the cultures, and in these the Euplotes associated with
Stylonychia and Paramoecium often formed a light gray line on the
glass just beneath the surface of the water. In case a scum of mold
formed over the medium, Euplotes could always be found on the under
side of the scum. By taking a drop of water from near the top of the
culture the specimens could usually be collected in sufficient numbers
for study.

MerrTHops oF PREPARATION

For stained preparations the cover-glass method was largely em-
ployed. If Euplotes was sufficiently numerous,-drops of water could
be taken directly from the cultures and put on the cover glasses which

342 University of California Publications in Zoology [ Vou. 18

had been treated with a thin coating of albumen fixative. If the
animals were not numerous enough for this procedure they were
centrifuged at a low speed to concentrate them. The upper part of
the liquid in the tube was poured off and the few remaining drops, con-
taining many of the animals, were put on the cover glasses as described
above. The cover glasses were allowed to stand until only a thin film
of the liquid remained, and then dropped film down on the killing
fluid. After a little practice the right degree of dryness can be ascer-
tained and the animals killed with little, if any, distortion.

Several killing agents were employed, depending somewhat on the
stain which was to follow. If Mallory’s connective-tissue stain was to
be used, Zenker’s or a picro-mercuric solution made up as follows was

used :
Mier curicploicl onic @jeeeeeseees see 2 oms.
HAW Oren 2K O36 Deere Pere eee ee ne reer eee eee 1 gm.
FAN COHOIOD Gp Pees ee ee ee ae Ce 110 ce.
IGG TRS et aoe Se eee nee ee ee Se ee 20 ee.
UAC e tet aCl Cit ca cee teree ee eee ee ee 20 ee.
AO TUIVOW AO geese meee ese ete ree ee ee 50 ce.

The latter killing agent seemed to give the best results. If
haematoxylin or haematin was to be used, either Carnoy’s, Schaudinn’s,
or the picro-mercuric solution was used with varying results. All of
the killing agents except Carnoy’s were used hot. The cover glasses
to which the animals were attached were allowed to remain in the
killing fluid for from three to five minutes, then dehydrated in the
usual manner.

The same processes of staining were employed as were used by
Sharp (1913) for staining Diplodinium. The length of time of stain-
ing with the modification of Mallory’s connective-tissue stain was
altered somewhat, for it was found necessary to stain longer in the
acid fuchsin and less time in the anilin blue-oxalic acid-orange G solu-
tion. This stain was found suitable for both sections and in toto
preparations. Sometimes instead of the anilin blue-orange G-oxalic
acid mixture, a weak solution of Licht gritin in 95 per cent alcohol was
used with fairly good results. If this method is used a very few
seconds should be allowed for the Licht griin, as it takes out the red
very rapidly. Balsam was always used as a mounting medium. Some
slides stained with the above dyes have been kept for three to four
months with very little fading, but experience has proved that the
stain is not permanent.

1918] Yocum: The Neuromotor Apparatus of Ewplotes Patella 348

If haematoxylin or its oxidation product, haematin, was to be used,
the best results were obtained by killing the animals in hot Schaudinn’s
sublimate-alcohol solution. Dobell’s alcoholic haematin proved to
be the best stain, although alcoholic iron-alum haematoxylin was
quite satisfactory. These two stains were best for studying nuclear
phenomena and were also very good for parts of the neuromotor
apparatus, but, due to the necessity of destaining to a considerable
extent in order to make the preparations usable, some of the finer
fibers were completely destained and rendered indistinguishable.

If the animals were to be sectioned they were killed and dehydrated
in centrifuge tubes. From xylol they were transferred into gelatine
capsules of about three grains capacity containing paraffine. The
method followed was that employed by Metealf (1908) for Opalina.
The capsules containing paraffine were held in a rack and set in a
warming oven hot enough to melt the paraffine. As the paraffine
melted the organisms settled to the bottom of the capsule. When
cooled the gelatine could be easily soaked off and the tip of the paraffine
eylinder containing the organisms cut off and put on top of another
capsule of paraffine. This process was repeated until all of the xylol
was removed. The animals were then imbedded in paraffine in a
Lefevre watch glass. If the animals are tinged with a little eosin or
erythrosin it is much easier to handle them with only a small loss.

The sections, five to seven microns thick, were treated with either
haematoxylin or Mallory’s connective-tissue stain. Specimens killed
in the picro-mercurie solution gave the best results when treated with
the latter dye.

Intravitam staining was tried but no very satisfactory results were
obtained. Neutral red was the best dye tried and its value lay in its
property of staining certain external ectoplasmic structures, especially
the rows of granules on the dorsal side.

Silver nitrate and gold chloride were used in an attempt to demon-
strate the finer fibrillar endings, but failed to give any good results.

Some animals were studied in the living condition under a cover
glass. Others were killed by holding the slide with a drop of water
containing them over a bottle of osmic acid or chloroform. If this
was done for a very short time the animals were killed, but not dis-
torted. Such preparations were good for a study of external features
and were the only means by which the cirri could be studied in their
normal condition, for when immersed in killing fluids the cirri break
up into their component cilia.

344 University of California Publications in Z oology [ Vow. 18

STRUCTURE
EXTERNAL FEATURES

Euplotes patella is, in general shape, oval with the anterior end
slightly truncated. In a study of many hundreds of individuals, it
has been seen that the sides are normally nearly parallel, but occasion-
ally a culture will develop for a few days in which animals are found
with wide lateral winglike outgrowths, so that at the widest part the
animal is almost as wide as long. No reason ean be ascribed for this
phenomenon, since all of the cultures were kept under as nearly the
same conditions of food, temperature, concentration, etc., as possible.
The average length of E. patella is one hundred forty-five microns
while its width is about ninety microns. The average size of indi-
viduals will vary in different cultures from animals recently divided,
which are about two-thirds the average size, to animals fifteen to
twenty microns in excess of the average length.

When viewed from the dorsal side, Euplotes patella appears almost
bilaterally symmetrical, but a ventral view shows that the arrangement
of the cirri and membranelles and position of the cytostome make the
animal very asymmetrical (pl. 14, fig. 4).

The ventral side of E. patella is concave, rather strongly so anter-
iorly, but flattening out posteriorly. The dorsal side is strongly con-
vex in the middle part, but flattens out toward the edges where the
dorsal and ventral surfaces meet at an acute angle forming a sharp
edge. The dorsal surface is marked by eleven rows of rosettes of
granules (pl. 14, fig. 7). Griffin (1910) describes the rosette arrange-
ment of granules in E. worcesteri and claims that at the center of the
groups there are sensory bristles. Such sensory structures have never
been figured for Euplotes patella and I have been unable to see them
either on living or stained specimens.

As described above the ventral side of Euplotes patella is char-
acterized by the presence of cirri and membranelles arranged in a
characteristic and constant manner (pl. 14, fig. 4). These stylhform
cirri, the minute structure of which will be described later, fall into
four groups. The six frontal cirri are grouped roughly into two rows
of three each. These rows run from the right anterior corner of the
cytostome to the right edge of the animal. Slightly posterior to these
are three scattered ventral cirri. About two-thirds of the distance
from the anterior end are five large heavy anal cirri, which extend

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 345

from the posterior ends of five longitudinal grooves over the posterior
margin of the body. Along the posterior margin of the body are four
small marginal cirri. The marginal cirrus to the right is always
fimbricated, as is usually the one next to it.

The five furrows in which the anal cirri he are formed by slight
indentations of the pellicle along the line of the furrow and also a
slight uprising of the pellicle between the furrows. These ridges are
just far enough apart to permit of the insertion of the bases of the
cirri. Such a close arrangement permits the anal cirri to move in only
one plane, that parallel to the median plane of the body. Of the six
ridges bounding the five furrows, if we number from right to left, the
first, fourth, and sixth are almost twice as long as the other three, and
extend from the cirri toward the anterior right corner of the cytostome
for fifty to sixty microns. All stained specimens show a distinet granu-
lation of the posterior ten to fifteen microns of the ectoplasm of the
ridges. The granules of these areas are much smaller than those in
the other parts of the ectoplasm and when stained give the posterior
parts of the ridges a clouded appearance. Such a granulation near the
bases of the cirri indicates that a possible physiological relationship
exists betwen the cirri and adjacent ectoplasm.

Swezy (1916) pointed out that the parabasal body of certain simple
flagellates, such as Prowazekia lacertae, begins as a finely granular
chromidial body lying near the basal granule or blepharoplast of the
flagella. The function of the parabasal body is interpreted as a kinetic
reservoir or a body of reserve kinetic material. Usually this para-
basal body is connected to the blepharoplast by a rhizoplast. While
in Euplotes patella no definite threadlike connection has been found to
exist between the granular portions of the ridges and the cirri between
them, it seems probable that a relationship exists between them com-
parable to that between the parabasal body and the blepharoplast of
flagellates. If this be true the granules are to be considered as indi-
cative of reserve material which by oxidation liberates energy neces-
sary for the vigorous movements of the cirri. While not so prominent,
it is noticeable that around the bases of all of the cirri on the animal
there is an area about one micron wide which retains the haematoxylin
dyes to a greater degree than the main body of the cytoplasm.

At the anterior end of the animal is a crescent-shaped lip about
four microns wide at its middle point. In his discussion of Euplotes
patella, Stein (1859) describes the blunt anterior end of the animal as
terminating in a three-cornered lip. In no ease have I seen this lip

346 University of California Publications in Zoology [ Vou. 18

other than rounded along its entire anterior edge. It extends across
the anterior of the animal the width of the eytostomal field and in its
development it is seen that it is produced by the forward growth of
the dorsal wall of the cytostome. At each end of the lip the lateral
edges of the cytostome are continued forward and join the anterior
edge of the lip (U., fig. A). In examining the lip in either dorsal or
ventral view it is seen that it contains many small vacuoles and a strue-
ture in the form of a peculiar lattice work, which will be described
later as a tactile sense organ. When viewed in longitudinal section
the lip is seen to be wedge shaped, the heavy cuticle of the dorsal and
ventral sides joining at the margin in an acute angle in such a way
as to give the lip great rigidity. In a study of the living organism
its has not been possible to note any movement of this lip. Such a
lack of flexibility gives no indication that the lip functions either as
a locomotor organ or as a structure concerned in food getting. On
the other hand its position at the anterior end and the lattice work
structure which it contains, point to the fact that the hp may serve
as a tactile sense organ, probably in conjunction with the series of
membranelles which lie dorso-posteriorly to it.

In the anterior half of the animal is the cytostomal field, which
occupies about one-fourth of the whole ventral surface (cyt., fig. A).
This field is approximately triangular and is formed as a deep depres-
sion of the ventral side. On the left the cytostomal field is bounded
by the series of eytostomal membranelles, while on the right it is
abruptly joined by a cavity which deepens dorsally and extends under
the right ventral field for a distance of about fifteen microns or one-
sixth the width of the body at its widest part. Anteriorly the roof
of the eytostome is continuous with the projecting anterior hp. Pos-
teriorly the cytostome narrows and leads into the ciliated pharynx,
which curves rather sharply to the right and leads by a narrow tube
into the endoplasm near the median line slightly posterior to the
middle point of the body. By a twist of the series of membranelles
the posterior left half of the cytostome is ciated. The twist so turns
the membranelles that the cilia point toward the cavity of the cyto-
some, instead of at right angles to the ventral surface as they do
anteriorly. Posteriorly these membranelles extend into the pharynx,
forming the cilia on the left side of the pharynx. Similar cilia are
also found on the right hand surface of the pharynx, thus making the
anterior portion of the pharynx completely ciliated. A study of the
living animal shows that the cilia of the membranelles beat in such

1918] Yocum: The Neuwromotor Apparatus of Euplotes Patella 347

a way that the organisms used for food are carried into the funnel-
shaped pharynx and then forced into the endoplasm by the pharyngeal
cilia. Often while watching Huplotes feeding, small ciliates have
been observed struggling violently at the anterior end of the pharynx
evidently striving to swim away from the cilia which were forcing
them into the gullet. If the victims were large enough they often
escaped, but small ciliates and flagellates were usually swept into the
gullet and on into the endoplasm.

In the paragraph above, reference was made to a cavity which is
abruptly joined to the eytostome. This will be named the cytostomal
recess (cyt.r., fig. A). It extends from the pharynx diagonally for-
ward almost to the right anterior edge of the animal. Its shape is
difficult to describe but an idea of its form may be gotten from figure A.
Posteriorly this cavity lies open for nearly its whole width but
anteriorly it extends under the right ventral field for as much as
fifteen microns or about half of its width. At its anterior end it is
bent to the right and extends under the dorsal wall of the cytostomal
field. Being so directly connected with the cytostome it seemed at first
that such a recess or diverticulum must be an organ concerned in
feeding. However, after a careful study of this in both living animals
and prepared specimens, I am unable to see any evidence which would
support such a conclusion. Throughout its whole extent it is lacking
in cilia, and in no ease has it been seen to contain food or any other
substance. As to its true function there seems to be little evidence
favoring a definite conclusion. However, the following is offered as a
suggestion of its possible use. If we look at the ventral surface of the
animal, it is seen that a greater part of the cytoplasm hes to the left
of the median longitudinal axis. This hollowing out of the body on
the left would leave the right half of the body relatively heavier than
the left. If now we study the diverticulum of the cytostome in its
relation to the median longitudinal axis, we see that the greater part
of the cavity lies to the right of the line. Such a location tends to
put the center of the mass, in so far as it concerns the right and left
halves nearer the median plane, thus bringing the animal more nearly
to a bilateral balance of substance.

It is difficult to see how such a prominent structure as the diverti-
culum described above has escaped the observation of such investigators
as Ehrenberg, Stein and Kent, for it can be seen in both living and
prepared specimens. The fact that it never contains food and under-
lies a dense area of the body may account for the oversight.

348 University of Califorma Publications in Zoology [ Vou. 18

As indicated above the cytostome is bounded on the left by a series
of membranelles (cyt. mem., fig. A). These extend forward from the
pharynx to the anterior end of the animal, then around dorsal to the
anterior lip to its right hand end. In shape the whole series of mem-
branelles reminds one of the lapel and collar of a coat. For about half
of the distance along the cytostome these rows of membranelles lie flat
with the surface of the animal, but from about the middle of the series
posteriorly the whole series twists until the membranelles are at almost
right angles to the original position. In the region of the pharynx the
membranelles become shorter and in its lower part they become reduced
almost to the ciliated surface of the pharynx. In the anterior region
the membranelles make another twist. This twist 1s very much like
that which the lapel makes in going around the collar of the coat, and
the membranelles are arranged at an angle with the dorsal side of the
lip (pl. 14, fig. 7). The minute structure of the membranelles, their
method of functioning and their relation to the neuromotor apparatus
will be considered in detail in later paragraphs.

The pellicle (cu., pl. 14, fig. 5) is a rather heavy rigid struc-
ture and appears as a distinct line covering the animal completely,
thus keeping the shape of the body constant. With Mallory’s stain the
pellicle colors blue and in sections shows a distinct lne exhibiting little
differentiation in structure.

INTERNAL FEATURES
ECTOPLASM

The ectoplasm (ect., pl. 14, fig. 5) on the dorsal side of the animal
is distinctly set off from the endoplasm. It is about one micron thick
and is characterized by the presence of rather large granules, which
when viewed in sections form a layer just beneath the pellicle. With
Mallory’s stain the ectoplasm on the dorsal side takes a bluish tint.
Laterally the ectoplasm thins out until ventrally it is scarcely to be
distinguished from the pellicle, except in regions immediately around
the bases of the cirri. The ectoplasm gives rise to the cirri, mem-
branelles, basal granules and fibers in connection with them, as will be
shown in a study of the formation of new organelles. Besides these
structures the ectoplasm of the dorsal side contains the eleven rows of
rosettes of granules mentioned above. Each rosette is composed of
from eight to ten granules. In regularly fixed and stained specimens

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 349

the granules do not show but in their places are vacuole-like structures,
the granules apparently being dissolved out by the action of the
killing fluids. The rosette arrangement of the granules was best shown
in specimens stained with neutral red, killed by osmic acid fumes and
studied in the unpreserved condition. Posteriorly the rows of granules
extend to the margin of the body but anteriorly they end about ten
to fifteen microns from the anterior membranelles. There is no evi-
dence that these rosettes center around the bases of sensory bristles in
Euplotes patella as Griffin (1910) indicated for EF. worcestert.

ENDOPLASM

The endoplasm (end., pl. 14, fig. 5) occupies the central portion of
the animal and lies just beneath the ectoplasm, but ventrally it is
separated from the pellicle by only an extremely thin layer of the
ectoplasm. The endoplasm is alveolar in structure and contains large
granules, but these are not so numerous as in the ectoplasm. With
Mallory’s stain the central part of the cell stains pink. In this endo-
plasm are embedded the nuclei, food vacuoles and undigested food.
It seems that the fibers from the cirri are also in this layer, but
although this is the case it is undoubtedly true that they have arisen
in the ectoplasm and have sunk into the lower layer.

FOOD VACUOLES

The food of Euplotes consists of bacteria, small flagellates, ciliates
and diatoms, which are wafted into the pharynx by the constant action
of the membranelles. Under what might be called normal feeding con-
ditions, the ingested food lies enclosed within the area surrounded by
the macronucleus and most of it lies in the space to the right of the
eytostome and anterior to the anal cirri. At times when food is very
abundant, Euplotes feeds voraciously and as a result the whole body
becomes gorged with engulfed organisms. At such times the area in
which the food vacuoles are normally located becomes greatly enlarged
and extends forward as far as the motorium and laterally and pos-
teriorly as far as the narrowing endoplasm permits. Under these con-
ditions the structure of Eyplotes is very difficult to study as the
ingested food stains heavily and obscures the true body structures.

Several attempts have been made to determine the path of the food
vacuoles, but neither congo red, as used by Metalnikow (1912), nor

350 University of California Publications in Zoology [ Vou. 18

any other of the intravitim stains gave satisfactory results. However,
by studying animals which had become quiet under the cover glass, it
has been determined that under normal feeding conditions there is a
definite cyclosis of the cytoplasm in the area anterior to the anal cirri
and to the right of the cytostome. This movement of the cytoplasm
is In an anti-clockwise direction and may carry the food forward
almost to the region of the motorium. There seems to be no evidence
that the food of Euplotes follows the curve of the macronucleus as
Greenwood (1894) has deseribed for Carchesium. Powdered carmine
was also put in the medium but from the very few eases in which any
of it had been ingested by the Ewplotes, it would seem that Ewplotes
patella exercises some choice in food. This is in accord with Griffin
(1910) who found that FE. worcestert also did not ingest powdered
earmine. No definite attempt has been made to determine the process
of digestion in E. patella, but it would seem from the use of intravitam
stains to determine the path of the food vacuoles that it would be
more difficult to determine the digestive processes in the Hypotricha
than it is in forms like Paramoecium and Carchesium.

CONTRACTILE VACUOLE

There is but one contractile vacuole. At the time of its greatest
distention it is from twenty-five to thirty microns in diameter and lies
anterior to the two outer anal cirri and within two or three microns of
the right hand edge of the body. Its period of pulsation is relatively
slow. In normal animals which are at rest the interval is seventy to
seventy-five seconds, while in animals slowed down by the use of
nicotine the vacuoles may pulsate only once in three to four minutes.

NUCLEAR STRUCTURE

Macronucleus.—As in the case with most ciliates, Euplotes patella
is binucleate with large macronucleus and small micronucleus. The
macronucleus is rodlike and bent in the shape of a C with the two
ends on the right side of the body (mac., fig. A). The macronucleus
hes in the endoplasm and there is no indication that it is surrounded
by ectoplasm in a manner described for Diplodinium by Sharp (1913).
Due to its large size it is by far the most conspicuous structure in the
organism. Its length is about two hundred and thirty microns, and its
width, eight microns. It les about midway dorsoventrally and with

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella = 351

the exception of a curve over the pharynx is almost in one frontal
plane. In its finer structure the macronucleus is composed of approxi-
mately twenty-three thousand granules on a fine linin reticulum.
When well stained with haematoxylin the granules, which range in size
from one-fourth to one-half micron in diameter, are very distinct, well
separated from one another and almost spherical. This granular con-
dition is well brought out when stained with iron-alum haematoxylin,
but in specimens stained with Mallory’s stain the granules are not so
distinctly separated and the whole nucleus appears cloudy and rather
opaque. At the time of division a very interesting change takes place
in the macronucleus, which will be described later.

Micronucleus.—The micronucleus is a small spherical body from
two to three microns in diameter, lying on the anterior left hand side
of the animal in an indentation in the macronucleus (mic., fig. A). In
specimens well stained with haematoxylin, the micronucleus appears
as an almost homogeneous black body. When stained with Mallory’s
stain it takes the acid fuchsin quite readily and becomes a bright
orange red, while the macronucleus takes only the orange color. At
the time of division it migrates from its position occupied during the
vegetative stage to the left of the macronucleus and there undergoes
mitosis. Usually surrounding the micronucleus is an area almost
devoid of granules, probably indicating an area of rapid oxidation.
This is quite conspicuous at the time of division (pl. 15, fig. 15).

MOTOR ORGANS AND THE NEUROMOTOR APPARATUS

The term neuromotor apparatus was first used by Sharp (1913) in
his account of Diplodinium ecaudatum to designate a central mass or
motorium and fibers connecting it with the motor parts of the animal.
To this structure he attributed a neuromotor function, due to the fact
that it seemed likely that it had to do with coordinating the movements
of the membranelles and operculum and with them formed a single
integrated mechanism.

The neuromotor apparatus of Euplotes patella consists of five dis-
tinct parts, namely (1) a motorium or center of motor influences, to
use the nomenclature employed by Sharp (1913), from which the
fibers pass to the motor organs and sensory lip; (2) five heavy longi-
tudinal strands connecting the anal cirri with the inner end of the
motorium; (3) a fiber connecting the inner ends of the cytostomal
membranelles with the outer end of the motorium; (4) a lattice-work
sensory structure of the anterior lip; (5) a system of fibers, dissociated

352 University of California Publications in Zoology [ Vou. 18

from the above mentioned parts of the neuromotor apparatus, radiat-
ing from the nine cirri on the right ventral field and the four posterior
marginal cirri.

In the following description the term neuromotor apparatus will be
used in the same sense as it was used by Sharp (1913) in his account
of Diplodinium ecaudatum, that is as a primitive nervous system over
which sensory and motor impulses may pass, for coordinating the
movements of the motor parts of the animal. It may be that in such
forms as the Protozoa we have a condition too primitive to allow of
attributing a purely nervous function to this system, and that in the
evolution of the ciliates the functions of conductivity and contractility
have not become entirely separated. However, in the following discus-
sion it is our purpose to show that in Euplotes patella there is a
system which is a primitive nervous system structurally united with
the motor organs, and evidence will be brought forth to support such
a contention. Nevertheless it must be understood that in considering
this as a primitive nervous system we are considering it as a system
in which the sensory and motor functions are not entirely separated,
and that, with the exception of the structure in the anterior lip, all
fibers and granules are probably endowed with the function of trans-
mitting both sensory and motor impulses.

Structure of CirriBefore taking up a description of this neuro-
motor apparatus it is necessary to devote some space to a description
of the minute structure of the motor parts of the organism. These
motor organs are of two kinds, the cirri and membranelles, structures
quite different in appearance but essentially alike in the structure and
functioning of their elemental parts.

Little, if anything can be added to the descriptions already given
of the structure of cirri as Maier (1903) has fully taken up the struc-
ture of these organs in ciliates in general and has brought together the
principal facets concerning these organelles. Griffin (1910) has dis-
cussed the cirri of one species of Euplotes. The cirri of E. patella
conform to the general descriptions given, but do not agree in at least
one point with that for EH. worcestert (Griffin, 1910). This will be
taken up in a discussion of the basal granules of the cirri.

The cirri of Euplotes may be divided into three groups according to
their size. The largest cirri are the five anal cirri which extend from
the ends of the five longitudinal grooves posteriorly over the margin
of the body. These cirri lash back and forth in one plane. The next
smaller in size are the nine cirri anterior to the anal cirri. These lash

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 353

in a spiral manner distinctly different from the back-and-forth move-
ments of the anal cirri. The smallest cirri are the four marginal cirri,
which have a movement similar to the nine cirri described in the pre-
ceding sentence. All of these cirri of the living Euplotes are styliform
and exhibit a delicate longitudinal striation. By the action of the
killing agents or by any change in density of the medium the cirri are
broken up into hundreds of component cilia (pl. 14, fig. 3). Such
phenomena at once show that cirri are made up of a group of cilia
bound together by a thin protoplasmic membrane, very much as the
hairs of a wet camel’s hair brush are bound together by the film of the
liquid. By a change in the medium the binding substance is broken
down or dissolved and the cirri become as a dry brush with the hairs
spread apart.

In a microscopic examination of the cirri it is seen that their com-
ponent parts are imbedded in the ectoplasm just beneath the pellicle,
for at the base of each cirrus is a dense granular plate the granules of
which are the basal granules of the component cilia. Griffin (1910)
claimed that the basal granules of each cirrus of FE. worcesteri were
arranged in several parallel rows indicating that in the evolution of
the Hypotricha the cirri had arisen from several rows of cilia. This
near arrangement of the basal granules of the cirri I have been
unable to find in EF. patella, but rather have found that the granules
are arranged in an irregular fashion in the dense, almost opaque, basal
plate such as Maupas (1883) described for an unnamed species of
Euplotes ir which he saw the longitudinal fibers in connection with
the anal cirri. When stained with Mallory’s stain the granules of this
plate color red with the acid fuchsin the same as the fibers and
motorium of the neuromotor apparatus, indicating a relation at least
of a chemical sort between the two structures. Connecting with each
basal granule is the central contractile axis of one of the component
cilia of the cirrus. These granules are imbedded in the dense plate
which acts as a firm support or means of attachment for the cirrus.
This is in agreement with Maier (1903), who considers the basal plate
as the means of support for the cirrus, but it is to be remembered that
in Euplotes patella the function of support is to be attributed only to
the dense opaque protoplasmic plate in which the basal granules are
imbedded, and that the basal granules themselves are given an entirely
different function, which will be fully discussed in a later paragraph.

Structure of Membranelles—The membranelles while of a very
different shape, upon careful examination are seen to have a structure

354 University of California Publications in Zoology [ Vou. 18

very similar to that of the cirri. The minute structure of membranelles
has been fully described by Maier (1903) while Griffin (1910) de-
seribed them for Euplotes worcesteri and as far as I have been able to
determine those on Euplotes patella do not vary to any noticeable
extent from the descriptions already given for membranelles in other
ciliates. Each membranelle is composed of two parallel rows of fused
cilia which, like the component cilia of the cirri, are separated by the
action of the killing fluids. However, it is, as Griffin (1910) suggested,
very difficult to determine whether or not the cilia in the living animals
are bound together by a protoplasmic film. The basal granules of
each membranelle are arranged in two parallel rows just beneath the
surface of a furrow formed between two granular ridges of ectoplasm.
Such ridges are very distinct when seen in section (pl. 14, fig. 2) and
their granular structure is very prominent when viewed from the
ventral side. Such a granular structure probably has the same signifi-
cance as that discussed in connection with the six longitudinal ridges
associated with the anal cirri, namely a reserve supply of material
which upon oxidation furnishes energy necessary for the continuous
rapid movements of the membranelles. The granules of these ridges
are not to be confused with the basal granules of the membranelles.
The latter granules are definitely arranged in parallel rows and are
distinctly smaller than the granules of the ridges which are irregularly
arranged and are similar to the ectoplasmic granules distributed over
the whole body. When stained with acid fuchsin the basal granules
of the membranelles become bright red, as do those in the basal body
of the cirri, indicating a similarity in composition and also in function,
as will be pointed out later. Joining the inner ends of all of these rows
of granules is a granular fiber which continues around the anterior
end of the cytostome and joins the outer end of the motorium. <A
fuller description of this fiber will be given later in connection with
the neuromotor apparatus. This system of membranelles, which is
unified by the connecting fiber, waves in such a way that a current of
water is set up in the eytostome and the heavy food is carried into the
pharynx and thence on into the endoplasm.

Structure of the Neuromotor Apparatus.—We turn now to a con-
sideration of the neuromotor apparatus, a structure to which is
attributed the function of codrdinating the movements of the above
described motor organs. The first part of this to be described is a
bilobed body lying in the right anterior part of the organism, to which
certain fibers which will be described later are joined. This structure

°.

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 355

will be called the motoriwm, a term employed by Sharp (1913) in his
paper on Diplodinium ecaudatum to indicate a ‘‘common center of

”? and it is in this sense that the term will be used

motor influences,
in this paper.

The motorium as indicated above is slightly narrower at its middle
part than at the two ends, is about eight microns long and lies in a
frontal plane and obliquely to the median longitudinal axis of the
body (mot., fig. A). It was first seen as a dark body in the animals
stained with iron-alum haematin, lying close to the right anterior
corner of the triangular cytostome. In specimens which are well
destained this body is seen to be composed of very fine granules closely
grouped together, but if too dark it has the appearance of an almost
homogeneous body. When stained with Mallory’s stain the motorium
becomes bright red from the acid fuchsin and lacks the granular
appearance characteristic of specimens colored with haematin. Plate
14, figure 5 (mot.) shows that this motor mass does not have a smooth
contour, but rather that it has ragged edges with processes extending
out into the surrounding ectoplasm.

Joming to the left end of the motorium are the five large main
longitudinal fibers from the five anal cirri (a.c.f., fig. A). These
fibers converge to such an extent that they appear to join the motorium
as a single strand. By careful examination under high magnification,
these five fibers are seen to be composed of fine granules arranged so
closely together that the fibers have the appearance of granular cords.
This granular condition is evident only in specimens stained with
haematin. After such treatment the fibers are very conspicuous,
darkly stained cords lying close under the pellicle of the ventral side.
When stained with Mallory’s connective-tissue stain these fibers take
the acid fuchsin and become bright red.

A eareful study has been made to determine how these fibers join
the anal cirri, but so far the results have not been entirely satisfactory.
In a few cases the appearance has suggested that at the anterior edge
of the cirrus the fiber begins to break up into a fan shaped structure
of fine fibrils which join the basal granules of the cirrus (pl. 14, fig. 6).
This point is very difficult to determine, for as was suggested in the
description of the cirri, the basal plate of the cirrus is dense and
opaque, and if it is sufficiently destained to become transparent enough
to study, the fibers lose all of their color and become indistinguishable.
Sections have failed to lend any evidence in favor of this, and the only
evidence gained has been from a few well destained whole mounts.

356 University of California Publications in Zoology [ Vou. 18

The main longitudinal fibers were first seen and described in
Euplotes by Maupas (1883). He briefly described them as joining the
five anal cirri and extending forward, where they converge and joim
into a single thread which ended in the cytoplasm of the anterior end
of the animal. As to their function he was unwilling to make any
suggestion. Three years before this discovery by Maupas, Englemann
(1880) had described a series of fibers in connection with the marginal
cirri of Stylonychia which extended from the cirri toward the middle
of the body. To these fibers Englemann gave the undoubted function
of being nervous. Prowazek (1903) found fibers in Euplotes harpa
and Griffin (1910) found them in Euplotes worcesteri similar to those
described for Euplotes patella. Both of these authors ascribed to the

Fig. A. Euplotes patella. Ventral view showing principal organelles. Cirri
and membranelles indicated by basal granules only. X 725. Abbreviations:
a.c., anal cirri; a.c.f., anal cirri fibers; a.l., anterior lip; ant. cyt. f., anterior
eytostomal fiber; c.v., contractile vacuole; cyt., cytostome; cyt. mem., eytostomal
membranelles; cyt.7., eytostomal recess; f.c., frontal cirri; f.c.f., frontal cirri
fibers; mac., macronucleus; mb. f., membranelle fiber; m.c., marginal cirri; mic.,
micronucleus; mot., motorium; ph., pharynx; s.a.l., sensory structure of lip;
v.¢., ventral cirri.

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 357
fiber the function of contractility. Maier (1903) in commenting on the
fibers found in ciliates, suggests that they have a supporting function.
However, none of the above mentioned investigators has described
these fibers as joining to any such structure as the motorium of
Euplotes patella, neither have they given credence to the idea that the
fibers may be nervous in function.

Joining the right end of the motorium is another fiber which also
connects with certain motor parts of the animal, the membranelles,
thus forming an unbroken fibrillar complex between the heavy anal
cirri which are chiefly used in locomotion and the membranelles of
the adoral zone which function as organs of food getting, organs of
locomotion and as tactile structures. This membranelle fiber (mb. f.,
fig. A), which has the same granular structure as the motorium and
fibers to the anal cirri, extends from the motorium along the base of
the anterior lip around the anterior end of the cytostome where it
connects with the anterior cytostomal membranelles, and the lattice-
work sensory structure of the lip, along the entire left edge of the
ceytostome in connection with the lateral cytostomal membranelles. In
the pharyngeal region this fiber is indistinct and difficult to see as it is
hidden by closely massed cilia of the pharynx. When stained the
membranelle fiber shows the same staining reaction as the other parts
of the neuromotor apparatus, thus indicating that all parts of this
structure are in some way related to one another, at least to the extent
of having the same chemical composition.

In the anterior lip is another structure in connection with this
associated neuromotor apparatus, which although it has not been
heretofore described for any other species of Euplotes, is of especial
interest and significance. Along the membranelle fiber in the anterior
lip, at the points where the anterior cytostomal membranelles join the
fiber, enlargements occur from which short rodlike projections grow
out into the lip almost at right angles to the rows of basal granules of
the anterior membranelle (s.a.J., fig. A). Each of these processes is
connected with its neighbors by bifureating projections which meet it
at an angle of about 120 degrees. These second projections meet in
such a way as to form Vs with the apices pointing anteriorly. From
the apices of these Vs, short projections extend still farther forward
into the lip, forming the lattice-work structure, occupying from one-
half to two-thirds of the width of the lip. Thus the lip is provided with
a structure having a series of points extending well out toward its
anterior edge, directly connected with the fiber of the membranelles.

358 University of California Publications in Zoology [ Vou. 18

When stained this structure is colored the same as the fibers and
motorium with the acid fuchsin of the Mallory’s stain. However,
many of the specimens stained by the haematin do not show this
structure so distinctly; but this is due to the fact that the lip is so
thin that the stain is all removed before other parts of the organism
are destained sufficiently for study. Thus it is seen that the hp con-
tains a structure not only similar in its chemical reactions to the other
parts of the neuromotor apparatus, but also in its anatomical relation-
ships it is shown to be an integral part of the system, and a part which
seems likely to furnish some very important evidence indicating the
nervous function of the neuromotor apparatus, for all relations point
to the conclusion that this structure lacks both motor and _ skeletal
functions and that it functions as a tactile sense organ in connection
with the anterior cytostomal membranelle.

The last part of the neuromotor apparatus to be described is the
system of fibers in connection with the frontal, ventral and marginal
cirri. This system of fibers will be described as a dissociated part of
the neuromotor system, for in the dozens of specimens studied there
has been no indication that the fibers in connection with the frontal,
ventral and marginal cirri are in any way connected with the motorium
or any part of the neuromotor apparatus described in the preceding
paragraph.

The arrangement of the fibers of the dissociated part of the neuro-
motor apparatus differs greatly from that of the fibers in connection
with the five anal cirri. Instead of each of the frontal, ventral and
marginal cirri having a single fiber as the anal cirri, they are joined
by several much finer and shorter fibers. These fibers range in number
from four to six extending out in one direction from some of the cirri
to two or three groups of four or six, each extending out in different
directions (f.c.f., fig. A). Some of these groups in connection with
the frontal and ventral cirri may overlap each other, but in no case
has there been any indication that the fibers from one cirrus join
any other cirrus or the fibers from it. In ease of the marginal cirri
there is only one group of fibers connected with each cirrus and these
extend anteriorly and never overlap. These fibers do not join any
structure other than the cirri, but as they extend out into the cyto-
plasm they become finer until they are finally lost to view. Prowazek
(1903) described such a system of fibers for Euplotes harpa, but he
also pictures a system of fine fibers in connection with anal cirri in
addition to the five longitudinal fibers. The latter system of fibers in

———

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 359

connection with the anal cirri, I have never been able to see and feel
sure that such is not to be found in Huplotes patella. Griffin (1910)
found this dissociated system of fibers in E. worcesteri, but pictures
fewer fibers than are present in EL. patella.

Function of Neuromotor Apparatus.—In the preceding paragraphs
attention has been directed almost exclusively to a description of the
anatomical relationships of the neuromotor apparatus, which has been
divided into two parts, the associated or coordinating part and the
dissociated part joined to certain irregularly moving cirri. In the
succeeding paragraphs this neuromotor apparatus will be considered

from a functional point of view and the anatomical structures will be

considered in their relation to the activities of the organism.
In the above descriptions of the anatomy of the neuromotor appa-
ratus several suggestions have been made indicating the nervous

ce

function of the system. In fact the term ‘‘neuromotor apparatus”’
itself predicates this meaning, namely a structure in connection with
the motor parts of the organism over which neural impulses may be
conveyed. With this meaning in mind it is our purpose to show how
the different parts of this system function as a primitive nervous
system.

The motorium which has been defined as a ‘‘common center of
motor influences”’ lies in a position whereby it functions as a coordi-
nating center between the constantly moving membranelles on the one
hand and the heavy, vigorously lashing anal cirri on the other. Six
fibers, one of which connects with the cytostomal membranelles and the
sensory structure of the anterior lip and the other five heavy long
fibers from the anal cirri join the bilobed motor mass, thus permitting
of the coordination of the movements of locomotion with the move-
ments of the membranelles in food getting, as well as affording a means
of codrdinating the movements of locomotion in response to sensations
received by the anterior cytostomal membranelles and the lattice-work
structure in the anterior lip, a region which first of all comes in con-
tact with any unfavorable conditions. This function of the motorium
will be better understood when we consider the function of the strands
or fibers in connection with it.

By far the most conspicuous of these fibers are the five in connec-
tion with the anal cirri. These have been described in an earlier para-
graph as heavy granular cords connecting the motor mass anteriorly
with the large anal cirri posteriorly. In the bases of these cirri these
cords break up into a fan shaped structure of fine fibrils which join to

360 University of California Publications in Zoology [| Vou. 18

the basal granules of the cirri. Such a relationship immediately sug-
gests that these fibers are in some way associated with the movements
of the cirri. Such an association is undoubtedly true but not in the
sense that the fibers are contractile but rather that they serve as a
means by which motor impulses are transmitted from the anterior
coordinating center to the anal cirri, the chief organs of locomotion.
There is no evidence that these fibers have the function of muscular
elements, for in a study of hundreds of stained specimens I have
failed to recognize any shortening or thickening of them which would
indicate a contraction. It seems certain that if such a contraction
did occur some specimens would show it, for the killing fluids used
were such that death of the organism was undoubtedly imstantaneous
and so should have fixed some of the fibers in the contracted condition.
A study has also been made of living animals which have been slowed
down by the use of very minute quantities of a solution of nicotine.
It is possible under proper conditions of light to see the fibers in
animals whose cirri and membranelles are active. In no case has there
been seen any evidence of a contraction of the fibers, even when the
motor organs are quite active.

The criticism will probably be raised that since the fibers are
granular, it would be improbable that impulses would jump from one
granule to another. In answer to this it must be remembered that here
we are dealing with a nervous system of a very primitive sort, merely
a differentiated protoplasm. Since all protoplasm is granular to some
extent and has as one of its fundamental characteristics the property
of conductivity, it is perfectly logical to suppose that some of the
granules have become aggregated into rows in which this fundamental
characteristic of conductivity is more developed than in other parts of
the surrounding protoplasm. Then, too, the granules are so close
together that a careful study under high magnification is necessary
to bring out the granular character of the fibers. Such granules are
not lying free in space but undoubtedly are held together by a differ-
entiated intergranular protoplasm, thus forming a complete continuous
path over which impulses might pass.

Thus having established a path over which impulses may pass, it
is important to see how such impulses may be transferred to the
motor organs and how such motor organs may move when stimulated.

We have seen in the above descriptions that the fibers break up
and come in direct contact with the basal granules of the cirri. This
forms a basis for attributing to the basal granules the function -of

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 361

receiving stimuli. Such impulses received cause a contraction of the
central contractile axis of each component cilium of the cirrus, thus
causing a lashing of the whole organ. Such an idea is very much in
opposition to the view held by Maier (1903), who considers the func-
tion of the whole basal plate to be a support by which the cirrus is
held firmly in the less dense ectoplasm. The fact that the granules are
packed together into a dense plate might in itself be an argument that
the plate serves as a support for the cirrus, but even that leaves the
question of the function of the individual granules open for solution,
and it seems reasonable after considering the anatomical relationship
of the structure to attribute to the fibers and granules the function
suggested above.

A similar function is also attributed to the single fiber connecting
the motorium and membranelles. This fiber is connected to the inner
ends of the rows of basal granules of the membranelles, and although
I have been unable to discover a fibrous connection between the fiber
and the basal granules as in the case of the anal cirri, the close juxta-
position of the granules and their surrounding protoplasm forms a
continuous path for impulses which may pass over the fiber to the
membranelles. Thus there is a condition not unlke that of the cirri,
a granular fiber connecting the basal granules of the membranelle to
motorium, the fiber to serve as a path for impulses from the motorium,
while the basal granules are that part of the motor organelle especially
adapted to receiving them.

Connecting with this membranelle fiber is the lattice-work struc-
ture of the anterior lip. As suggested in an earlier paragraph all
evidence is lacking to suggest that this structure serves as a skeletal or
muscular element. In fact its position with its many points extending
out into the lip and its structural connection with the membranelles
and the membranelle fiber strongly suggest a sensory function for
this peculiar structure. We must undoubtedly attribute some sensory
function to the anterior cytostomal membranelles, but observations
show that these organs are active agents in swimming and are probably
to be considered as having no greater sensory function than the mem-
branelles along the left side of the cytostome. It is evident from
watching the animals swimming about that they are very sensitive at
the anterior end, and if the membranelles are considered as locomotor
rather than sensory organs then the organ which is most closely asso-
ciated with them is the lattice-like structure of the hp, which with its
points extending well toward the anterior edge of the lip, is in position

362 University of California Publications in Zoology [ VoL. 18

to receive stimuli from external sources and to convey impulses to the
motor organs. There is thus established a fibrillar connection between
the sensory structure of the ip and the motor parts of the organism.
Such a relationship strongly suggests the idea brought out in an
earlier paragraph, namely, that we are dealing here with a system of
such a primitive type that the motor and sensory functions are not
separated but that they are both in the same fibers.

Thus it is seen that Euplotes patella possesses a structure well
adapted for relating the organism to its environment, and to coordinate
the movements of feeding and locomotion in such a way as to bring
the animal under the most suitable circumstances for its existence.

Evidence of Neural Function.—The question at once arises, why
attribute a nervous function to this system? Evidence favoring such
a conclusion comes from a study of both living and stained specimens,
so that it is not necessary to depend wholly upon one source of evidence
as a basis for such ideas.

1. Chemical Reactions.—The first point favoring the idea that the
neuromotor apparatus is of a truly nervous character comes from
animals stained with Mallory’s connective-tissue stain. In animals
treated with this combination of dyes, different organs take different
colors. It is characteristic in metazoan tissues treated by these colors
for different tissues to stain differently, as for example nerve fibers
have an affinity for acid fuchsin and are thus dyed red while nuclei
stain orange red, and cytoplasm in general becomes ght pink. Such
a differential stain may be used to give a clue to the function of
organelles in some of the more complex of the so-called unicellular
organisms. At least we may assume that structures having a similar
staining reaction have the same or related chemical composition and
in these so-called simple organisms probably the same general function.

This is one of the reasons for basing our conclusion that the struc-
tures deseribed as comprising a neuromotor apparatus are probably
nervous in their function. All of the fibers, granules and motorium
stain bright red when treated with Mallory’s stain, while the other
structures take other colors. The only other organ which constantly
stains with acid fuchsin is the micronucleus, but in this the color is
not the same as in the fibers but has more of the orange G mixed with
the red.

2. Morphological relationships.— Were we to base our notion of the
function of the neuromotor apparatus solely on the staining reactions
our conclusions might well be subject to severe criticism. However

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 363

there are other factors which seem far more significant. Chief among
these is the intimate relation between the neuromotor apparatus and
the motor parts of the animal concerned in locomotion and feeding.
Without exception all of the above described structures, that is the
fibers, motorium and granules, are more or less closely associated and
connected with every part of the animal which has to do with its
locomotion or food getting, or both.

The largest cirri and those capable of the most powerful stroke are
the anal cirri, and as we have seen they are connected by heavy fibers
to a mass which has been termed the motorium, or as has been sug-
gested, a coordinating center. These large cirri move in only one plane
but are the chief organs of locomotion while the other cirri move in a
whirling motion and are almost constantly lashing about. The fiber
in connection with the eytostomal membranelles is also connected with
the motorium. This likewise favors the idea that the motorium is a
coordinating center and that the fibers connected with it are of nervous
character, for the phenomenon of food getting must in these forms be
closely associated with the phenomenon of locomotion, since the food
is largely made up of free, rapid-swimming organisms and not the
minute forms that serve as food for the sessile ciliates such as
Vorticella.

In studying Euplotes patella that have been treated with very weak
solutions of certain chemicals such as neutral red, methylene blue and
especially nicotine, it has been noticed that the anal cirri and the
eytostomal membranelles are the last to cease moving. The other cirri
become quiet but the anal cirri and membranelles have been seen to
move even after the cytoplasm has begun to break up. Such phenomena
favor very strongly the idea that the motorium serves as a coordinating
center between the anal cirri and cytostomal membranelles. However,
other observations on living animals give even stronger evidence in
favor of the neural function. It has also been noticed in specimens
that have been subjected to a very weak solution of nicotine that the
frontal, ventral and marginal cirri continue moving even after the
animal has ceased to swim about. The membranelles also move but
more slowly than in normal animals. Occasionally one or more of the
anal cirri may be seen to make a feeble movement not sufficiently
strong to cause the animal to move. However as the animal revives
from the effects of the narcotic and begins to swim about by vigorous
kicks of the anal cirri, a decided increase in the rate of movement of
the membranelles may be noticed. Such an increase continues as long

364 University of Califorma Publications in Zoology [ VoL. 18

as the anal cirri continue to move, but as they cease to lash back and
forth and the animal comes to rest, the movements of the membranelles
also slow down. No very decided change has been seen in the rate of
movement of the frontal, ventral or marginal cirri. The fact that as
the anal cirri move there is increased activity on the part of the
membranelles, seems to be very significant, and this coupled with the
fact that there is a definite anatomical connection between these motor
parts, leads us to the conclusion that there is a codrdination between
the two structures which takes place by means of the motorium and
connecting fibers.

Observations also serve as a basis for attributing to the lattice-work
structure of the hp the function of being a tactile sense organ. It has
been seen that animals when swimming are very sensitive at the
anterior end. Their sudden reversal of movements when striking an
obstacle shows that they have some means of receiving tactile stimuli.
The facts that this structure in the lip is so closely connected with the
organ of locomotion as well as the organs of food getting, and that it
has the same chemical affinities as the other parts, show that it is a
part of the neuromotor system. This structural relationship and the
behavior of the organism seem to prove that this structure of the lip
serves not as an organ of motility or support, but as an organ of touch
for the anterior end of the body.

As shown above, the whirling irregular movements of the frontal,
ventral and marginal cirri are in no way coordinated with the regular
rhythmical movements of the membranelles or with the backward kick
of the cirri. Such a lack of codrdination may be accounted for when
it is remembered that there are thirteen cirri possessing what we have
called a dissociated neuromotor apparatus which is not connected with
the motorium or cdordinating center.

It is probable that we are dealing here with a portion of the neuro-
motor system, which in the evolution of the organism is not yet con-
nected with the other central codrdinating parts. Here the cytoplasm
has become differentiated to a certain point—far enough for the fine
fibrils to have formed, but not far enough for the fibrils to have become
condensed into a single strand like the ones connected with the anal
cirri. Such a system of dissociated fibers might serve to receive and
convey to the cirri general impulses such as are undoubtedly carried
over the whole cytoplasm of the organism. Such impulses stimulate
the cirri to move but not in such a codrdinated manner as is char-
acteristic of the other motor parts of the animal.

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 365

As was suggested in an early paragraph of the description of the
neuromotor apparatus, we are probably dealing with a nervous system
of a very primitive sort, a nervous system formed merely by a differ-
entiation of protoplasm having the fundamental characteristic of con-
ductivity. Since contractility is just as fundamental a property of
protoplasm as is conductivity it may be that even in this differentiated
portion the two are not entirely separated and that the fibers may act
as muscular elements to a slight extent. However, much as we have
had this idea in mind in attacking this problem, we have so far failed
to find the least evidence that the intra-cytoplasmic fibers of the neuro-
motor apparatus as found in Euplotes patella in any way serve as con-
tractile structures.

It may be said by some critics that the fibers in Huplotes described
above as a neuromotor apparatus are comparable to the so-called
myonemes of other ciliates and that their function must be that of
contractility. It seems that sufficient proof has been advanced to do
away with such criticism; it might be suggested here that instead of
the neuromotor apparatus being comparable to the myonemes of ciliates
and the movement of cilia being due to the contraction of the fibers,
the myonemes may be found by further investigation to be comparable
to this neuromotor system and that the movement of cilia is due to the
contractility of the central axis of each cilium, while the so-called
myonemes may be found to be a fiber of a coordinating neuromotor
apparatus, or it may be found to have both a neural and a muscular
function combined at least in some of the less complex ciliates.

The motorium in Euplotes patella is quite comparable with that
found in Diplodinium and the argument advanced against its having
a motor function in the latter animal seems well set forth by Dr. Sharp:

The shape, size, position, and absence of direct connections with surrounding
structures make the possibility of the motorium functioning as an organ either
of contraction or of support seem highly improbable. For in order to function
as an organ of contraction it would necessarily need to have as its attachments
on the one hand structures which are fixed, and on the other structures which
are movable, or it would need to be located between two structures both of
which were to be moved. This, however, is not the case, for the motorium

seems to have no direct connections with the fixed structures of the body ....
(1913, p. 86).

The motorium (mot., pl. 14, fig. 5) of Huplotes lies free in the eyto-
plasm with no evident connection between it and the pellicle, which
is the only firm structure of the body. We can add nothing to the
argument quoted from Sharp for Diplodinium to increase its force as

366 University of California Publications in Zoology [ Vou. 18

an argument for Euplotes patella. It seems quite as adequate for the
latter as it did for the organism for which it was written.

Neither can we see any way in which this neuromotor apparatus
may serve as a supporting structure. Its shape is not such that it
would be advantageous as a skeletal organelle; neither is it large
enough to serve as a firm attachment for contractile fibers. The
pellicle, which is quite thick, can serve as a means of support. In fact
the pellicle is of such a character that the shape of the body is kept
constant and permits of little or no bending.

The only part of the whole neuromotor apparatus which might in
any way serve as a skeletal organ is the lattice-work structure in the
anterior lip. However, it seems that sufficient evidence has been
advanced to show that it serves as a sensory organelle, whose function
it is to receive sensations caused by stimuli at the anterior end. Then
too, the lip is so thin that no skeletal structure is needed aside from
the rigid pellicle on both dorsal and ventral sides.

In his deseription of the neuromotor apparatus of Diplodinium
ecaudatum Sharp (1913) describes a number of fibers in connection
with the neuromotor apparatus which extend into the cytoplasm and
end near the micronucleus. From the work on the soil amoeba,
Naegleria gruberi (Wilson, 1916), and certain of the flagellates, such as
Polymastix (Swezy, 1916), Trichomonas (Kofoid and Swezy, 1915).
and Giardia (Kofoid and Christiansen, 1915), it has been shown that
the motor organs are connected with the nucleus by a rhizoplast and
are probably controlled by it. This relationship will be more fully
discussed in later paragraphs in which a comparison of the neuro-
motor apparatus of flagellates and ciliates is taken up. However, this
relation of the motor organs and nucleus in flagellates and the indi-
eation of such a relationship in Diplodinium suggests a possible struc-
tural relationship in other forms. In Euplotes patella there is no
indication of a connection between the neuromotor apparatus and either
the micronucleus or macronucleus. The motorium is on the opposite
side of the animal from the micronucleus. At division the micro-
nucleus migrates from its position during the vegetative stage to the
left of the macronucleus, where it undergoes mitosis. The two halves
separate, one remaining in the anterior end to become the micro-
nucleus of the anterior daughter, while the other migrates posteriorly
to become the micronucleus of the posterior daughter. While this is
occurring there is no indication of any change in position of any part
of the neuromotor apparatus. It would seem that if the neuromotor

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 367

apparatus were connected with the nucleus, changes should be noted
in it comparable with those occurring in the nucleus. A consideration
of the behavior of the neuromotor apparatus during cell division will
be taken up later.

BEHAVIOR OF ORGANS AT BINARY FISSION
DIVISION OF THE MICRONUCLEUS

The first indication of division in the micronucleus is its migration
from its position in the indentation of the macronucleus to the left
side of the macronucleus, where it enlarges (pl. 15, fig. 14) to two or
three times its original size. In the resting condition and prophase it
is very difficult to make out the arrangement of the chromatin in the
micronucleus due to its compact condition. Occasionally there is
some indication of a diffuse spireme formation. Griffin (1910) de-
scribes a spireme formation in EF. worcesteri and in all probability
such a change occurs in the nucleus of E. patella. After enlarging
somewhat the nucleus assumes a spindle form with the chromatin
broken into chromosomes which lie lengthwise on the spindle. The
number of these chromatin bodies is small, and while I have not been
able to make many conclusively satisfactory counts, it seems that there
are six (pl. 15, fig. 15). This corresponds to the number given by
Griffin for EH. worcestert. As transverse division is completed the
daughter chromosomes become massed at the ends of the elongated
spindle. The two poles move apart but remain connected for a time
by a deeply staining thread. In such a condition it is almost impos-
sible to make out any definite nuclear structure, for the whole drawn-
out nucleus appears almost homogeneous and in haematoxylin prepara-
tions a dense black. Later the connected thread breaks (pl. 15, fig. 17)
and all indications of it are lost. It is probably drawn up into the
nucleus, for each daughter micronucleus becomes rounded and is to all
appearances like the original micronucleus, but only about two-thirds
the original diameter of the parent nucleus.

The process of division of the micronucleus is evidently quite rapid,
for many cases of the beginning of migration can be found as well as
of the daughter nuclei, but the cases of actual division are very rarely
found.

The mitotic changes occurring in the micronucleus are accompanied
by changes in the macronucleus. The reconstruction of this organelle
will be deseribed next.

368 University of California Publications in Zoology [ Vou. 18

DIVISION OF THE MACRONUCLEUS

About the time that the micronucleus begins to migrate from its
position in the indentation of the macronucleus, there appears at each
end of the macronucleus a very conspicuous band. Each band is made
up of two distinct areas: one a very heavily stained part, and joining
to it on the side toward the end of the nucleus a non-staining portion,
apparently almost, if not entirely free from chromatic material (pl.
15, fig. 14). As stated above the dark portion of the band stains very
heavily and if overstained appears almost homogeneous. However, by
careful destaining it can be shown that this area is in reality one in
which the chromatin granules are very closely packed together. This
part of the band was first noticed by Stein (1859) in E. patella, but
from then on until Griffin (1910) deseribed it for E. worcesteri no
one seens to have noticed it. To this band Griffin (1910) gave the
name ‘‘solution plane’’ and suggested that in this region the chromatin
was in solution in the karyolymph. Immediately distal to this solution
plane is another band which is called by Griffin (1910) the ‘‘recon-

?

struction plane.’’ This part of the nucleus takes no stain except for
a few granules (pl. 15, fig. 16), the whole area appearing as though
the chromatin material had been removed, leaving only the linin net-
work of the nucleus. Taken together Griffin calls the two areas the
‘‘reconstruction band.’’

The two planes are sometimes about the same thickness but in the
majority of cases the solution plane is thinner, being about two microns
wide while the reconstruction plane is about three microns wide. The
fine fibrils which run through the reconstruction plane seem to be
connected to the ragged edge of the solution plane on one side and to
the chromatin granules of the reorganized area on the other. The
granules which are to be seen in the light area indicate that a re-
organization process is going on in the compact area, and that the
reformed granules pass along the fibers of the light area to the distal
part of the nucleus, which is made up of the reconstructed granules.
These two parts of the nucleus, the original nucleus and the two distal
parts, are sometimes similar, that is the granules are about the same
size and have a similar staining reaction, but-in other specimens the
granules in the reorganized area are larger and stain more heavily
than those in the original unchanged part of the nucleus.

The two reorganization bands migrate toward each other until they
meet at the middle of the nucleus. During about half of the period

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 369

of migration of the bands there is little change in the size of the
nucleus (pl. 15, fig. 14). However, as the two bands approach each
other the whole nucleus shortens and thickens, the granules are
crowded close together and it seems that there is more or less of a
coalescence of the granular elements, for many granules can be seen
which are equal in size to three, or four or more of the original
granules. As the bands come nearer together the nucleus becomes
more contracted until the greatest period of concentration occurs at
about the time that the body begins to constrict (pl. 16, fig. 18). At
the period of greatest concentration the granular structure of the
nucleus has become almost obliterated, and the nucleus has an almost
homogeneous structure. In specimens which are very much destained
the contracted nucleus is seen to be made up of large chromatin masses
very much crowded together.

As the body begins to constrict the nucleus again elongates. The
granules are very irregular in size and shape, and appear as though
they were being pulled by considerable force, for many of the large
granules are much elongated and look something like chromosomes
(pl. 16, fig. 19). However, there is no evidence that chromosomes do
form, for the macronucleus divides amitotically with no indication
that the chromatin granules are divided in any way comparable to the
division of chromosomes. As the constriction of the animal continues
the macronucleus elongates and becomes narrow in the region of the
constriction of the body until finally it is completely severed (pl. 16,
fie 21):

While it is impossible to distinguish the position of the two fused
reorganization bands at the time of greatest contraction, it seems that
their plane of fusion must be the plane of division of the macronucleus,
for the nucleus divides into two approximately equal parts.

Before the nucleus has completely divided, it has begun to bend in
what is to be the anterior daughter organism and also just posterior
to the plane of constriction. When divided the nuclei are each shaped
somewhat as an inverted letter L, with the base of the letter extending
across the anterior end of the animal and the long arm along the left
side (pl. 16, fig. 21). Associated with the daughter macronuclei are
the daughter micronuclei, which lie near the angle of the L.

Such a contraction of the chromatin material at once reminds one
of the contraction stages occurring in metazoan germ cells. The first
contraction, that occurring in the reorganization bands, is a progressive
contraction, and begins at the end of the nucleus and migrates toward

370 University of California Publications in Zoology [ Vou. 18

the middle of that organelle. A careful study has shown that the
so-called solution band in E. patella at least is not homogeneous, but
that it is granular, indicating a very compact massing of the granules
at one region and a subsequent passing of them out over the lght
staining reconstruction plane to the more diffusely arranged reorgan-
ized parts of the macronucleus. This contraction reminds one of the
synizesis which was designated by McClung (1905) as occurring in
orthopteran germ cells. However, we are not willing to admit that
this contraction in Euplotes is an artifact (Whiting 1917, and Hance,
1917), as some of McClung’s students have recently suggested for
orthopteran cells, since it appears after use of all the killing fluids
and stains employed by us.

The second contraction is that of the nucleus as a whole, which
follows the first contraction and immediately precedes the constriction
of the organism. This was described in an earlier paragraph and its
significance will be discussed later.

It seems very doubtful that the term solution plane, as used by
Griffin (1910) is in any way the proper term to use in denoting the
condensed band appearing across the nucleus. As was pointed out in
the paragraph above, this band is not homogeneous but granular. True,
a change does take place and the chromatin grains coming out of this
band may not be the same as those going into it, but observational
evidence fails to show that the chromatin is in solution, but rather to
show that the granules in that region have become crowded into a
compact mass and that they pass over the reorganization plane not as
precipitated granules, but as granules which have undergone some sort
of physical and possibly chemical reorganization.

For these macronuclear phenomena we would propose the terms
‘‘eontraction phase’’ to indicate the contraction of the nucleus as a
whole, while in place of the terms reconstruction bands as given by
Griffin (1910) we would suggest ‘‘reorganization bands,’’ indicating
a purely physical reorganization of the nuclear material through a
contraction of the chromatin, rather than a solution of the chromatin
in the karyolymph.

What reason can be assigned to such a behavior of the macro-
nucleus? This is a difficult question to answer satisfactorily. Such a
phenomenon is not peculiar to Ewplotes but has been observed in other
forms. Calkins (1911) describes a distinct reorganization of the
macronucleus at the time of division in Uronychia. Here the changes
are not quite similar to those occurring in Euplotes, but the reorgan-

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 371

ization of the nucleus is characterized by the coalescence of its several
parts into one body which divides amitotically. Anigstein (1913)
finds a nuclear change in Strombidium testaceum quite comparable to
that in Euplotes. In each arm of the macronucleus a diagonal un-
colored area appeared. This begins at the middle and works out
toward the end, leaving the granules in the central part much larger
than those in the undisturbed portion. The author was unable to
make any suggestion as to the reason for such changes. As will be
discussed later in connection with the formation of the cirri, the whole
body seems to undergo a reorganization which apparently is of two
phases: (1) a period of dedifferentiation characterized by the contrac-
tion of the macronucleus and absorption of the old cirri; and (2) a
period of formation of the new macronucleus from one-half of the
original macronucleus and the growth of new organs. In the introduc-
tory paragraph of his well known paper, Wallengren (1901) expresses
this idea concisely, ‘‘ Bei diesen Infusorien (Hypotricha) ist somit auch
eine mehr oder weniger durchgreifende Renovirung der Korper beider
Sprosslinge mit dem Theilungsvorgang verbunden.’’ Calkins (1911)
in a study of the regeneration of Uronychia, operated on before, dur-
ing, and after division, found that the power of regeneration was
greatest in the early phases of division. He explains this power ‘‘on
the supposition that substances are formed in the nucleus and trans-
ferred to the cytoplasm, where they or the products of their activity
accumulate until a condition analogous to saturation is reached.”’
After division is completed and the new organelles are formed, these
substances are used up and consequently the power of regeneration
is lessened or lost altogether.

In the light of recent investigations the results of which have been
brought together by Child (1915) in his book entitled Senescence and
Rejuvenescence, we perhaps are able to put a somewhat different
interpretation on such phenomena as take place in ciliates at the time
of division. Child has shown that in a study of Paramoecium and
Stentor that the earliest indications of binary fission appear not in the
nucleus but in the cytoplasm and that these are followed by the
nuclear changes. Such changes are characterized by the formation of
new cytostomes and contractile vacuoles. He has also proved with
dividing infusorians as well as with some of the flatworms, that at the
time of division the protoplasm loses its high degree of differentiation
and assumes a dedifferentiated or relatively simple condition. Simi-
larly with insects at the time of metamorphosis, some of the larval

372 University of California Publications in Zoology [ Vou. 18

organs are known to go through a disintegration and the whole body
to undergo a reorganization. By subjecting the dividing ciliates, flat-
worms, and segmenting eggs to potassium cyanide, Child proved that
at the time of division when the cells were in the dedifferentiated con-
dition a period of rejuvenescence followed, which was a time when
the rate of metabolism was high. This he claims was an indication
that the tissue was physiologically young and most susceptible to
external stimuli.

This idea of rejuvenescence following the period of dedifferentia-
tion probably serves as a basis for explaining why regeneration in
Uronychia occurs more readily in dividing individuals. The cytoplasm
is young and so responds readily to the call to complete the organisms.
Likewise, perhaps, we can explain the nuclear changes occurring in
Euplotes. Basing our assumption on the evidence brought forth by
Child for different forms, we assume that at the time of division the
cytoplasm of Euplotes has undergone certain dedifferentiating changes
and has assumed a physiological young condition with a greatly in-
creased metabolism. Such being the case it would be necessary for the
macronucleus, the important vegetative organelle of the animal, to
undergo corresponding changes of dedifferentiation and rejuvenescence
in order to properly control the rejuvenated cytoplasm. These changes
in the nucleus are undoubtedly of two kinds, physical and chemical.
The physical changes we are able to witness, while the only evidence
of the chemical changes is the difference in staining reactions, which
with the stains we have used tell us practically nothing of the nature
of this very important phase of the whole reorganization process.

FoRMATION OF NEW CIRRI

A detailed description of the way in which new cirri form is
seareely necessary, since Griffin (1910) gives a very accurate account
of the whole process as found in EF. worcesteri, and the description as
given for that species will well serve for the process as it occurs in
E. patella: the only noticeable point of difference being that EF. patella
has only nine ventral cirri anterior to the anal cirri, while the other
species has ten.

In Euplotes patella, as in other species of Euplotes, the new cirri
arise in two groups and all of the old cirri degenerate. Each group
begins as five depressions in the pellicle, one group immediately
anterior to the anal cirri and the other group still farther forward.

1918] Yocum: The Neuromotor Apparatus of Euplotes, Patella 373

At first these depressions are quite small, but they elongate until four
of them in each group are seen to have the beginnings of three new
cirri in each groove. The depression to the extreme right has only
two cirri forming in it. The posterior cirrus in each row becomes the
anal cirrus. As the animal elongates preparatory to constriction the
depressions in which the cirri form elongate, and the nine anterior
cirri of each group are pulled forward to form the frontal and ventral
cirri. Those which are to be on the posterior animal are carried for-
ward nearly to the five anal cirri of the anterior daughter organism
and are scattered out into something near their ultimate positions.
Since in this description we are much more concerned with the anal
cirri than with the others, on account of our study of the neuromotor
apparatus, we shall not dwell longer on their formation since Griffin
has given such an adequate account.

By the time the five new anal cirri are fairly well formed, the old
anal cirri have begun to be absorbed. The innermost cirrus is the
first to disappear and it is soon followed by its nearest neighbor and
so on in succession, the two toward the right persisting until division
is well-nigh completed. Likewise the old frontal, ventral and marginal
cirri are absorbed and their functions assumed by the new ones.

At first it was thought that the new depressions form in the fur-
rows of the original anal cirri, but this is not the case. Since the
original furrows are rather wide, some of the new furrows do not form
in them. For instance, the new furrow farthest to the right is quite
a distance to the right of the old furrow on that side. The furrows of
the anterior set, especially, bear no relation to the old furrows, but are
much farther apart than the old furrows in that region. Such positions
of the new cirri do not lend any evidence to the proposition that new
cirri form from old cirri. Other evidence against such an idea will
be suggested in a consideration of the formation of the new fibers con-
necting with the cirri.

FoRMATION OF NEw PERISTOME

The formation of the new peristome in Ewplotes patella is prac-
tically the same as that described for E. worcestert by Griffin (1910).
At about the time that the micronucleus migrates from its resting
position to the left side of the macronucleus a slight depression occurs
just back and to the left of the old peristome (pl. 15, fig. 10). This
depression at first seems to be only in the pellicle, but it deepens and

374 University of California Publications in Zoology [ VoL. 18

widens into the ectosare. As it deepens the bottom of the depression
enlarges, making a sack the bottom of which is the original depression.
Very early in the enlargement of the sack a heavy staining line is seen
on the left side of it, which bends to the left and forms a small almost
triangular field surrounded by the dark line. Very early in the
development of the new cytostome there appears in the triangular field
a series of lines lying almost at right angles to the base of the triangle
(pl. 15, fig. 11). These lines are the rows of the basal granules of
the new membranelles. As the depression deepens it also elongates
in the direction of the long axis of the body. With it the triangular
field also elongates and more membranelles form. This series of mem-
branelles increases in length until it reaches about as far forward as
the micronucleus (pl. 15, fig. 12). Posteriorly it elongates some dis-
tance back past the old peristome. In some cases it seems that the
anterior end of the new peristome extends under the membranelles
of the old peristome, but it never comes in contact with them.

As the body of the animal elongates preparatory to constriction,
the new peristome is pulled back past the posterior end of the old
peristome (pl. 16, fig. 18). Both ends of the new mouth become bent,
the anterior end elongating rapidly to follow the constriction which is
cutting the organism in two (pl. 16, figs. 20-21). Thus by the time
division of the body is complete, the new cytostome with its series of
membranelles has nearly assumed its ultimate position and shape.

The opening to the peristome increases in size and by growth and
curvature of the new peristome a triangular adoral field is formed.
The right side of the opening to the new peristome becomes the inner
edge of the anterior ventral field. The series of membranelles grows
over toward the right, keeping almost in contact with the left edge of
the constriction. The anterior end of the triangular adoral field grows
out in a rather rounded protuberance, forming the anterior lip which
comes to lie ventral to the anterior series of membranelles.

When the two daughter cells separate, the right end of the mem-
branelles is at the point of constriction and almost if not quite in con-
tact with the fibers from the anal cirri of the posterior daughter cell.
That this may be quite significant will be brought out in later discus-
sion. The posterior end of the newly formed peristome extends back-
ward and dips down into the endoplasm forming the pharynx.

The above is a rather brief description of the formation of the new
peristome, but it will be seen that the process differs little from that
described by Griffin (1910) for EZ. worcestert. The principal point of

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 375

difference is that EH. patellt has the prominent anterior lip, while in
E. worcesteri this is absent and the right anterior field overhangs the
adoral field much more. Such a depression is heartily in accord with
the idea that the new peristome forms quite independently of the old
peristome. This is more significant than it may appear at first sight.
In our consideration of the formation of the new neuromotor appa-
ratus it will be pointed out that this structure forms from the ectoplasm.
It was also seen that new cirri are of ectoplasmic origin. In the
description of the formation of the new cytostome a heavy staining
line was mentioned as appearing very soon after the depression has
sunken into the ectoplasm. This is undoubtedly differentiated out of
the ectoplasm. Very soon rows of granules form, which are the basal
granules of the new membranelles. These, too, are ectoplasmic in their
origin, for they form on the under side of the pellicle. It is thus
quite evident that the new membranelles form not from the old mem-
branelles but independently in an area quite set off from the old
cytostome. This origin of the new cytostome in EL. patella bears out
the contention of Griffin (1910) that the new cytostome develops quite
independently of the old cytostome and that the whole structure—lip,
eytostomal field, membranelles and basal granules—develops de novo
and are ectoplasmic in their origin.

FORMATION OF THE NEUROMOTOR APPARATUS

We now come to a description of the formation of the neuromotor
apparatus at the time of binary fission, which must be given in its
relation to the other parts which have just been described. Very soon
after the formation of the new anal cirri for both daughter organisms,
there can be seen extending forward from them fine but distinct
fibrils having the same staining reactions as the old fibrils (pl. 16,
figs. 18-21). In appearance they are the same, except that in the early
stages they are much finer and nearer the surface than the old fibers.
Usually the fibers from the anal cirri of the anterior daughter are to
be seen before those from the posterior cirri. Early in their develop-
ment the fibers are quite distinct near the cirri, but as they extend
anteriorly toward the motorium they become much finer and are lost
to view in the cytoplasm. This leads one to the conclusion that the
fibers are ectoplasmic, rather than endoplasmic as Griffin (1910)
stated, and that they grow out from the new cirri toward the anterior
end. The old fibers persist until the new fibers are formed, but with

376 University of California Publications in Zoology [ VoL. 18

the absorption of the old cirri their fibers disappear, apparently being
absorbed in the cytoplasm by dedifferentiation.

At first it was thought that the new fibers fonds by a splitting
of the old fibers, but it was soon seen that such an hypothesis was of
no value for the following reasons: first, the new cirri do not form
along the lines of the old fibers. Those for the anterior cell are as far
apart as the old cirri of the posterior daughter, while the original
fibers in that part of the cell were much converged. Thus the cirri
are not formed in a position where it would be possible for the new
fibers to form by a splitting of the old ones. In the second place, the
new fibers are usually nearer the pellicle than the old ones. As the
cirri become heavier they sink deeper into the ectoplasm and carry the
fibers with them. Then, too, no indication has been seen that would
lead to the conclusion that any splitting of the old fibers occurs. Such
evidence leads one to no other conclusion than that the fibers arise
independently apart from the original fibers.

As was stated in connection with the formation of the new eyto-
stome, there is a line to which the granules of the new membranelles
connect. This inner line becomes the fiber extending along the left
and anterior sides of the cytostomal field. This fiber, too, is then
differentiated out of the ectoplasm in the same way as the other fibers
of the associated neuromotor apparatus. By the growth of the series
of membranelles it is carried forward and around the anterior end of
the cytostomal field. Such growth brings it around in the position of
the new motorium. From this fiber the sensory apparatus of the
anterior lip grows out, but its growth has not been seen before division
is complete.

The formation of the new motorium is the most difficult to make
out. The original motorium remains in the anterior animal and the
new fibers grow forward to connect with it. Due to the unusually large
amounts of food in Euplotes at the time of division, few cases have
been clearly seen in which the formation of the new motorium could
be studied. Plate 16, figure 21, shows a case in which in the anterior
end of the posterior daughter Euplotes a number of bright red granules
could be distinctly seen. These lay at the point where the fibers are
drawn together when the animals were cut apart. As to the origin
of these granules which are the new motorium there are three possi-
bilities: One is that they form where the fibers are drawn together by
the constriction of the animal; another is that the membranelles come
in contact with the fibers from the anal cirri and the fibers form at the

1918] Yocum: The Neuromotor Apparatus of Ewplotes Patella 377

point of contact; a third possibility exists that they may differentiate
independently out of the ectoplasm lke the other parts of the system
and then become connected with the fibers from the cirri and mem-
branelles. The second possibility seems to be the most plausible. The
fibers are always connected with the motorium in a definite way, those
from the anal cirri converging to the inner end of the motorium while
that one from the membranelles always connects to the right hand
end. This could be easily explained by supposing that the fiber from
the membranelles continued its growth toward the right and carried
the granules on beyond the point of convergence of the five fibers from
the anal cirri. The fact that the fiber is continued on beyond the
point where the membranelles and sensory structures develop is evi-
dence in favor of such a conclusion, even though the process of growth
has not been clearly seen, due to the physiological condition of the
animal. By an increase in the number of granules the motorium
attains its normal size.

It has thus been shown that the whole neuromotor apparatus and
the motor organs are derived from the ectoplasm and that their first
indication is a pitting in of the outer surface of the pellicle. This is
quite significant in as much as it is always the ectoplasm that initiates
the separation of two cells. We may carry our analogy still a step
further and suggest the great similarity between the division process
in these organisms, and the same process in all Metazoa which re-
produce asexually in which the ectoderm is the most active in the
separation of the organisms. Such a parallel indicates that the
ectoderm is important in this regard and probably more closely related
to the process of reproduction, especially asexual reproduction, than
we usually think. Such an analagy may be still more closely con-
firmed if we say that the multinuclear condition as found in ciliates
denotes a multicellular condition rather than that of unicellularity,
thus making the ciliates more nearly like Metazoa with their cell
divisions. Thus the analogy between ectoderm and ectoplasm is more
apparent. At least we see from this study of Huwplotes that the
ectoplasm is of much more importance than a mere covering.

378 University of California Publications in Zoology [ Vou. 18

DISCUSSION
FIBRILLAR SYSTEMS IN OTHER CILIATES

The term, neuromotor apparatus, is of late origin, being first used
by Sharp (1913) to denote a new structure found in Diplodinium
ecaudatum. This structure, from its staining reaction and its anatom-
ical relationships, was interpreted as having a neuromotor function.
Few structures like this have been described for ciliates. Engelmann
(1880) was the first to call special attention to such distinct fibers.
These he described in Stylonychia, extending from the peripheral cirri
into the central part of the animal. These have been seen many times
by me on slides made for a study of Euplotes, for Stylonychia and
Euplotes are usually associated in the same cultures. To these fibers
Englemann (1880) assigned a nervous function, but later writers such
as Biitschli (1889), Schuberg (1891), and Maier (1903) discredited
such ideas and instead gave the fibers the functions either of support
or possible contraction. Maupas (1883) found fibers in KHuplotes
similar to those described in this paper as previously noted. Prowazek
(1903) has described such fibers for F. harpa and Griffin (1910) has
found them in E. worcesteri. In these two species of Euplotes the
function of contractility is ascribed to the fibers. Neresheimer (1903),
working on Stentor coeruleus, found certain fibers to which he ascribed
a nervous function. However, he found two sets of fibers in the
‘‘pwischen streifen.’’ One of these he called the myophane, indicating
that it was contractile, the other he called the neurophane, indicating
that it was of a nervous character. There seem certain reasons why
such names are not appropriate: The first of these is that in staining
with Mallory’s stain those structures which have an affinity for the
acid fuchsin are supposed to have a nervous function. In the work
of Neresheimer structures taking this stain are called myophanes.
Secondly and more significant, is the fact that the so-called myophanes
are indicated as being more closely related to the basal granules of
the cilia than are his neurophanes. In the later works, such as that
of Sharp (1913) on Diplodinium and this work on Euplotes, the cilia,
or at least the component cilia of the membranelles and cirri are shown
to be associated with fibers to which are ascribed a nervous function,
not to the absolute exclusion of the idea that they may possibly be
contractile in their function, but with the idea that they are more
nervous than muscular.

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 379

In this light it seems quite apropos to suggest that probably a
reversal of the terms would better indicate the function of these two
sets of fibers in Stentor. Should we ascribe a nervous function to the
myophanes as described by Neresheimer (1903) we might account for
the rhythmical contraction of the cilia, for the contraction takes place
not in the fiber but in the cilium itself, due to the central contractile
axis. Likewise a contractile function might be ascribed to the so-
called neurophanes. It would seem that were these contractile the
contraction of the body would be explained fully as well, even though
they do not extend the full length of the body. To say that they are
of nervous character would seem rather improbable, since a nervous
structure would naturally be expected to be found near the part of
the body which is the most exposed to stimuli and most sensitive.
These neurophanes are not closely associated with the large anterior
cilia which in all probability are more sensitive than the small cilia
covering the body. The other set of fibers is closely associated with
these cilia and the undulating membrane, and it seems from their
relation to these that it is far more likely that they have the nervous
character rather than the so-called neurophanes.

This brings us to the more recent work of Sharp (1913). He
undoubtedly found a structure in Daplodinium ecaudatum which is
comparable to that found in Euplotes patella and described as the
neuromotor apparatus. There is no reason to think that this structure,
composed of fibers going to the motor parts and the so-called motorium
to which the fibers are joined, has a function other than that given
to it by Sharp, namely a neuromotor apparatus with special emphasis
on the neural function. However, it seems in the light of the above
criticism of the work on Stentor that Sharp made a wrong comparison,
for instead of this system of fibers in Diplodinium being ‘‘ probably
comparable to the simple fibers of Stentor figured by Neresheimer
(1903) and regarded by him as ‘neurophanes,’ ’’ they are comparable
to the myophanes. Especially is this true if we can base such a com-
parison on staining reactions and anatomical relationship, for the
fibers of Diplodiniwm are in connection with the basal parts of the
cilia composing the membranelles, a condition very similar to that of
the myophanes of Stentor.

Besides the above mentioned examples there are many indications
that a structure may be found in many ciliates comparable to the
neuromotor apparatus of Euplotes patella and Diplodinium. In
looking over the literature several instances are shown in which there

380 University of California Publications in Zoology [ Vou. 18

is a fibrillar system closely associated with the motor organs and of
structures which may upon further investigation be found to be
nervous in their function.

Probably the one paper which shows the most suggestive examples
is that by Maier (1903). The first striking example given by him is
that of Prorodon teres Ehrbg. In this ciliate there are to be found
lying close to the rows of basal granules of the cilia, fibers which are
called the myonemes. These connect with the fibrillar system around
the mouth. Such a condition recalls to one’s mind immediately the
condition found in Diplodinium, where there is a definite circum-
esophageal nerve-fiber ring. A somewhat similar condition is sug-
gested in Chilodon and Coleps, which also have definite fibrillar sys-
tems surrounding their gullets. In Stentor niger Ehrbg. there is
shown by Maier (1903) in his plate 4, figure 10b, definite end fibers
and basal fibers in connection with the basal granules of the undulat-
ing membrane. Also a system of myonemes is shown close to the basal
granules of the surface cilia. Similar structures are shown in plate 4,
figures lla-b, of Spirostomum ambiguum Ehrbg. The fibers of
Stylonychia have been described in connection with the observations
of Englemann (1880). Maier (1903) also shows in Carchesium poly-
pinum Ehrbg. that the fibers are not in connection with the basal
granules but are very definite in the part of the bell near the attach-
ment of the stalk.

A later work is that by Thon (1904) on Didinium nasutwm O.F.M.
In this organism there is quite a complex system of fibrillae running
from another system of fibrillae around the mouth region to a point
under the nucleus. At this point of convergence Thon was unable to
distinguish any definite body to which the fibers were joined, for in
all well fed individuals the cytoplasm appeared undifferentiated. How-
ever, the fact that here are fibers in connection with the basal granules
and the fibrillar apparatus around the mouth and that these fibers tend
to converge to a point near the nucleus is very suggestive of a struc-
ture similar to that which has been described as a neuromotor appa-
ratus in Euplotes and Diplodinium.

The most recent work which is suggestive of a neuromotor appa-
ratus is that of Braune (1913). He describes a system of fibrillae in
Ophryoscolex purkyngei, a form not distantly related to Diplodiniwm.
This system, he suggests, is composed of elastic supporting fibers, but
he seems to overlook the fact that the animal has an exoskeleton and
other structures which might serve as a skeleton and that, as Sharp

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 381

(1913) has shown, such a function could scarcely be attributed to the
system of fibers. Then, too, their distribution in relation to the motile
parts of the organisms is like that in Diplodiniwm, so that it would
seem that a function of conduction and possibly contraction to a
slight degree, is more nearly correct, as Sharp (1913) has indicated
for Diplodinium.

Of all the above works mentioned, with the exception of the works
on Stylonychia (Englemann, 1880), Stentor (Neresheimer, 1903) and
Diplodinium (Sharp, 1913), none contains any suggestion of nervous
structures, but all seem to consider the function of the fibrillar sys-
tems to be that of contraction or support.

The above brief comment on forms in which there are fibrillar
structures suggestive of neuromotor apparatuses shows us that in all
of the orders of the Ciliata there are to be found in connection with
the basal granules of the cilia, cirri, membranelles and undulating
membranes, distinct fibers which lead out into the cytoplasm of the
cell. In some cases, as Didinium, Euplotes harpa, and Euplotes wor-
cestert, there is a distinct indication that the fibers may converge to a
definite body such as is found in Euplotes patella and Diplodinium
ecaudatum. In others, as Stylonychia, the fibers have been shown to
run out into the endoplasm and fade out. Whether this is the case
or not further investigation alone can demonstrate. At least such
suggestions open up a field which is as yet little developed, and which
will perhaps yield the richest fruits when the work on prepared slides
is supplemented by work of an experimental character.

THe NEUROMOTOR APPARATUS OF FLAGELLATES

The term neuromotor apparatus has been used also to denote a
structure found in flagellates, and there has been worked out within
the last few years a series which indicates a progressive evolution of
this structure in this class of Protozoa. It will be necessary to go
over this series briefly in order to see whether or not the term neuro-
motor apparatus as applied in the study of certain flagellates indi-
eates a structure homologous to that described in ciliates.

The first form in the series is Naegleria gruberi, a soil amoeba which
under certain conditions temporarily changes from its rhizopod form
to that of a biflagellate organism. In her work on this animal Dr.
Wilson (1916) discovered a very primitive neuromotor apparatus.
Flagella arises from a blepharoplast which grows out from the central

382 University of California Publications in Zoology [ Von. 18

karyosome. This blepharoplast is connected with the karyosome by a
rhizoplast. Exflagellation is accomplished by a shortening of the
flagella and a retreating of the blepharoplast into the karyosome. Such
a neuromotor apparatus consists only of a basal granule or blepharo-
plast from which arise two flagella, and a rhizoplast connecting the
blepharoplast to the nucleus. Such a condition is very primitive and
temporary.

Next on the list is Prowazekia or Prowazekella, as Alexeieff (1912)
calls it, which in some phases resembles Naegleria in having no para-
basal body, but in its development a chromidial-like cloud is extruded
from the nucleus and forms a parabasal body connected to the
blepharoplast by a rhizoplast. At the time of mitosis the parabasal
body is depleted of its chromatin but reappears again during the
vegetative phase of the daughter organism.

In Polymastix, Swezy (1916) found four flagella arising from a
blepharoplast which is connected to the nucleus by a rhizoplast and
sometimes to a parabasal body.

In Trichomonas, as described by Kofoid and Swezy (1915), the
neuromotor apparatus consists of three equal anterior flagella, one
posteriorly directed flagellum which forms an undulating membrane
and one axostyle or intracellular flagellum. The parabasal body is a
long chromatin-like rod running along the inner edge of the undulat-
ing membrane. Rhizoplasts connect the blepharoplast to the nucleus
and parabasal body. The axostyle, which serves as the chief motor
organ when the animal is on a surface, contains numerous chromatin
granules which fluctuate in number, arrangement and size, denoting a
kinetic function of the neuromotor apparatus.

Giardia, as deseribed by Kofoid and Christiansen (1915), is a
binucleate organism equivalent to two trichomonad flagellates, each
containing one nucleus, and one blepharoplast at the end of the single
axostyle, three flagella and either a half or a whole axostyle, depend-
ing on the stage of growth of the organism. Around the mouth is a
heavy ring. The two blepharoplasts are connected by cross com-
missures and are anterior. The lateral flagella cross at a median point,
the anterior chiasma. The blepharoplasts are joined to the nuclei by
rhizoplasts and also to the parabasal body lying posterior along the
axostyle.

Thus in Giardia there is a structural basis for coordinating the
two individuals. In reality each half of the organism has its own com-
plete neuromotor apparatus, but due to the crossing of the fibers at

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 383

the commissure between the blepharoplasts and in the anterior chiasma,
two organisms are thus integrated into one individual.

The above series of five examples gives an idea of the progressive
development of the neuromotor apparatus from the simple Naegleria
type to the more complex coérdinating type of Giardia. In all, the
common characters are flagella, blepharoplast, and nucleus. Such a
structural relationship shows that the nucleus is the kinetic center of
all activity. As was shown by Kofoid and MeCulloch (1916) and
Swezy (1916), the parabasal body is not a kinetonucleus but rather
it is a kinetic reservoir, the volume of which fluctuates according to
the physiological condition of the animal.

Homouoay oF NEuROMOTOR APPARATUS IN CILIATES AND FLAGELLATES

We shall now return to a consideration of how far we can homolo-
gize the neuromotor apparatus of ciliates with that found in flagellates.
An homology is rather difficult to establish, but there are at least two
facts which seem to indicate that the structures are similar to a
certain extent.

The first is the homology of the blepharoplast with the motorium,
based upon the relation of these structures to the motor organs of
their respective organisms. As we have seen in the brief review of
the neuromotor apparatus of flagellates, the blepharoplast is the central
structure with which the flagellar apparatus is connected. All motor
organs, both intra-cellular and extra-cellular center upon this one
body. Such a condition is not only true for the uninucleated forms
but is equally true for the multinucleate forms such as Stephan-
onympha and Calonympha as described by Janicki (1915). In these
forms there are many blepharoplasts, each connected with certain
flagella and intra-cytoplasmie fibers, comparable to rudimentary axo-
styles. In all these the blepharoplasts are each connected with a
nucleus.

In ciliates we have a system of structures which at first sight
appear to be quite unlike any structures found in flagellates, but
between which, upon careful analysis, there is a probable similarity.
This similarity exists between the blepharoplast of the flagellate and
the motorium as described for Diplodinium ecaudatum and Euplotes
patella. As brought out above, the blepharoplast is the center around
which the motor structures are built and as such may be taken as the
coordinating organ serving to regulate the anterior and _ posterior

384 University of California Publications in Zoology [ Vor. 18

flagella, axostyle and undulating membrane in such forms as each or
all of these structures may be found. With this idea of the character
of the blepharoplast, it is easy to see how the motorium is similar to
it for the motorium, too, is a structure to which part of the motor
organs are connected. In this case we must consider the basal granules
of the cilia, cirri, and membranelles as being secondary rather than
primary structures. This is interesting in that structures may, in the
process of evolution, develop from the fibrillar system in some such
manner as the development of the ciliary apparatus of the spermato-
zoids of some plants, where a fiber grows out from the blepharoplast
and becomes the band which breaking up forms the granules to which
the cilia are attached (Webber, 1897; Ikeno, 1898). Such a concep-
tion does not permit of comparing the basal granules found in ciliates
to the blepharoplast but makes them of secondary importance, leaving
the similarity existing between the motorium and blepharoplast.

A second point of similarity upon which an homology may be based
is the connection between the neuromotor apparatus and nucleus. In
flagellates such a connection is very evident and consists of a rhizoplast
joining the nucleus to the blepharoplast. In ciliates this connection
has not been definitely established, but in his description of Dzplo-
dinium ecaudatum Sharp (1913) shows that certain fibers connecting
with the neuromotor apparatus extend out into the cytoplasm and end
in the vicinity of the micronucleus. Thon (1904) also described a
system of fibers in Didinium nasutum which extended from the region
of the esophagus to a point near the nucleus. In Euplotes patella
there is no indication that a connection exists between the nucleus and
neuromotor organs, but since other parts of the neuromotor apparatus
so closely resemble the neuromotor apparatus of Diplodinium we may
assume that in the evolution of Euplotes the connection between the
neuromotor apparatus and nucleus has dropped out, and that this
coordinating mechanism at the time of binary fission develops inde-
pendently of the nuclear phenomena. However, such an idea cannot
be completely verified until we know the entire life cycle of Euplotes
and the development of its neuromotor apparatus at the time of
sexual reproduction.

In the above discussion an attempt has been made to show that
even in forms as diverse in structure as ciliates and flagellates there
exist structures which are probably homologous. The motorium and
blepharoplast may be considered homologous structures, both being
centers around which the motor organs are developed in such a way

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 385

as to be controlled by the codrdinating centers. In the probable
parallel evolution of the two groups, the connection between the neuro-
motor apparatus and nucleus has been retained in flagellates but
apparently lost in ciliates, with only an indication of such a connec-
tion in Diplodinium ecaudatum, while in Euplotes patella no trace
remains to indicate that in this highly specialized free-living ciliate
the neuromotor apparatus and nucleus are related structures.

As we look over the literature on Protozoa we are impressed with
the change that has come about in the research done on this interesting
group of animals. The early works had to do with little else than
the classification and the study of external features upon which to
base this classification. The works of Ehrenberg (1838), Stein (1859),
and Kent (1881) are examples of this kind of work. However, with
the improvement of microscopes and better methods of microscopical
technique a more intensive study of the animals was begun from every
point of view. The cytological phenomena, the minute anatomical
structure, life history and economic importance of the Protozoa have
occupied the attention of the investigator and many of the most
common and earliest known organisms have become centers of great
interest.

With all of this study we come to a realization that our old
definition that the Protozoa are simple one-celled organisms is in-
adequate. A study of the soil amoeba as described by Wilson (1916)
shows that even the amoeba which we are accustomed to give our classes
in biology as an example of the simplest form of animal life, exhibits
a complexity not yet understood, while a study of a form such as
Euplotes or Diplodinium shows a complexity unrivalled by many of
the Metazoa, and it seems that the more we learn about them the more
complex they become.

386 Unversity of California Publications in Zoology [ Vou. 18

SUMMARY

This study of Euplotes patella has brought out the following
interesting and significant facts:

1. Euplotes patella is oval in form, coneave ventrally, convex
dorsally. The ventral surface is characterized by the presence of a
large triangular cytostome, the dorsal part of which continues forward
and forms the anteriorly projecting lip; a cytostomal diverticulum,
nine ventral, five anal, and four marginal cirri; a series of mem-
branelles extending along the left side of the eytostome and continu-
ing forward around the anterior end dorsal to the anterior lip. The
whole body is covered by a firm cuticle. The dorsal side is marked
by eleven rows of granules arranged in rosettes.

2. A neuromotor apparatus is present in Euplotes patella. This
structure is composed of a motorium, the probable center of codrdina-
tion, to which are joined five fibers from the five anal cirri and a
fiber which connects with the inner ends of the cytostomal membra-
nelles, and a lattice-work structure in the anterior lip which connects
with the fiber around the anterior end. This system has a probable
nervous function, as is evidenced by its structural relations to the
motile parts of the organism. The ventral and marginal cirri have a
number of fine fibers radiating out from their bases. Their function
is not clearly understood, but they probably represent a detached
dissociated neuromotor apparatus.

Observations show that there is a coordination between the move-
ments of the five anal cirri and the eytostomal membranelles. Vigorous
movements of the cirri are accompanied by increased activity of the
membranelles. Certain reactions to stimuli indicate that the anterior
end is very sensitive to touch. Such coordinated movements and
response to stimuli indicate that the neuromotor apparatus is a struc-
ture which functions as a coordinating mechanism, having the function
of transmitting both motor and sensory impulses, over a system as yet
undifferentiated into motor and sensory nerves.

3. The micronucleus undergoes mitosis and each daughter nucleus
becomes the micronucleus for the daughter Ewplotes resulting from
binary fission. The macronucleus undergoes progressive reconstruc-
tion, beginning at the two ends and migrating toward the middle. The
latter periods of this reconstruction are accompanied by a contraction
of the whole macronucleus. This contraction is not unlike synizesis

ee A ee

1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 387

as found in metazoan germ cells. After this contraction the macro-
nucleus elongates and divides amitotically, half going to each of the
daughter organisms.

4. At the time of division the new neuromotor apparatus is formed
independently of the old one, by a differentiation of the ectoplasm.
The old motorium persists as the motorium of the anterior daughter
Euplotes and the cytosome in the anterior part remains. All cirri are
formed anew and the old cirri and connecting fibers are absorbed.
The new cytostome forms independently of the old cytostome.

5. The changes undergone by the organism at the time of binary
fission indicate a dedifferentiation of the cytoplasm followed by a
rejuvenescence and differentiation into new structures. The macro-
nucleus, which is the controlling organ of the metabolic activities,
undergoes a corresponding reorganization in order to govern properly
the increased metabolism of the rejuvenated organism.

6. The structural relationships of the blepharoplast to the motor
organs of flagellates and of the motorium to the motor organs of
ciliates and the connection between the blepharoplast and nucleus in
flagellates, and the indication of such a connection in some ciliates
suggests that the neuromotor apparatus in flagellates and ciliates are
homologous structures.

388 University of California Publications in Zoology [ Vou. 18

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Prot., 5, 281-321, pls. 12-13, 3 figs. in text.
WALLENGREN, H.
1901. Zur Kenntnis des Neubildungs-und-Resorptions-Process bei der Theil-
ung der hypotrichen Infusorien. Zool. Jahrb., Abth. f. Anat., 15,
1-58, pl. 1, 28 figs. in text.
WEBBER, H. J.
1897a. Peculiar structures occurring in the pollen tube of Zamia. Bot. Gaz.,
23, 453-59, pl. 9.
1897b. Notes on the fecundation of Zamia and the pollen tube apparatus of
Ginko. Ibid., 24, 225-35, pl. 10.
WHITING, P. W.
1917. The chromosomes of the common house mosquito, Culex pipiens L.
Jour. Morph., 28, 523-63, pls. 1-7, 7 figs. in text.
WILSON, C. W.
1916. On the life history of a soil amoeba. Univ. Calif. Publ. Zool., 16,
241-92, pls. 18-23.

EXPLANATION OF PLATES

PLATE 14

Fig. 1. Tangential section showing connection of fibers of anal cirri and
motorium. Mallory’s connective tissue stain. XX 835.

Fig. 2. Cross-section of cytostomal membranelles. Mallory’s connective
tissue stain. XX 1670.

Fig. 3. Cross-section through body. Alcoholic haematin stain. X 535.
Fig. 4. Ventral view of Euplotes patella. X 535.

Fig. 5. Diagonal cross-section through body. Mallory’s connective tissue
stain. X 835.

Fig. 6. Base of anal cirrus and connecting fiber. Alcoholic haematin stain.
x 1670.

Fig. 7. Dorso-lateral view, Euplotes patella. X 535.

Fig. 8. Micronucleus in indentation of macronucleus. Alcoholic haematin
stain. X 1670.

[392]

[YOCOM] PLATE 14

———

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PLATE 15

Fig. 9. Right anterior portion of Euplotes patella. Mallory’s connective
tissue stain. X 835.

Figs. 10-13. Figures to show development of new cytostome. Alcoholic
haematin stain. Figures 10, 11, and 13, X 535; figure 12, X 835.

Fig. 14. Early division stage. Alcoholic haematin stain. X 535.

Fig. 15. Mitotic figure of micronucleus. Alcoholic haematin stain. X 1670.

Fig. 16. Reorganization band of macronucleus. Alcoholic haematin stain.
x 1670.

Fig. 17. Division stage showing contraction of macronucleus and division
of micronucleus. Alcoholic haematin stain. X 535.

[394]

[YOCOM] PLATE |5

18

UNIV. CALIF. PUBL. ZOOL. VOL.

PLATE 16

Fig. 18. Division stage. Macronucleus at maximum contraction. New anal
cirri fibers forming. Frontal cirri not shown. Alcoholic haematin stain. X 535.

Fig. 19. Early constriction. Mallory’s connective tissue stain. X 535.
Fig. 20. Later constriction. Mallory’s connective tissue stain. X 535.

Fig. 21. Division almost complete. New motorium forming in posterior
daughter. Mallory’s connective tissue stain. X 535.

[396]

UNIV. CALIF, PUBL. ZOOL, VOL. 18 [YOCOM] PLATE 16

Mi
) n

Deh aii: WDE te eet ae ee

ayy

aie

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in re ra)
i i j
hit la ek A ad

8

24,

Vol. 17. 1.
: 2.

3.
4,

6.
6.

UNIVERSITY OF. CALIFORNIA PUBLICATIONS— (Continued)
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. The Significance of Skeletal Variations in the Genus Peridiniwm, by re i.
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UNIVERSITY OF GALIFORNIA PUBLICATIONS
IN

ZOOLOGY
Vol. 18, No. 15, pp. 397-47&, plates 17-20, 19 figures in text June 27, 1918

THH SIGNIFICANCE OF SKELETAL VARIA-
TIONS IN THE GENUS PERIDINIUM

BY
A. L. BARROWS Tap
4
p d D0 ves
CONTENTS » JUNI 2 (917
i. PAGE 4
AN, INDIO CNC Ci g/t ee eA LE elt. al “16% a! Lf.) 398: ¥

FAUEPOSeRaMGas Gop enoty Cis) po ep er ese ene eee ee mnee ee 3987
PARC IAMMOMWAL EG ETITCTUGS) ecco ch 5 wee Soh ca ce ee ce 400
Relationships and morphology of the dinoflagellates —_.............2.----------------- 400
WW sveWiatieNpOSsttION: Of Pervdiiwne 2c. <.-c.cccccces cose erect eo teense ceva ee cee 404
Nomenclatuneroty the olates: s.-c.s..c.:ecccacacesess see tee eeenene eae eee ee ee ee 405
1B; INET. pe UNTO 6 ee a Re RE ee eee aS ee eee 408
ASTOSEG GS OLE. GNeGA Die ec Pea ee Meer eee RODE MG ee Ge 8 Seo See cs ne eee oop ere ae 408
Mayorniskeletalscharacters-of Peridinidae) eee ee 408
“AUSTELL ON ICO AYO eee ee eee eae ee ee ee eee 409
Displacementsot the oirdlle. 21ers eee ee 411
TENG OMe ube TMS: -=c20u. 28-20 .. eeh ee 2a es eee 2 ane ee er ae Rn ee aces ee 412
Others ele tal char act emit. 22250 csee ss ee ee ne 414
Conclusions upon the importance of plate relationships -......................- 414
Progressive plate development in genera of Peridinidae ................-.--..----- 416
Possiblenmet hod tor multiplications ot slates sees reset eee 419
hecions of skeletal variation am) Periduniin) sees ere eee 424
Plate patterns, a basis for subdivision of the genus, Peridinium ...............- 426
Sub dinaistonisnot bhies eM US LACT UTU UIT eens ae nero a ee 428
SUG OUUS, LONG DOTUL IVA ag eee: ee se eee eee es RELI terete 428
SHULOSASTUISE, AWC UE WOMMUONIE eoccececetasstcee ee co cenecce hes noeaeegcaeeee weeecee acne secenneeeee see 430
SUID ONNUS GLO) CUCL UT ULETID area ae eee ee 431
Special considerations <2 eae ie ee eee een eee ht ee eee! 435
Summary of changes of plate pattern within a species .......................- 434
Summarys of skele ballin e) ait SLi geese ean anne nem eee UL 455
Regions of variation im the shell of Peridiniwam 22-22-20 ooocec occ neces ART
AAG gb] of Vem eyo Coy hcg ene en eens Oe ek Te Ae a pie Eade ne Ce 437
Oxipine of (themaccessomyaol aes esse naan anes ota ToL 439
Origin of the principal symmetrical dorsal plate patterns -................. 442
Origin of the asymmetrical dorsal plate patterns ..............02000220.2--.--- 443

Summary of discussion of dorsal patterns: occ sc. ceccecceecseecnccscees 443

398 University of California Publications in Zoology [ Vou. 18

PAGE

Paired areas of change: of (late! per titers case cee eee ace aaee 444
Completeness, of thetsertes (Of varia Ons ee eeee ese 446
Geometrical patterns mepres emite Cys eeee ee eee ee tee 446
Combinations so feat te rns yee eae ee eee 446
Variations isthe len oth) ofa rit1c alls ots Cs peeese sae eee eee ne 448
SIGMIACAN CEO VELA LLOM en SU GUO al eM Ob een eee eee one ee 450
Miata vom sissy aes t 2CU on NE eS ee AL Se SE Ee eee ce ens Seen ea ee 456
Possible mmilmentc evo thie me maya: Oia e rit pee ee ee eee eee ae 457

(Cz \©OWCUUSIOTI Sas ek Shee EA AE a ee ee a ee ee 458
STS ABB HG re eD Dy ga oe a es ere eee cee a cera oc eee ce ee ea 466
Hs Plates andmexplama tion's) 10d qolaihes ss ee sees etn te rere ee ete eee ee 472

A. INTRODUCTION
PURPOSE AND SCOPE OF THIS PAPER

The purpose of this paper is to describe certain structural char-
acteristics of the theea of the genus, Peridinium, which have been
used as a basis for the classification of these organisms, but which
seem to have a much more fundamental significance, possibly por-
traying the basis of natural relationships and of speciation. The
theca is constructed with considerable regularity and simplicity in
each species of the group of dinoflagellates to which this genus belongs.
The structure of the theea for different species seems to be based upon
the modification of a given number of parts according to a system
which may be extended to the genera of the greater part of the group.
Not only in Peridinium but also in several other genera of the dino-
flagellates the regions of comparative permanency of skeletal structure
and the regions of variability are usually definitely located. These
conditions give the problem of variability in this group a certain wel-
come discreetnéss.

The group, Dinoflagellata, is also a widely distributed group,
usually abundant wherever found. It contains certain characteristic
cold and warm water forms as well as certain species which seem to
be ubiquitous. Material is thus readily accessible and may be secured
from a great variety of environments.

Moreover, the medium in which these organisms live presents con-
ditions not encountered in the environment of land organisms which
have usually been employed for variational studies. In the sea, of
all places on earth, life may be found under conditions which change

1918] Barrows: Skeletal Variations in the Genus Peridinium 399

less rapidly and through a narrower range of fluctuation than in land
environments. The physical elements into which the marine environ-
ment may be analyzed—temperature, salinity, density, viscosity, light
relations, gas content of the water, ocean currents, ete.—are compara-
tively few, and variations in each of these may be accurately measured.

While the physical conditions of a marine environment are thus
comparatively simple, the absence of concrete barriers in the sea in-
troduces a complexity into the study of the conditions of life for
marine organisms not encountered among land organisms. The con
tinual mingling of waters of all oceans, due to surface currents and
the mixing of surface waters with bottom waters as well, introduce
factors of unprecedented complexity in a study of the biology of
marine organisms. Hence, we have to deal with conditions which
introduce at once the possibility of structural as well as functional
responses to the impact of the environment.

The system of variations suggested in the dinoflagellates, especially
tangible in the Peridinidae, thus offers peculiar attractions for study.
It is the purpose of this paper to describe briefly the systematic posi-
tion of the genus, Peridinium, in the group, Dinflagellata, and among
the Protozoa; to discuss the morphology of the theca of the genus,
Peridinium, and the relations on this basis of Peridiniwm to other
genera of the group, Dinoflagellata, and from this discussion to bring
out the peculiar relations of the patterns of the plates of the theca; to
suggest the significance of variations in the relative sizes of these
plates and of their arrangement into patterns which may possibly
give a clue to the sequence of species in this group; and to suggest
the possible existence of unit characters in the sizes of certain plates.
and the coupling of these characters according to the permutations
permitted by the geometrical relations of the plates themselves in the
formation of species.

It will be suggested that the skeletal characters in this group
apparently may vary independently of one another, or under other
circumstances that they may be linked in groups; that certain char-
acters apparently vary at random about a norm, though there seems
to be a progressive advance in a general direction of specialization ;
that certain characters are evidently accompaniments of old age; and
that of fluctuating factors of the environment the temperature of the
water and its buoyancy may perhaps be the strongest stimuli for the
alterations of structure.

400 University of California Publications in Zoology [ Vo. 18

ACKNOWLEDGMENTS

In working on this subject the writer has been very greatly in-
debted to Professor Charles A. Kofoid, of the Department of Zoology
of the University of California, for the generous use of his personal
library and material, and for direction and advice at every stage,
without all of which this work would have been quite impossible.
The writer is also indebted to the Seripps Institution for Biological
Research at La Jolla, California, for making extensive special collec-
tions at sea on two different occasions, and for the privilege of exam-
ination of other collections of the Institution, and also to the members
of the staff of this Institution for advice upon the problem and
assistance in making the collections. The United States Bureau of
Fisheries has courteously permitted the examination of plankton col-
lections made by the U. 8. 8. ‘‘ Albatross’? in San Francisco Bay and
along the coast of the Pacific states, Alaska, and Japan. Additional
material has been furnished by Professor John F. Bovard, of the
University of Oregon; by Professor Seitano Goto, of the University
of Tokyo; by the Oceanographic Institute of Monaco; by the Biolog-
ical Station of Cette; by the Port Erin Biological Station; and by the
Naples Zoological Station. For the privilege of applying this material
to the problem in hand the writer wishes to acknowledge his gratitude.
Appreciation is also expressed for the privilege of using from Profes-
sor Kofoid’s unpublished work for purposes of comparison a large
number of original and as yet unpublished drawings of Peridinidae
made by Miss Viola M. Bathgate under his direction.

RELATIONSHIPS AND MorRPHOLOGY OF THE DINOFLAGELLATES

The Dinoflagellata form a part of that group of Protozoa, the
Mastigophora, which are characterized by possessing during the
greater part of their life cycle specialized organs of locomotion in the
shape of one or more flagella. Except, however, for similarities in the
form of the locomotor apparatus the Mastigophora present little else
in common, and the several groups brought together in this class often
show closer relationships in other respects to groups outside this class,
such as the Bacteria, Rhizopoda, and Cilata, than to each other.
Classification according to the number of flagella is, therefore, some-
what arbitrary. The Dinoflagellata, however, which are defined not
only by the possession of two flagella, but also by having a shell of
material similar to cellulose in texture and in chemical composition,

1918] Barrows: Skeletal Variations in the Genus Peridinium 401

and by the possession of chromatophores in some surface forms, con-
stitute a group which is evidently bound together by intimate phylo-
genetic relationships.

Among this vast assemblage of parasitic as well as free living
organisms included among the Mastigophora, the Dinoflagellata
(Bitschh) are the largest group which is found extensively in the sea.
The other free living Mastigophora are found largely in fresh water.
In the sea the dinoflagellates seem, however, to have multipled in
ereat variety, doubtless originating there in an early geologic period.
Because of the purely organic nature of the shell of these organisms
dinoflagellates have been rarely found preserved as fossils, but a few
figures are given by Ehrenberg of specimens from horn stone (similar
to flint) from Delitzsch, Saxony (1854, pl. 37, fig. VII, 1, 3, 4); from
Pottschappel, Saxony (1854, pl. 37, fig. VII, 3, 4); and from coral-
crag formations of Krakow, Poland (1854, pl. 37, fig. VIII, 1), and
also from blackish-brown, leaf-coal measures of Westwalde, Germany
(1854, pl. 7, fig. If, 18-15). These, however, seem to have been so
poorly preserved in most cases as not to permit definite descriptions
or classification, though more or less of a plate pattern is discernible
from some of Ehrenbere’s drawings.

Only a comparatively few forms of dinoflagellates have adapted
themselves to fresh water conditions, having been carried thither from
the sea or from brackish water areas, most probably by water birds
or in spray whipped into the air by the wind and deposited with
atmospheric dust (ef. Ehrenberg, 1854, pl. 7, fig. B, 3). These: fresh
water forms suggest, from their close relations to the more highly
developed of the dinoflagellate types rather than to the more simply
organized and presumably more primitive types, a transition from the
sea at a comparatively recent geologic period.

The dinoflagellates are, moreover, a fairly well known group.
Extensive investigations upon them date from the time of Ehrenberg’s
first descriptions in 1830. Because of their abundance and impor-
tance, they have received much attention and the literature dealing
with them has become very large. Hundreds of descriptions are
recorded among which there must be over six hundred valid species.

The flagella in dinoflagellates commonly originate in the region of
a pore, located on what is termed the ventral side. One flagellum
cirecumseribes the body of the organism in a groove, the girdle, located
according to the genus near the anterior end or about the midregion.
The other flagellum trailing posteriorly lies in a more or less well

402 University of Californa Publications in Zoology [ VoL. 18

defined depression, the longitudinal groove or sulcus, which is regarded
as ventral in position. In function the longitudinal flagellum imparts
the forward motion and the transverse flagellum imparts a rotary
motion. By means of this rotary motion spiral progression in a
fairly straight line is secured, which would otherwise be impossible
on account of the asvmmetry of the organism. The margins of
these grooves, especially of the transverse groove, carry hyaline lists,
or wings, apparently supported by stiffened ridges or ribs. The pur-
pose of these grooves with their extended hyaline margins as recep-
tacles for the flagella is probably to serve as flanges to increase the grip
of the organism upon the water, and to make more effective the beat-
ing of the flagella, thus facilitating the rotation and locomotion.

The transverse groove or girdle divides the shell into two distinct
portions, the anterior of which is known as the epitheca and the pos-
terior as the hypotheea.

The shell of the dinoflagellates has been shown by analysis to be
composed of an ashless substance similar to cellulose. At certain
stages of the life of an individual this shell is homogeneous and un-
broken. Through a breaking down of certain parts of the shell along
pattern lines peculiar to each group and species, the shell is divided
into a number of plates. The cellulose substance seems to break down
at the suture lines of the plates and to be replaced by a cement which
yields to dissolving alkaline reagents which have little effect upon the
cellulose of the plates themselves. The joint at the sutures is beveled
and corrugated (Kofoid, 1909) and it seems probable that limited
growth with age is permitted by the widening of this beveled edge
through the addition of shell material on the margin of the plate.
The great differences in the appearance of the sutures varying in dif-
ferent individuals from narrow, highly refractive lines to wide, stri-
ated tracts are regarded as due to the widening of the sutures to
accommodate the internal pressure of growth with age. Significant in
this connection is a chain of Gonyaulax figured by Kofoid and Rigden
(1912), showing the increase in size with successive asexual divi-
sions from a single individual, as demonstrating the possibility of
increase in size in this method of reproduction, and hence the prob-
able potentiality of dinoflagellate protoplasm for growth without
actual division, provided means for alleviating the confinement of the
shell can be secured, such as growth of the plates on thin edges.

The plates of the shell may be variously marked, though in many
species the shell may be nearly if not quite smooth, or covered with

1918] Barrows: Skeletal Variations in the Genus Peridinium 403

spines, or by a ridged reticulation with spines at the intersections of
the ridges or even with papillae so large as to give a corrugated ap-
pearance to the shell (e.g., Peridinwm thorianum). In addition to
external markings, there is much evidence of the frequent if not uni-
form occurrence of perforations in the plates and of the existence of
a thin membrane of protoplasm outside of the plates.

The protoplasm of many species carries chromatophores of yel-
low, brown, or green, and oil globules which may be associated with
the phosphorescence of many species under certain conditions.

Nearly all members of the family, Peridinidae, are markedly
asymmetrical, both laterally and dorso-ventrally. In Triposolenia
Kofoid (1910) has shown that this asymmetry is of undoubted benefit
in so orienting the organism as it falls through the water at periods
of quiescence as to cause it to present as great a surface as possible
in the direction of the fall, thus retarding its rate of falling. The
asymmetry of many species of Peridiniwm and of other genera may be
explainable upon a similar basis.

The anterior or posterior end of a dinoflagellate may be produced
into hollow horns or may carry spines apparently of solid material
and supported by lists in the manner of buttresses. In forms with
long, hollow appendages or horns, notably in species of Ceratium,
autotomy of these horns has been observed (Kofoid, 1908) and has
been explained as an adaptation to flotation upon sudden changes in
the density of the surrounding sea water.

Among the dinoflagellates a number of features fortunately com-
bine to make the genus, Peridinium, a favorable subject for such an
inquiry as this:

(1) The great abundance of certain species of the genus, and their
wide distribution, affording a possibility for comparing representa-
tives of the same species from regions presenting a great variety of
conditions ;

(2) The morphologic features of these organisms which lend them-
selves readily to a systematic comparison ;

(3) The nature of the environment itself offering a new point of
view on account of its differences from the land environment under
which these problems have usually been studied ;°

(4) The existence in an environment which is unusually stable
and free from rapid or extreme variations, and which from many
aspects seems to be as simple an environment as can be found in any
considerable area of the earth, and an environment which may be

404 University of California Publications in Zoology [ VoL. 18

supposed to approximate as nearly as possible early primitive condi-
tions under which organic life may have existed, and under which, to
judge from the fossil remains of other groups of Protista, Foramini-
fera, Radiolaria, and Diatomacee, for instance, there has been a mini-
mum or at least a very slow evolutionary change from the forms of the
Carboniferous seas to those of the present ;

(5) The complheations, on the other hand, introduced because of
the lack of conerete barriers in the sea, making physiologic barriers of
especial importance ;

(6) Life in an environment without a substratum and one in
which the maintenance of an organism under optimum conditions
depends upon the continuance of its active functions or the rapid
adjustment between surface area and volume of the organism, per-
haps necessitating for the pelagic plankton further adaptation by
means of resting stages during long periods of severe conditions ;

(7) The vital importance of minute variations either initiated
within the organism or stimulated by the stress of the environment,
and the significance of small measurable variations in any of the
physical factors of the environment, illustrating the delicate balance
which must be maintained between these organisms and their environ-
ment if they are to continue their existence.

SYSTEMATIC POSITION OF PERIDINIUM

Recent taxonomic arrangement recognizes two orders in the sub-
class, Dinoflagellata, of the Mastigophora; the Adinida containing
the genera, Hxruviaella and Prorocentrum, in which ‘‘the typical
peculiarities of Dinoflagellate organization are not fully developed”’
(Minchin, 1912, p. 278), and the Dinifera, having the typical charac-
teristics of the subclass (Minchin, 1912, p. 278; Doflein, 1911,
pp. 525-531).

The order, Dinifera, is in turn regarded as composed of three com-
prehensive families, the Gymnodinidae, Peridinidae, and Dino-
physidae. The Gymnodinidae are distinguished as being shell-less, or
at least without a shell which has been divided into plates and which
may be visibly distinguished as a structure set off from the main
protoplasmic mass of the body. There is indeed some suggestion that
some of the forms now placed in this family may be only incompletely
developed forms of the next family, in which the shell characteristic
of the adult stage, usually met with, has not been fully developed.

1918] Barrows: Skeletal Variations in the Genus Peridinium 405

Representative genera of the Gymnodinidae as at present considered
are Pyrocystis Murray, Gymnodinium Stein, Blastodinium Chatton
(parasitic), Oxyrrhis Dujardin, and Pouchetia Schiitt.

The family, Peridinidae, contains the typical members of the
group and is characterized by the full development of the general
characters of the group, including especially a ‘‘well developed cuirass
made up of definite plates’’ (Minchin, 1912, p. 278) and two flagella,
one lying in a transverse groove or girdle, and the other trailing pos-
teriorly from a ventral longitudinal groove. It is with this division
of the dinoflagellates that we shall be principally concerned. The
representative genera of this division will be named later.

The third family, Dinophysidae, containing a number of bizarre
forms, differs from the Adinida in possessing a well-defined girdle
often with very large girdle lists which may extend along the margins
of the longitudinal groove as well, and differs from both the Gym-
nodinidae and Peridinidae in having the shell divided into two lateral
valves by a sagittal suture. Each valve is in turn divided into one
large and one small plate by a portion of the girdle which usually lies
well toward the anterior end of the organism. Representative genera
are Dinophysis Ehrbg., Phalacroma Stein, and Ornithocercus Stein.
From the fundamental skeletal character of a sagittal suture, it is
possible that the Dinophysidae may be more closely related to the
order, Adinida, which contains evidently the most primitive and gen-
eralized forms of the group, than to either the Gymnodinidae or the
Peridinidae, and that the bizarre development of the lists, ete., is of
secondary morphologic importance and perhaps acquired rather late
in the phylogenetic history of this portion of the group.

NOMENCLATURE OF THE PLATES

In this paper the system of plate nomenclature devised by Kofoid
(1909, p. 40) has been adopted as being at once the simplest, most
logical, and most adaptable by extension to related genera, of several
which have been proposed and which have been summarized by Kofoid
(1909, p. 44). This system recognizes the girdle as a basis of refer-
ence rather than a hypothetical equatorial plane, with which the
girdle rarely exactly corresponds on account of its more or less spiral
course. The girdle is, moreover, the most prominent single feature of
the organism and it hes in such a position relative to the plates in
Peridinium and in related genera that it is especially convenient to use

406 University of California Publications in Zoology [ Vou. 18

it as a basic feature in composing a system of nomenclature. From
this basis of reference the plates in Peridinium at once appear as
arranged in circumferential rows, one row on either side of the girdle,
the precingular row and the postcingular row; one group, the apicals,
about the anterior pole or apex; an incomplete row interpolated be-
tween the apicals and the precingulars, the anterior accessory plates ;
and in this genus, a pair of plates over the posterior end, the antapi-
cals, carrying the antapical horns, and representing an antapical row.

Each plate is designated by a composite symbol of which one
factor, the superscript written as a prime point indicates the row, the
rows themselves being designated by one, two, three, or four prime
points as they oeceur in succession from the apex posteriorly. The
incomplete row of anterior accessory plates is designated by the
superscript a. In each row the plates are numbered from the left to
the right of the organism coincidently with the direction of the course
of the transverse flagellum. This direction for numbering is, as one
looks at the organism from the anterior end, counter-clock-wise for
the epitheca and as seen from the posterior end, clock-wise for the
hypotheca. This order of numbering corresponds to the usual method
for numbering serial parts distally from the proximal portion.

Thus, in Peridinium the apicals are numbered from 1’ to 4’, the
anterior accessories from a 1¢, to 3%, the precingulars from 1” to 7”,
the postcingulars from 1’’’ to 5’’’, and the antapicals 1’’” and 2’.
This system permits the writing of a simply expressed formula for
the plate relations, the number of girdle plates being inserted with-
out superscript or if desired for completeness with the superscript ¢
(which, however, has not been used by Kofoid). For a typical species
of Peridimum the plate formula would then be 4’—3°—7’-39-5’/’-2’/"".

This system presents much practical convenience. The numerals
as symbols more rapidly indicate the relative position of a plate in its
row than do the letters used by Biitschl (1885, p. 928), Fauré-Freimet
(1908, p. 215), Stein (1883, pl. 10, figs. 1, 6), and Broch (1912, fig. 8),
while the superscript indicates at once the relative position of the row
antero-posteriorly. Not the least favorable feature of Kofoid’s system
is its elasticity and adaptability to any member of the eroup of dino-
flagellates which has a skeleton made up of discreet plates.

This system of nomenclature, however, is based on more funda-
mental grounds than those of mere convenience. The fact that this
system, regarding the plates as grouped in circumferential rows, holds
throughout a large portion of this extensive group is in itself signifi-

1918] Barrows: Skeletal Variations in the Genus Peridinium 407

cant in supporting the suggestion that the origin of the plates of the
dinoflagellate skeleton is by the fragmentation of an originally homo-
geneous shell cirecumferentially rather than meridionally, and that
other plates though derived from the plates of this or secondarily
formed rows still preserve this arrangement.

Kofoid’s system has certain points in common with that of Stein
and of Biitschli in recognizing rows of plates and in enumerating
these in a left-to-right direction. Broch (1912, p. 39, fig. 8) in his
figure recognized the arrangement of the plates in rows, and so does
Fauré-Fremiet (1912, figs. 3-14), though the figures of Fauré-Fremiet
suggest that he conceived of the apical plates as lying in three meri-
dional rows in addition to the rhomboid plate. The implication from
the nomenclature of these figures is that Fauré-Fremiet regarded the
accessory plates as derived by splitting off from the apicals, while the
implication from the nomenclature of the accessory plates in Broch’s
(1912, fig. 8) figure is that these accessory plates may have been
derived from the precingular plates. There are indications of shape
in many of the plates, however, which make the manner of origin of
the accessory plates doubtful. In view of this lack of more definite
knowledge upon the origin of the accessory plates, Kofoid’s system
committed by implication to neither view would seem to be the more
conservative. The rhomboid plate in Kofoid’s nomenclature is re-
garded as an apical which has not divided but which has become
extended to meet the girdle.

The plates of the ventral area seem never to have received a defi-
nite nomenclature, probably because of the great difficulty in deter-
mining them. On account of the considerable variability of form
and extent of the ventral area in different species it is to be expected
also that the plates of which it is formed will display much variation,
and this has been demonstrated for shape as well as number in several
forms already worked out. A system of nomenclature for the major
plates of the theea in order to permit expression of the relationships
of the various groups of the dinoflagellates need not include, there-
fore, the ventral area in its consideration, for the main relationships
of the dinoflagellates seem to be sufficiently if not mainly expressed
in variation in the arrangement of the major plates of the theca ex-
elusive of those of the ventral area.

408 University of California Publications in Zoology [ Vou. 18

B. MAIN ARGUMENT
ABSTRACT OF ARGUMENT

The cellulose-like shell or skeleton of the genera of Peridinidae,
biflagellated Protozoa of the sea, shows a progressive specialization
in the increasing number of plates into which the skeleton is divided
in the several genera. This process of specialization can be traced in
detail in species of Peridinium, one of the principal genera of the
family. Among the species of this genus the arrangement of the
plates in four regions on the anterior part of the skeleton undergoes
definite changes, producing different plate patterns limited in num-
ber by the geometric possibilities for the rearrangement of the plates.
These plate patterns are not only of great convenience in classifica-
tion but because of the fundamental morphologic importance of the
skeleton, the arrangement of its elements may be relied upon to show
the relationships of many of the species of the genus. As represented
in these species, each pattern is distinct, and transitionary stages from
one pattern to another are unknown. Exceptional cases, however,
have been found of specimens which, while bearing many character-
istic marks of a certain species still display a plate pattern different
from that typical for the species.

It is strongly suggested that each pattern represents a condition
of skeletal equilibrium which is disturbed only by an accumulation
of stress, due perhaps to some unusual environmental condition, and
that when thus disturbed the plates fall into an entirely different
plate pattern, much as patterns change in a kaleidoscope. The indi-
cations are, then, that in this genus species formation takes place
by changes which are in the nature of saltations, rather than by means
of fluctuating continuous variations.

Masor SKELETAL CHARACTERS OF PERIDINIDAE

Upon attempting to arrange the large number of species which
come under the definition of the genus, Peridinum, upon a systematic
basis useful for the taxonomist and expressive, so far as possible also,
of the natural affinities of the members of the genus, three prominent
skeletal characters present themselves for consideration. These are:
(1) the type of the antapical horns; (2) the direction of the dis-

1918] Barrows: Skeletal Variations in the Genus Peridinium 409

placement of the ventral ends of the girdle; and (3) the suture pat-
terns formed by the varied arrangements assumed by the plates of
the shell.

Type of Antapical Horn.—F rom the prominence which the ant-
apical horns assume in many species of the genus, one is tempted to

4' a!
” é i! : he
7" 7"
@ @ @

Metaperidinium Orthoperidiniurm

VARIATIONS IN PLATE PATTERN OF PERIDINIUM

Fics. 1-16.—Diagrams of the arrangement of the ventral plates of the
epitheca in the three subgenera of Peridiniwm and for the several arrangements
of the dorsal plates, showing in the series of figures from 9 to 12 the two
probable methods for the introduction of the accessory plates and the develop-
ment of the accessory row to the three-plate stage. Figures 13-16 indicate in
the small triangles the regions at which the early accessory plates may have
been introduced. (Figures 2, 13, 14, 15 and 16 have not been authentically
reported in specimens). Figure 4b, is only a variation of the pattern for the
subgenus Orthoperidinium, as given in figure 4a.

410 University of California Publications in Zoology [| Vou. 18

consider the type of horn as a primary basis in dividing the genus
into its general divisions. Two different types of horns arising from
the antapical plates are found in the genus, each represented in a
well-developed fashion in a large number of species.

One of these types of antapical horns is formed by pushing out the
center of each antapical plate ot a greater or less extent, thus forming
a hollow horn which often becomes a large and prominent feature at
either side of the posterior end of the longitudinal groove which ter-
minates between the two horns. A spiny tip is often present at the
end of this hollow horn. The lists of the longitudinal groove which
are continuous with the posterior list of the girdle pass over the inner
bases of these horns and unite around the end of the longitudinal
groove. Occasionally, as in P. cummingii Lemm, a fresh water form
having four horns, the hypotheea may be pushed out to form sharp
but hollow horns on other plates than the antapicals, or a general
elevation of the center of each antapical plate may terminate in two
or three sharp tips, as in P. crassipes Kofoid.

The second type of horn seems to be quite unrelated to the former
types and consists of a solid spine, buttressed by three hyaline vanes,
two of which are continuous, except perhaps for a deep notch in the
vanes at the base of the spine, with the lists of the longitudinal groove.
The third vane lies on the opposite side of the spine from the longi-
tudinal groove. The spines are usually located upon the antapical
plates, but stand rather nearer to the longitudinal groove than do
the hollow horns. This type of horn reaches its greatest development
in such examples as P. steinii Joerg. and P. tenuissimum Kofoid.

It seems probable that this latter type of spine arose directly as a
support for the list of the longitudinal groove and thus independently
from the hollow type of horn and for a different purpose. In such a
species as P. crassipes, in fact, the incompletely developed stages of
both types of horn may be seen, the spiny type supporting the list of
the longitudinal groove and the hollow type represented by two or
three points arising close together from near the center of each ant-
apical plate and producing the peculiar ‘“‘flat-footed’’ appearance
for which the species was named.

While in most species of Peridinium one type or the other of horn
is distinctly in evidence, there are species in which not only is there
no sign of elevation of the antapical plates to form the hollow type
of horn nor are the lists of the longitudinal groove high enough to
need support and even the spiny type of horn is indiscernible. This

1918] Barrows: Skeletal Variations in the Genus Peridinium 411

character of the type of horn seems an insufficient basis, then, for the
differentiation of all the species of the genus. From its variable de-
velopment, moreover, throughout the genus the type of horn seems
not to represent a sufficiently profound condition in the organization
of the genus to merit recognition as a feature capable of dividing
the genus into two morphologically correlative portions. And it is
hardly to be supposed that in the presence of so many prominent
variable characters as those of which Peridiniuwm is possessed a single
one might have been selected to direct the progress of evolution into
two paths. Though perhaps a practical convenience in taxonomy as
affording a basis for the ready identification of specimens, this char-
acter of the type of antapical horn can hardly be presumed to have
monopolized the early differentiation of the genus.

Displacement of the Girdle-—Although the relations of the girdle
are undoubtedly correlated with the function of locomotion in a very
important way, it has not as yet been demonstrated that rotation of
these organisms is dextrad in certain species and sinistrad in others
according to the direction of deflection of the girdle, nor in which
direction this rotation takes place in those species in which the girdle
ends meet approximately opposite each other. Variations in the
amount of deflection also occur even in the same species. We are not
dealing here with the character of the presence or the position of the
girdle itself but merely with the relations of the ends of the girdle.
On the whole it does not seem probable that a character of such lim-
ited extent in the morphology of these forms could have assumed a
dominating influence in effectually dividing the genus into two cor-
relative parts.

As a practical aid in gaining an acquaintance with the genus,
however, this character has been of considerable value. Early classi-
fiers, Schiitt, Bergh, and Gran, divided the genus abruptly into two
portions on the basis of the deflection of the distal end (right end
from viewpoint of the organism) of the girdle anteriorly or posteriorly
with respect to the proximal end through which passes the base of
the circumferential flagellum. Coupled with the character of an-
terior deflection in the division of the genus called Protoperidinium
was placed the character of the solid buttressed antapical horns, and
with the character of posterior deflection was coupled the character
of the hollow antapical horn to-define the remaining portion of the
genus, Euperidinium. This pairing of characters, however, does not
always hold throughout the genus. Moreover, in many species it is

412 University of California Publications in Zoology [ Vou. 18

impossible to determine any deflection of the girdle. In practical
application Paulsen (1908) continued this basis of classification, sub-
ordinating to it the characters of presence or absence of antapical
spines, the type of spine, shape of the body, ete.

Fauré-Fremiet (1908) divided this genus into four groups upon
the basis of the total of resemblances including form, type, and devel-
opment of horn, ete.

Meunier (1910) used girdle characters also in beginning the classi-
fication of the genus, but considered first the character of the girdle,
whether flat and winged or impressed into the body of the organism
and not winged.

The wing or hyaline list is, however, too superficial a structure to
claim far-reaching significance. Meunier’s system of classification
may be presented as follows:

A. Planozones, girdle flat or but slightly, if at all, impressed,
winged.

I. Girdle sinistro-spiral, e.g., P. divergens.
II. Girdle dextro-spiral (subdivided according to proportions
of major axes; including the larger portion of the genus).

B. Cavozones, girdle excavated, not winged, more or less clearly
sinistro-spiral, if not circular, e.g., P. thorianum, P. concum.

Meunier added also a short list of small forms which he finds it
difficult to insert elsewhere in his system. Examination of this system
reveals many misinterpretations of structure, if not errors in deserip-
tion, so that it cannot be retained as a useful contribution in revealing
the relationships of the genus.

Plate Patterns.—Although descriptions of species had for many
years previous often been based upon the characters of plate pattern
as reported in sketches, together with the features of size, shape,
surface markings, ete., it was not until 1912 that a comprehensive sys-
tem for the whole genus was proposed on the basis of plate relation-
ships. Joergensen (1912) recognized on the ventral surface of the
epitheca two main groupings of the plates in this genus, those given
in our figures 3 and 4a, but he mentions also a third grouping which,
however, he regards as unimportant because of its infrequent occur-
renee, and probably only an exceptional occurrence of the pattern
of figure 1. He divides the genus primarily into two major sub-
divisions, giving the name, Orthoperidinium, to those species having
the plate pattern of figure 4a, and Metaperidinium to those species
having the plate pattern of figure 3. To the remaining occasionally

1918] Barrows: Skeletal Variations in the Genus Peridinium 413

occurring forms having plate pattern of figure 1 he gave the group
name, Paraperidinium, but in his later treatment he merged this
group under Metaperidinium.

Joergensen also recognized that in both of those groups having
plate patterns 3 and 4a and named by him Metaperidinium and
Orthoperidinium, respectively, three different dorsal patterns of the
plates of the epitheca also occurred. He accordingly redivided each
primary subdivision of the genus on the basis of the dorsal pattern,
and established under Metaperidiniwm a seventh place for the few
erratic species having the pattern of Paraperidinium for the ventral
epithecal plates. Though certain corrections and amplifications may
be made in this system as given by Joergensen, its formulation was a
great step in advance toward a fuller and more correct understand-
ing of the organization of the genus than had previously existed.

Pavillard (1916) summarizes Joergensen’s system as follows:

Orthoperidinium
See. I. Tabulata
e.g., P. tabulatum
Sect. II. Conica
e.g., P. conicum
Sect. ITI. Oceanica
e.g., P. depressum

Metaperidinium
Sect. IV. Pyriformia

e.g., P. stein
Sect. V. Paraperidinium

e.g., P. pallidum
Sect. VI. Humilia

e.g., P. ovatum

Sect. V. Divergens
e.g., P. crassipes

Pavillard (1916) criticizes Joergensen’s system on the basis that
there is no real relation between those members of the group Ortho-
peridinium and Metaperidinium, which have the same dorsal pattern,
nor between the species of these two subgenera differentiated by hav-
ing different dorsal patterns and connected on the basis of similar
ventral patterns, as members of linear series. Pavillard accordingly
proposed another grouping of these seven subdivisions, accepting in
the main Joergensen’s definitions based upon plate patterns. Pavil-
lard also finds a few species which cannot be included in any of these
seven subdivisions which he appends as ‘‘Incertae Sedis.’’ P. curvi-
pes, P. mite, which are said to intergrade, and P. rectum, said to be
unstable.

This historical resumé of the various bases for classification in this
genus has been introduced to show the recent trend toward recogni-
tion of the importance as well as the convenience of the pattern of
the plates in the organization of the genus.

414 University of California Publications in Zoology [ Vou. 18

Other Skeletal Characters—This present trend to regard the
skeleton of dinoflagellates as of greater and greater value seems to
reflect the more and more nearly complete recognition of the morpho-
logical importance of this part of the structure of these organisms.
Nor is it unreasonable to look among the dinoflagellates, as we do
among almost all other groups of animals which possess skeletal struc-
tures of any sort, both internal and external, to the hard parts of the
organism for the reflection of the deep-seated processes of change.
Hard parts of organisms seem in all groups to be modified but slowly
either by hereditary influence from generation to generation or by a
possible impress of the environment. The fundamental connections
of related animals seem to be impressed upon the more permanent of
the structures. Particularly is this the case when the hard parts are
not composed of excreted extraneous material, but are retained in a
close relation to the living protoplasm of the organism.

Of the characters of the skeleton of Peridinidae there are several
which may contribute more or less to an understanding of the rela-
tionships of the members of the family. The nature of the antapical
horns has already been discussed and the inadequacy of this character
to serve even in first instance as a common divisor for the genus,
Peridinium.

Size is of course an important character, but is so dependent upon
the extremely variable metabolic processes involved in the whole
course of food assimilation and of excretion as to be hardly trust-
worthy to reveal far-reaching generic relationships.

Shape is an important factor, but in view of the well-known
capacity for autotomy among the dinoflagellates and for individual
responses to protoplasmic pressure, the shape of an organism seems
to be too intimately under the control of the environment and is not
to be trusted to display an all-pervading set of relationships.

Characters of the surface of the skeleton are also of a certain
value, and with the shape should be taken into consideration in the
confirmation of relationships proposed on any other basis, but this
character again is under direct influence not only of the environment
but also of age because the degree of the development of surface
markings is known to vary widely not only between species but also
between individuals of the same species presumably of different ages.

Conclusions upon the Importance of Plate Relationships.—The
number of parts of which the skeleton is composed seems, however,
to be a much more fundamental thing than any of the characters just

1918] Barrows: Skeletal Variations in the Genus Peridinium 415

discussed, and to be second only in its significance to the presence of
the skeleton itself. The facts that the skeleton throughout the whole
group of Peridinidae is found to be divided into plates, that through-

CREEESUDDR Sees SeSeSRnLes
SED BE RESSEE se Eeonaa Be

QEERALEESSSSeSSe Las
SauuGEGENETSSSETSREIT a SESPRGREET EDA TE Tear TeaeaCTeaere
BEER EEE ee ee Eee

Fic. 17.—Chart of measurements of critical sutures of the ventral Seats
plate patterns for 44 and 46 specimens of Peridiniwm divergens Ehrbg., 1.e.
the sutures between plates 1’ and 2” on the left and between 4’ and 7” on the
right. Note that from the distribution of the specimens measured, as shown
in the charts for geographic races, there is nothing to indicate a cause for the
double or triple crests either in these charts or in those of figure 18. This
multiplicity of the crests must, therefore, be regarded as purely accidental.

416 University of California Publications in Zoology — | Vou. 18

out decades of study the number and arrangement of these plates
have been found to be sufficiently constant to be relied upon as bases
for the descriptions of genera; and the system of rows of plates upon
which the whole matter of plate arrangement seems to rest, extensible
to all the genera of this large family, are other considerations which
still further suggest that certain group relationships are to be revealed
in a comparison of the plate formulae when taken into account
together with other skeletal features which may in one part of the
genus or another be of phylogenetic importance. There is indeed no
other character which reveals more, not only of the detailed but also
of the general relationships of the Peridinidae, than this character of
the development and arrangement of the plates of the shell.

PROGRESSIVE PLATE DEVELOPMENT IN GENERA OF PERIDINIDAE

We find ourselves confronted in viewing the family Peridinidae by

a considerable assemblage of genera which can be arranged in a series
according to the number of plates composing the skeleton. All of
these genera have at least four circumferential rows of plates and
several genera have one or more plates of a partially complete acces-
sory row. At one end of this series stand such genera as the following :

Ceratium,—4’—03—§'"49-5'”"—0P-2'7”’

Protoceratiwm,—2’—0*—6” ( 1)—68 (2) ’””—0P-3''”"

Goniodoma,—1 (to 3)’—09—7''—(2) &-5’""—0P—2”””"

Heterocapsa,—4 (or 5)’—0*—5 (or 6)/’—?8—5/’"—0P-2''”"

Pyrophacus,—4 (to 6)’/—0*-0 (to 12)’?8-9 (to 12)’”’-0P—(3 to 5)’”’

The last genus mentioned is especially noteworthy because of the
large number of plates contained in each row.

In another group of genera an incomplete row of plates has been
introduced on the dorsal side of the epitheca or of the hypotheca or
of both, such as the following:

Heterodiniwm,—3/—12—6/18—7'/’—0P-3/""
Gonyaulaz,—-1 (to 6)’—0 (to 4)*—6””—6&-6’"”—]P—-1/”””
Centrodinium,—2 (to 4)’—03—6’’—?8—6/"-]P_-4”"”
Spiraulax,—4'—1*—6’—6&—6///—-1?-1/"”"
Peridinium,—4/-0 (to 3)*—7’"-38—-5/’—0P—2/'”"
Perindinella,—4’/—0 (to 3) *=-7/"—38-5!""—0P-2/"”"

It is not possible to arrange all of these and the other genera of
this family in a strictly linear series because of the two ways, at

least, in which the number of plates of the shell seem to differ, 7.e., in
the number of rows and in the number of plates in each row. More-

1918] Barrows: Skeletal Variations in the Genus Peridinium 417
over, the actual genetic relationships may be influenced more or less
by variations in other factors than that of plate pattern, though
probably on the whole not so profoundly. Suffice it to show, how-
ever, that these more or less closely related genera differ markedly in
the number of plates into which the skeleton is divided. If any num-
ber of these genera arose from a common stock or if one of them is
derived from another, it must be admitted that this differentiation
occurred through a variation in the number of plates of the antecedent
which became fixed in the succedent form.

We may now inquire whether this process of plate formation in
the shell of Peridinidae may have been one of the greater and greater
fragmentation of a shell originally consisting of but one or two or of
a few pieces, or by the amalgamation into large plates of an orig-
inally great number of small shell particles. A clue to this is derived
from the phenomenon of exuviation in the very genus, Peridinium, to
which our especial attention will be directed. Only a vegetative
method of reproduction is known in this genus. The protoplasm of
the body eneysts, the original shell is cast off by a process of exuvia-
tion, and directly a new shell is developed in which at first only the
depressions of the girdle and longitudinal groove can be made out.
The first impression of any plate formation which can be discerned
shows a plate pattern which is the same as that of presumably the
older, and at any rate the usual form, but differing in the prominence
and width of the sutures.

Again in Ceratium, in which a form of reproduction by oblique
fission occurs, one-half of the shell is regenerated in each daughter
individual resulting from the process. Here the covering is at first
homogeneous, but presently becomes divided directly into the num-
ber of plates expected for the adult individual and arranged in the
specifically characteristic manner. The succession of genetically re-
lated individuals contained in chains of Ceratium and of Gonyaulax
which are all of the same plate patterns demonstrates the trustworthi-
ness of this method of reproduction in transmitting a given plate
pattern. Moreover, in these chains individuals are not known which
have a great number of small platelets in their shells apparently in
process of merging into the larger plates of the adult shell.

Nor is it to be expected that an organism of this sort in developing
a protecting covering should form first a number of small platelets
on its surface which later might become fused, but rather that as in
diatoms, various algae, ete., a protective film of substance will aceumu-

418 University of Califorma Publications in Zoology [ Vou. 18

late homogeneously on the exterior. This primitive homogeneous
shell seems in the dinoflagellates to have become divided regularly
into a number of plates. .

In view of the great variety of stereoisomeres possible for a given
number of atoms in organic substances, it is not impossible that the
tendeney toward fragmentation of the shell in certain of the genera
of dinoflagellates and the tendency toward retaining the shell in
fairly large component pieces in other genera of the group may be
associated with the composition of different stereoisomeres of the same
protoplasmic organic series in the shell material of these two portions
of the group.

If, then, the progress of the development of shells of varying com-
plexity on the basis of the number of plates of which they are formed
is in the direction from a homogeneous shell to one of a greater and
oreater number of plates, those species, in general, having the smaller
number of plates and particularly the smaller number of rows of
plates should be regarded as the most primitive and generalized and
those showing the greatest development in number of plates and in
number of rows should be considered the most highly specialized in
this respect.

The formation of a large number of plates in a portion of the shell
in which there might have previously been a small number of plates
may be considered to take place by the splitting of a previously exist-
ing single plate into two plates of equal or of unequal size or by the
appearance of a new plate in a gapping area between plates which
may have been pushed apart by some internal pressure, either pro-
cess involving perhaps a rearrangement of the resulting elements
according to quite a new pattern.

We should expect, moreover, that in the history of such a process
for the development of the plates of the shell of dinoflagellates pos-
sibly to see exhibited at some stage in the ontogeny of certain indi-
viduals indications of the progressive division of the skeleton into a
few plates and these into the final number of many plates. No sug-
gestion of this has been recorded so far as we know. However, this
lack of evidence on this point partakes of only a negative value.

It would seem, then, if our analysis be correct for the method by
which plates of the skeleton arise, that a genus in which there are, let
us say, but five precingular plates is more primitive in this respect
than a genus in which the precingular row contains six or seven
plates, and similarly for a comparison of the number of plates in any

1918] Barrows: Skeletal Variations in the Genus Peridinium 419

other of the rows of the skeleton. Correspondingly, a genus in which
a partial row of accessory plates has been interpolated on the dorsum
of either the epitheca or of the hypotheca is higher in the phylo-
genetic series, other things being equal, than a genus in which there
is no such row of accessory plates. It would seem probable, then, that
a genus having, for example, seven plates in the precingular row might
be derived from a form perhaps still represented in a related genus,
having but six plates in this row by the division of one of these plates
into two parts. We shall have need to refer to this suggestion again.

PosstsLE MretruHop For MULTIPLICATION OF PLATES

It is possible, of course, that plate multiplication takes place by
the splitting of a former plate. Without saying that this may not
occur in certain genera it appears from the progressive series of pre-
cingular plates, for example, which can be constructed for the genera
related to Peridinium, that the splitting of a former plate into two
equal or nearly equal plates does not occur, but rather that new
plates arise at first as small skeletal elements either split off from the
corner of a former plate as, perhaps, in the formation of plates 1’ and
7” of Peridinium or that new plates arise to fill the gap left by a
bulging of the internal protoplasm of the organism which would
cause three plates to be pulled apart at their point of articulation.
That is, the strain which causes the formation of a new plate seems
to require the construction of a new skeletal element rather than a
remolding of a formerly existing element. These elements, the plates,
moreover, seem to be limited in size, and it is probably the impossi-
bility of a shell of one piece to contain the active and growing organ-
ism which has caused the production of a shell composed of a number
of plates. Physical factors of the skeletal material or of the shape of
the organism may determine a limit beyond which the skeletal material
cannot exist as a single plate, the actual area of each plate as well as
its shape depending upon its location. In the few cases where very
large plates are found, as on the dorsal side of the epitheca of
P. excentricum, such excessively large plates are in regions where
there is but little change in shape or contour. In such a region as
the apex, where the contour changes sharply, there are usually found
a number of plates. However, in those forms in which there is found
a protracted apical horn the apical plates are narrow transversely in
the direction of sharp change of contour, but elongated axially in the

420 University of California Publications in Zoology [ Vou. 18

direction along the horn in which the change in contour is shght and
gradual.

In other genera, however, such as Pyrophacus and Gonyaulax, con-
ditions are present which suggest the possible splitting of plates into
subequal portions, due to internal strains. In both of these genera,
but more especially in Pyrophacus, the number of apical plates varies
greatly among the several species of the given genus. In the apical
regions in Pyrophacus a cluster of as many as fourteen plates may be
found irregularly arranged and not to be clearly traced in rows.

In this same connection it is also of interest to note that in differ-
ent genera it is different regions of the shell which are variable, sug-
gesting possibly a difference in the nature of the initial force influ-
encing the change as well as a difference in the location of the point
of yielding to these strains. Thus in Pyrophacus the yielding seems
to occur in the apical region, while in Peridinium the alterations seem
to involve a swelling of the cireumference. This circumferential en-
largement involves a readjustment between previously existing apical
and cingular plates and the stretching apart of these two rows at
some place. This separation seems to occur on the dorsal side of the
epitheeca rather than on the ventral side, and if the organism were
oriented horizontally this might be described as a dorsal humping of
the body with an anterior concavity in the hump. To meet this strain
and to cover the area which would otherwise be left vacant by the
stretching apart of the apical and precingular rows of plates on the
dorsal side, the dorsal epitheeal accessory plates are formed. Once
having been established the strains seem to have been satisfied for
most members of the genus by the introduction of but three such
plates.

We are also interested in a peculiar manifestation of the polarity
of these organisms. The hypotheca in these forms is consistently
more conservative than the epitheeca in regard to the multiplication
of plates. The number of plates in the hypotheca is usually less than
the number in the epitheca and never exceeds this number. We do
not find in the genus immediately under consideration nor in related
genera the evidences of reconstruction or rearrangement of plates in
the hypotheea which we find in the epitheca. On the other hand there
are certain modifications of the hypotheca, but these are not of the
character to be caused by internal forces, but rather seem to be im-
pressed upon the organism by the environment. Thus the develop-
ment of hollow antapical horns is supposed to be due, partly at least,

1918] Barrows: Skeletal Variations in the Genus Peridinium 421

to an attempt at adustment of buoyancy to density in flotation or to
the imparting of a spiral method of locomotion, making rectilinear
progression possible, or to such an upsetting of the body of the dino-
flagellate as it falls through the water as to bring it to present as
great an area as possible to the direction of falling and thus to reduce
the rate of falling by increasing the amount of resistance of the water
to the falling body. Solid antapical horns may also serve some of these
same purposes or be coupled with the function of locomotion in some-
what the same way as the lists on the margins of transverse and longi-
tudinal grooves are related to the activity of the flagella by confining
the currents of water set up by the flagella.

Thus it seems to be the epitheca, or the anterior end of the organ-
ism. which reflects the active internal forces of the organism and the
hypotheca, which possibly reflects certain superficial modifications
stimulated more directly by the environment. This conclusion is
somewhat in accord with the theory of gradients recently put forward
by C. M. Child, according to which we should expect the rate of meta-
bolism to be higher in the anterior than in the posterior end of organ-
isms, and hence the initiative for profound morphologic modification
more pronounced here than in the posterior region.

The number of sides of each polygonal plate of the skeleton varies
in this genus from three to six, the more common number being five.
Only the plates 1” and 7” in species of Paraperidinium and plate 1”
of Metaperidinium (dextrad) are triangular. These are presumably
plates of rather recent phylogenetic origin. Hence a triangular shape
is believed to be an undeveloped or primitive condition in the history
of a plate.

The reticulated surface markings also enclose polygonal areas,
bounded by straight or nearly straight sides, among which there are
found comparatively few triangular areas, the areas being usually
five- or six-sided. However, none of these plates or reticulated areas
is equilateral or symmetrical. This condition is in contrast to the
frequent condition in other animals of repeated hexagonal elements, in
which the elements are nearly if not quite regular, such as the omma-
tidia of a compound arthropod eye, the comb cells of a bee hive, and
the framework of the skeleton of many Radiolaria.

There is every indication that not only the formation of plates.in
the shell but also the size of these plates is a matter of internal regula-
tion. This appears from the circumstance that after ecdysis the shell
is reformed with plates presumably in the original pattern. While

422 University of California Publications in Zoology [ Vou. 18

observations have not followed every step of exuviation and regenera-
tion of the shell under controlled conditions, it is presumed that the
plate arrangements of the shell ordinarily are not changed during
this eedysis unless unusual environmental changes are encountered.
The uniformity of the plate pattern in chains of individuals found for

Giseaeaseaa
NIGEREA
TALL TV ACLA |

SEERA
QASHDesachPeSESRGhhSe oO
SAPSIS7ET AY ah 2. ay aes
BESBRSeaea BSE a

Hera

PEE EEE EEE PEPE EPP EEE EEE EE EEE Ee Pee Ps

Fic. 18.—Chart of measurements of critical sutures of the dorsal epithecal
plate patterns for 44 and 46 specimens of Peridinium divergens Ehrbg., 1.e.,
for the sutures between plates la and 4” on the left and 3a and 4” on the right.

1918] Barrows: Skeletal Variations in the Genus Peridinium 423

certain species of Ceratium and Gonyaulax strengthens this conclusion.
Further, the fact that plates rarely exceed a certain maximum size,
and then only in the case of fairly flat portions of the shell, suggests
the existence of some factor either within the organism itself or within
the material of the shell which makes for a fragmentation of the shell
into plates of a restricted size.

REGIONS OF SKELETAL VARIATION IN Peridinium

We are now, perhaps, in position to apply these observations to
members of the genus, Peridinium. Aside from variations in the
plates of the ventral area which are imperfectly known because of
the great difficulty in analyzing them there are no variations in plate
articulations of the hypotheea within this genus. The _ principal
morphologic variations concern the development of antapical horns,
and as has been pointed out above, these cannot be regarded as of pre-
dominating significance. There is, however, variation not only in the
number of plates of the epitheca but also much variation in the
arrangement of the number of epithecal plates (14) which is of most
frequent occurrence. These variations are found to occur in two
general regions; one, on the ventral side of the epitheea on either hand
of the rhomboid plate (1’), and the other on the dorsal side between
the articulation of the partial row of three (in typical cases) acces-
sory plates, presumably of recent phylogenetic origin, and the mid-
dorsal precingular plate (4). There is, however, a considerable
number of species in which the partial row of accessory dorsal plates
contains only two plates instead of three, the greatest number devel-
oped in this row in this genus. These species, as recorded, however,
all have the same ventral plate patterns. The variations in the
vicinity of the mid-dorsal precingular plate (4) are such as might
be expected to accommodate the smaller number of accessory plates
present.

The regions in which these articulations change will be seen from
the accompanying diagram (fig. 19) of an apical view of Peridinium
divergens Ehrbg., showing all of the epithecal plates in this, a typical
species of this genus.

It is to be noted that there are only four points of the intersection
of sutures between plates at which changes in articulations occur.
These four points are paired symmetrically with respect to the sagittal
plane, and changes of articulation seem usually, though not always,

424 University of California Publications in Zoology [ Von. 18

to occur coincidently in two dorsal regions, while the two ventral
regions of change seem often to vary independently of each other. The
changes occurring at the two pairs of variable regions have been dia-
grammed in figs. 1 to 8. Fig. 3 shows an asymmetrical ventral plate
pattern, which is formed by the non-coincident variation of the pair
of ventral regions of variation in the reverse order from that of fig. 2.

It is to be noted- that figs. 1 and 4a show the only possible com-
binations of the plates of this part of the epitheca if the two sym-
metrically opposite regions of variation behave coincidently. But a
stage represented by fig. 2 must have occurred in the formation of the
stage given in fig. 4a, unless that of fig. 4a arose by direct symmetrical
progression from the stage given in fig. 1, which, as has been ex-
plained, is presumed to represent the primitive condition for these
plates in this genus. This stage shown in fig. 2, however, has not been
found by the writer in any specimen, and if we may except the figure
of Claparéde and Lachman (1859, pl. 18, fig. 26), which may have
been drawn from the inside of the shell, or from the dorsal side, in-
stead of in correct orientation, this pattern has not been figured in
literature.

The variations of the dorsal region involve the possibilities for
the articulation of plates about the anterior right and left corners of
the mid-dorsal precingular plate, with readjustment on the part of
the adjacent accessory plates (la, 2a, and 3a) and also of the abutting
precingular plates (3’ and 5’).

It will be noted that in each of the regions which undergo varia-
tion there are only four plates the rearrangement of which is involved
in changing from one pattern to the other; that in this quartette of
plates it is the diagonally opposite pairs of plates which are either
separated or brought into juxtaposition with each other; that only
two patterns are possible for each quartette in a given variable
region; that one of these patterns must therefore be regarded as the
alternate of the other; that the patterns change by the obliteration of
the suture between two plates about to be separated in forming the
hew pattern, and by the formation of a new suture at right angles
to the one just obliterated through the newly affected contact of the
alternate pair of plates.

With one exception all possible combinations for these plates in
this pair of variable regions are known, and are presented in figs. 1
to 8. It may be repeated, then, that in the most fully developed
presumably the most characteristic, and certainly the most abundantly

1918] Barrows: Skeletal Variations in the Genus Peridinium 425

Fig. 19.—Diagrams of the arrangement of plates in a typical member of
the genus Peridinium, P. divergens Ehrbg., for the epitheca (upper figure) and
for the hypotheca (lower figure). The epithecal plate pattern is that of the
subgenus Metaperidinium, primary division.

426 University of Califorma Publications in Zoology [ Vox. 18

represented portion of this genus, both in species and in individuals,
in which there are fourteen epithecal plates, variations in the pat-
tern of articulations occur at only four points, and especially that,
with the exception of one possible combination of the plates of the
ventral region which is as yet unknown, cases have been found illus-
trating all of the combinations of the plates at each of these four
regions which are geometrically possible.

Among specimens examined or among species already figured in
literature, examples have been found of all of the possible combina-
tions between figs. 1, 3, and 4 for the ventral patterns and figs. 5 and
6 for the dorsal patterns. The series of known combinations of the
dorsal patterns given in figs. 7 and 8 with the three ventral patterns
is incomplete, and from evidence which will be introduced later it
seems that the patterns of figs. 7 and 8 may represent aberrant forms
or forms in which there may have been special attempts at adjust-
ment with unusual conditions of the environment.

PLATE PATTERNS, A BASIS FOR SUBDIVISION OF THE GENUS,
Peridinium

The fundamental importance of the skeleton in portraying phylo-
genetic relationships has already been discussed. On this basis we
venture to propose that the system of patterns outlined above presents
a means for not only accurately describing the species of this genus
but also for relating them more or less closely according to a natural
order.

Superficially it might be possible to divide the genus into groups
either according to the three known patterns for the ventral plates or
into four groups according to the dorsal patterns represented, and to
subdivide these primary divisions according to the several combina-
tions found between these two sets of patterns. There are certain con-
siderations, however, which make it seem reasonable to regard the
variations of the ventral plates as of more fundamental significance
than the variations of the dorsal plates.

In genera apparently related rather closely to Peridiniwm there
are two ways in which the number of plates is increased. These
genera all possess four whorls of plates—apical, precingular, post-
cingular, and antapical. The simplest method for inereasing the
number of plates—and this increase seems to be the trend of special-

>

ld

1918] Barrows: Skeletal Variations in the Genus Peridinium 427

ization and of evolution in this eroup—is by the formation of new
plates in the row already represented. This method is known to
have been carried to considerable development, for instance in such
forms as Pyrophacus, in which the plate formula is 4 (to 12)’—0?—9
(to 12)’-8-9 (to 12)’’’"-0-3 (to 5)’. Another method for in-
creasing the number of plates which must involve a greater readjust-
ment of the skeleton is by the addition of what is to become either
the anterior or posterior accessory row of plates. Such plates usually
make their appearance on the dorsal side of either the epitheca or of
the hypotheea. In other genera we do not find this method resorted
to until the precingular and postecingular rows have broken up into
at least five plates each, and in many genera not until six or seven
plates have been formed in these rows. It would therefore seem that
the increase of the number of plates to a certain point in the cingular
rows is a phenomenon generally prior to occurrence to increase by
the addition of an accessory partially complete row, and that increase
of plates in an existing row is a simpler and less highly specialized
process than the addition of a new row of plates. It seems reasonable
to suppose, therefore, that the changes in the ventral plate pattern
in the genus, Peridinium, are of more fundamental significance than
changes in the dorsal pattern.

Moreover, in certain genera closely related to Peridinium there is
a suggestion that the increase in number of precingular plates comes
from the addition of a new plate at one of the ends of this row on
the ventral side near the longitudinal groove. Thus in Gonyaulax,
plate 6” is very small. A plate introduced at the end of the pre-
eingular row of a form ancestral to the genus, Peridinium, with its
seven precingular plates will probably be small in size in the early
stages after its appearance, but as this new plate increases in size to
match approximately the size of the other plates of the row it will
more and more nearly approach plate 4’ of the preexisting apical row.
Thus in the early stages of the introduction of such plates at either
end of the ventral row the ventral plate pattern on the side of the
rhomboid plate would be represented by the pattern shown in fig. 1.
A later stage representing the full growth in size of one of these
plates would be represented in fig. 3, and if growth should take place
to the same degree on both sides of the rhomboid plate a pattern sim-
ilar to that of fig. 4a would result. Of the three ventral patterns
known, therefore, that of fig. 1 seems to be the more primitive and
that of fig. 4a the more highly specialized.

428 Unversity of California Publications in Zoology [ VoL. 18

There seems, then, to be a broad and sound basis for the division
of the genus into the two groups, Orthoperidinium and Metaperi-
dintum, which Joergensen has defined, and quite as good ground for
giving his group Paraperidinium correlative standing. We would,
therefore, suggest that these names be preserved in common usage
for these three subgenera of the genus, Peridinium.

SUBDIVISIONS OF THE GENUS, Peridinium

It is possible, therefore, to divide the whole genus, Peridinium,
into three subgenera upon a basis which is not only of practical conven-
ience in diagnosis but which also has a natural significance. It might
be possible in some or all of these subdivisions to carry the classifica-
tion according to this system even farther on the basis of the com-
binations which a given plate pattern might form with the known
dorsal patterns. Certainly the characters next in value after the dorsal
pattern would be the characters of type of horn, general shape, surface
markings, ete.

Of the four dorsal patterns figured, only the first two (figs. 5 and
6) occur extensively. Combinations are known between each of these
- and each of the three known ventral plate patterns. The two remain-
ing dorsal plate patterns as shown in figs. 7 and 8, are known to be
combined with one of more of the three ventral patterns.

Upon our interpretation of these ventral plate patterns and the
significance of the series, the group to which Joergensen has given the
name, Paraperidinum, becomes the first one to be considered, as prob-
ably representing the most primitive condition in which the plates 1”
and 7” at either end of the precingular series are of relatively small
size, presumably having been recently introduced. Joergensen’s
eroup, Metaperidinium, represents an intermediate asymmetrical
stage. To distinguish this form from the possible inverse asymmetri-
eal pattern of fig. 2, which is unknown in reality, it may be called
Metaperidimum (dextrad), and the unknown form, Metaperidiniwm
sinistrad.

Joergensen’s subgenus, Orthoperidinium, becomes, then, the most
highly specialized subdivision of the genus.

Paraperidinium.—tT aking up first the known forms presenting
combinations of the plate pattern of Paraperidinium with the sym-
metrical dorsal plate pattern of fig. 5 we may name the following

1918] Barrows: Skeletal Variations in the Genus Peridiniwm 429

species as included in the primary group, Paraperidinium. Species
presenting the dorsal plate pattern of fig. 6 might be termed as con-
stituting a group of Paraperidinium secondary.

P. ovatum Pouchet P. tristylum Stein
(Fauré-Fremiet, 1908, p. 219, (Stein, 1883, pl. 9, figs. 15 and
fig. 5) 16)
P. cerasus Pauls. (Broch, 1910, p. 187, fig. 5)

(Meunier, 1910, pl. 2, fig. 27)

These species have not been found by the writer but two instances
of what otherwise was clearly P. divergens Ehrbg. have been found in
which the ventral pattern of Paraperidinium was present. Mangin
(1911, pl. 7, figs. 10 and 13) has also figured P. divergens Ehrbe. in
which this unusual pattern has occurred.

A specimen taken to have been derived from a race of P. ocean-
cum Vanh. from Sausalito, California, also shows the ventral plate
pattern of Paraperidiniwm with the primary dorsal plate pattern of
fig. 5. This combination in this case is explained as due to unusual
physical conditions of Sausalito Bay, which have, so to speak, de-
formed this species characteristic of the open sea.

Species of Paraperidinium bearing the dorsal plate pattern of
fig. 6 and which may be considered as constituting a group of Para-
peridinium secondary, include :

P. pallidum Ost. P. pellucidum (Berg) var. acutum
(Broch, 1910, p. 45, fig. 17) Ink ae
P. islandicum Pauls. (Fauré-Fremiet, 1908, p. 221,
(Broch, 1910, p. 46, fig. 20) fig. 7)
(Paulsen, 1904, p. 23, fig. 7) P. spinosum, Schiller
P. pellucidum (Bergh) Schutt (Schiller, 1911, p. 3, fig. 3)
(Paulsen, 1908, p. 49, fig. 62) P. curvipes, Ostf.
P. pellucidum (Bergh) var. cras- (Paulsen, 1911, p. 308, fig. 6)
sum FE. F. P. rectum Kofoid.
(Fauré-Fremiet, 1908, p. 220, (Pavillard, 1916, p. 40, fiom)
fig. 6) En

This combination has been confirmed in a number of specimens
of P. pellucidum found by the writer.

The only example which we have met of a combination of the
ventral pattern of Paraperidiniwm with one of the asymmetrical
dorsal patterns is a figure by Paulsen (1907, p. 15, fig. 18) for
P. granii Pauls., which agrees well enough with the general concept
for P. granii in other respects, though specimens of this species which
we have seen from Yes Bay, Alaska, carry the ventral plate pattern
of Metaperidinium with the asymmetrical right oblique dorsal pattern.

430 University of California Publications in Zoology [ Vou. 18

Metaperidinium.—Under Metaperidinium, which may be ealled
Metaperidinium (dextrad) for those species in which the growth of
the girdle plates has proceeded unequally and more rapidly on the
right side of the organism than on its left, we find combinations with
both of the symmetrical dorsal patterns, primary and secondary, and
also a combination of this ventral pattern with the asymmetrical
dorsal pattern of fig. 7, which may be designated as constituting the
group of Metaperidinium (dextrad), dorsally right oblique.

Under the group of Metaperidinium (dextrad) primary, we find
the following species:

P. divergens Ehrbg. P. globulus Stein
(Stems 188s repli, LOy en 2F (Broch, 1910, p. 182, fig. 2, IT)
supported by numerous ob- P. monacanthus Broch
servations of the writer) (Broch, 1910, p. 150, fig. 25)
P. adriaticum Broch P. brevipes Pauls.
(Broch, 1910) p. 192), fig. 8; Tt (Paulsen, 1911, p. 313, fig. 13)
and III; probably a variety P. breve, Pauls.
of P. divergens) (Broch, 1910, p. 47, fig. 21)
P. crassipes Kofoid forma typica P. wiesneri Schiller
Broch | (Schiller, 1911, p. 2, fig. 2)
(Broch, 1910, p. 53, fig. 27) P. lenticulatum F. F.
(Broch, 1910, p. 194, fig. 9) (Fauré-Fremiet, 1908, p. 217,
P. crassipes, forma autumnalis fig. +)
Broch P. curvipes Ost.
(Broch, 1910, fig. 10, IIT) (Broch, 1910, p. 48, figs. 10,
P. quarnerense (Schroder) Broch 12, and 13)
(Broch, 1910, p. 184, fig. 3) (Pavillard, 1916, p. 35, fig. 8)

Only one reliable instance of the occurrence of the secondary
dorsal plate pattern in Metaperidinium is at hand. P. rosewm Pauls.
(Paulsen, 1904, p. 23, fig. 9).

Specimens showing an unequal development of the end plates of
the precingular row but in a reverse order from that found in Meta-
peridinium (dextrad), and hence to be held for the group which may
be known as Metaperidinium (sinistrad) if represented, are as yet
unknown, if we may except a doubtful figure by Claparéde and Lach-
mann.

At least two eases are reported of the combination of the ventral
plate pattern of Metaperidinium (dextrad) with an asymmetrical
dorsal pattern, that which we have termed the dorsally right oblique
pattern, shown in fig. 7. These are:

P.-mite Pav. P. steinii Joerg.
(Pavillard, 1916, p. 37, fig. 9) (Kofoid, 1909, pl. 2, figs. 1, 5,
and 7)

(Broch, 1910, p. 185, fig. 4)

1918] Barrows: Skeletal Variations in the Genus Peridinium 431

Perfectly definite examples of a form attributed to P. granw have
been found in collections in which the ventral plate pattern of Meta-
peridimum is combined with the dorsally left oblique asymmetrical
pattern; and similar specimens, presumably of a- form of P. granii
also, have been taken from Union Bay, Alaska, showing the dorsally
right oblique asymmetrical pattern.

Orthoperidinium.—In the subgenus, Orthoperidinium, the fol-
lowing species are found with the primary dorsal plate pattern, shown
in fig, 5:

P. oceanicum Van H. P. conicum (Gran) O. and 8.
(Stein, 1883, pl. 10, fig. 1) (Paulsen, 1908, p. 59, fig. 74)

P. claudicans Paulsen (Gran, 1902, p. 189, fig. 14)
(pl. 3,- figs. 1 and 2) P. obtusum Karsten

P. depressum Bail. (Fauré-Fremiet, 1908, p. 223,
(Broch, 1910, p. 51, fig. 26) fig. 9)

P. parallelum Broch
(Broch, 1906, p. 153, fig. 4)

Forms presenting the ventral plate pattern of Orthoperidinium
and the secondary dorsal plate pattern shown in fig. 6 are:

P, tabulatum Ehrenberg P. typus Bergh
(Entz, 1904, fig. 7, a, b) (Fauré-Fremiet, 1908, p. 222,
(Schilling, 1892, pl. 3, figs. 21a, fig. 8)
b) P. cinctum Ehrenberg
P. bipes Stein (Bachmann, 1911, pl. 6, fig. 7)
(Stein, 1883, pl. 11, figs. 7 P. conicoides Pauls.
and 8) (Paulsen, 1905, p. 1, fig. 2)
(Schilling, 1891, pl. 3, figs. P. faeroénse Pauls.
23a, b) (Paulsen, 1905, p. 5, fig. 5)
P. leonis Pay. P. obtusum Karsten
(Pavillard, 1916, p. 33, fig. 6) (Karsten, 1906, pl. 23, figs.
P. pentagonum Gran 12b, ¢)
(Gran, 1902, p. 191, fig. 15) P. subinermis Pauls.
(Paulsen, 1908, p. 59, fig. 76) (Paulsen, 1907, p. 19, fig. 26)
P. anthonyit F. F. P. willei Huitf.-Kaas., (fresh-
(Fauré-Fremiet, 1908, p. 216, water )
fig. 3) (Schilling, 1913, p. 45, fig. 0)

P. westii Lemm. (freshwater)
(Schilling, 1913, p. 47, fig. 0)

Only one example has been found in literature in which the ven-
tral plate pattern of Orthoperidinium has been combined with that
of an asymmetrical dorsal plate pattern, in this case that termed the
right oblique. This appears in P. punctulatum Pauls. (Paulsen,
1907, p. 19, fig. 28). This combination has also been found by the
writer in a collection from Sausalito, California, in a specimen which

432 University of California Publications in Zoology [| Vou. 18

in all other respects except that of the dorsal plate pattern corre-
sponds with the usual concept for P. claudicans (see pl. 19, figs. 1
and 2).

In addition to these examples just quoted there are a number of
other species which a lberal interpretation of the definition of the
genus, Peridimum, would include. In all of these additional species,
however, the number of dorsal accessory plates is less than three,
usually two. These forms also all fall into the group, Orthoperi-
dinium and, strangely enough, they are, many of them, inhabitants
of fresh water. In most of these forms the two accessory plates are
symmetrically placed but may be grouped either as shown in figs. 10,
11, or 12. These figures represent all the possible ways in which two
accessory plates could be interpolated among the preéxisting plates.

Only one species is definitely reported as having the two accessory
plates arranged as in fig. 10:

P. quadridens Stein (freshwater)

(Stein, 1883, pl. 11, figs. 4, 5,

and 6)
(Schilling, 1913, p. 38, fig. 41)

Among the species having the two accessory plates arranged as in

fig. 11 are:
P. umbonatum Stein (freshwater ) P. achromaticum (Lev.) (fresh-
(Stein, 1883, pl. 12, figs. 2, 4, water )
and 6) (Ostenfeld, 1908, pl. 5, figs.
(Schilling, 1891, figs. 25a 42-43)
and b) (Schilling, 1913, p. 44, fig. 50)
P. trochoideum (Stein) Lemm. P. marchicum Lemm. var. java-
(Lemmermann, 1910, p. 336, nicum Wol. (freshwater)
figs. 33-36) (Woloszynska, 1912, p. 702, fig.
P. pusillum (Pen.) (freshwater) 25)
(Schilling, 1913, p. 41, fig. 45) (Schilling, 1913, p. 42, fig. 47)

Among the species having the arrangement of-the two dorsal
accessory plates as shown in fig. 12 are:

P. laeve Huitf.-Kaas (freshwater ) P. thorianum Pauls.
(Huitfeld-Kaas, 1900, pl. ? (Paulsen, 1905, p. 1, fig. 1)
fig. 3) P. monospinum Pauls.
P. aciculiferum Lemm. (fresh- (Paulsen, 1907, p. 12, fig. 11)
water ) P. latum Pauls.
(Schilling, 1913, p. 39, fig. 42) (Paulsen, 1908, p. 41, fig. 48)
P. multipunctatum F. F. P. minutum Kofoid
(Fauré-Fremiet, 1908, p. 227, (Kofoid, 1907, pl. 30, figs. 42—

fig. 12) 43)

1918] Barrows: Skeletal Variations in the Genus Peridinium 433

Beside the species just enumerated as having dorsal plate pat-
terns of figs. 10, 11, and 12, which are fairly symmetrical, there are
at least three species in which the two dorsal accessory plates are dis-
posed of in a very asymmetrical pattern:

P. excentricum Pauls. P. perrieri Fauré-Fremiet
(Pavillard, 1916, p. 31, fig. 4) (Fauré-Fremiet, 1908, p. 228,
P. paulsent Mangin fig. 14)

(Mangin, 1912, p. 226, fig. 12)

A single report is extant of a species of Peridinium without any
anterior dorsal accessory plates. This is P. umbonatum var. elpati-
ewskyt Ost. (Ostenfeld, 1907, pl. 9, figs. 9, 10a, and b). The plate
arrangement in this case is that of fig. 9. Although attributed to the
genus, Peridimum, it is doubtful whether, because lacking all acces-
sory plates, this form should not be transferred to another genus.
No report is known to the writer of the occurrence of a species of
Peridinium with one accessory plate.

Special Considerations.—These lists could doubtless be enlarged
by a more complete comparison of published figures and descriptions
with material from dinoflagellate collections, were such always ob-
tainable. The instances which are given here are taken from the fig-
ures which have been drawn with sufficient clearness to serve in this
analysis or from the species the plate patterns of which have been
confirmed or completed from observations by the writer. These
species selected for mention also represent all the possible categories
of plate pattern, ventral and dorsal, and the possible combinations
between these patterns as completely as are known.

It is thus seen that all the six possible combinations between each
of the two dorsal symmetrical plate patterns are represented by one
or more, usually several species. The ventral plate pattern of the
subgenus, Paraperidinium, is known also in combination, but probably
as a sport, with one of the asymmetrical dorsal plate patterns, that
termed dorsally right oblique. The group Metaperidimum (dextrad)
is known in combination, regularly or exceptionally, with examples of
both of the asymmetrical dorsal plate patterns; and the group included
in Orthoperidinium is known, through a single report, in combination
with one of the asymmetrical dorsal plate patterns, that termed dor-
sally right oblique.

The fact that we find the only species having but two dorsal acces-
sory plates in the group, Orthoperidiniwm, which, it seems, must be

434 University of Californa Publications in Zoology [ Vor. 18

the most highly specialized of the three divisions of the genus, Peridi-
nium, is further support for the suggestion that the modifications of
‘the ventral plate pattern are of more fundamental significance than
the interpolation of the dorsal accessory plates, because the develop-
ment of the ventral plate patterns seem to have been able, at least
in certain races of Orthoperidinium, to run through its full course
before the addition of the third accessory plate.

Supporting also the view that the increase in number of the pre-
cingular plates comes from the addition of a new plate, at first small,
at one end of this row near the rhomboid plate is the case of P. minu-
tum Kofoid var. tatihouensis Fauré-Fremiet (1908, p. 227, fig. 13) in
which there is at the right hand end of the precingular row a very
small plate, the eighth in this row. In this species there are still but
two dorsal accessory plates, and these are arranged as in fig. 12. The
ventral plate pattern is, moreover, that of Orthoperidinium.

The group, Orthoperidinium, presents itself to us, perhaps, as a
portion of the genus which because of its high specialization is in a
condition of depletion in a manner ‘‘running out’’ and groping
about in a desperate fashion for some combination of its parts which
may again render it stable. It seems to be a portion of the genus
which is ‘‘fraying out.’’ This suggestion is all the more emphasized
by the large number of irregular and unusually asymmetrical forms
which it contains. In addition to those already mentioned in which
the accessory plates are reduced to two in number, usually symmetri.
cally placed, other forms such as P.. marsonii Lemm. may be men-
tioned in which the structural system in this part of the genus seems
to have broken down even more completely and all traces of sym-
metry in the arrangement of the epithecal plates have been lost.

Summary of Changes of Plate Pattern within a Species—Among
the figures in literature and among the observations of the writer
several cases have come to light illustrating what is apparently
a change in plate pattern within a given species; that is to say, the
plate patterns found in two individuals are different while all the
other characters agree to such an extent as to compel placing these
forms in the same species.

1. P. ovatum Pouchet has been reported by Fauré-Fremiet (1908,
p. 219, fig. 5) with an arrangement of ventral plates according to a
pattern which Joergensen (1912) later termed that of Paraperdi-
nium, and with the primary symmetrical dorsal plate pattern which
is illustrated in fig. 5 of this paper; and again by Broch (1910, pp. 40

1918] Barrows: Skeletal Variations in the Genus Peridinium 435

and 41, figs. 9 and 10) with the ventral plate pattern of Joergensen’s
subgenus Metaperidiniwm.

2. P. granw Pauls. has been figured by Paulsen (1907, p. 15,
fig. 18) with the ventral plate patterns of Paraperidinium and the
asymmetrical right oblique dorsal pattern of fig. 7. What is presum-
ably this same species has been found in Sausalito Bay, California,
with the Metaperidinium pattern for the ventral plates and with the
asymmetrical left oblique dorsal pattern of fig. 8; and in still a third
condition with the right oblique dorsal plate pattern and pattern of
Metaperidinium for the ventral plates in forms from Union Bay,
Alaska (pl. 17, figs. 1 and 2; and pl. 18, figs. 3 and 4).

3. P. claudicans Pauls. is usually found with the ventral plate
pattern of Orthoperidinium and the primary symmetrical dorsal plate
pattern of fig. 5. However, specimens from Sausalito, California, pre-
sent a dorsal pattern of the right oblique type (fig. 7, pl. 19, figs. 5
and 6).

4. In the same Sausalito collection as that just referred to was
also found a specimen of what was probably a deformed race of
P. oceanicum Van H., which was remarkable in displaying the ventral
epithecal plate pattern of the subgenus Paraperidimum instead of the
usual pattern for P. oceancum Van H., that of Orthoperidimum
(pl. 20, figs. 7 and 8).

5. The species P. divergens Ehrbg. is usually found with the
ventral plate pattern of Metaperidinium and the primary symmetri-
cal plate pattern of fig. 5. Two specimens out of sixty-three exam-
ined by the writer have been found with a ventral plate pattern of
Paraperidinium, and this combination has also been figured by Mangin
(1910, pl. 7, figs. 10 and 13).

Summary of Skeletal Relationships——We are dealing then with
the skeleton, the most permanent of the structures of this organism,
but a structure which undergoes certain modification even in the life
of the individual. From genus to genus within the family, Peridi-
nidae, we find this skeleton undergoing variations in regard to the
number of its plates. We find that in this family the number of
plates is increased first by additions in one or another of four funda-
mental rows. In this progressive increase in number of plates the
antapical row usually contains the least number of plates, often
not more than two. The apical row contains more plates than the
antapical but usually fewer plates than either of the cingular rows.
Of these cingular rows it is the precingular in which the number of

436 Umversity of California Publications. in Zoology [ Vou. 18

plates seems to increase most rapidly, and the latest additions to this
row seem to be produced by the addition of plates, small in size at
first, on the ventral side at either end of the precingular row and next
to the rhomboid plate, which must be considered as belonging to the
apical row but which interrupts the precingular row on account of its
extent from the apex to the girdle.

At a certain stage in the progressive multiplication of the plates
of this shell in this family, an accessory plate or an incomplete row
of plates makes its appearance either on the dorsal side of the hypo-
theca between the antapical and posteingular rows or more often on
the dorsal side of the epitheca between the apical and precingular
rows. The number of plates in the postcingular accessory row rarely
exceeds two in number and that in the anterior accessory row rarely
exceeds three in number.

The genus, Peridinium, by definition, perhaps largely fortuitous
or conventional in its formation, is made to include forms having a
definite number of plates in the four main rows, no posterior acces-
sory plate and either two or three anterior accessory plates. In the
greater number of known species coming under this general defini-
tion there are three anterior accessory plates arranged continuously
in a row over the dorsal part of the epitheca between the apical and
precingular rows. Those species in which the number of accessory
plates is less than three are readily related to the major part of the
group. This reduced number of accessory plates is to be regarded
as a preliminary condition introductory to the later condition of three
such plates represented in the greater portion of the genus, or as of
secondary acquisition due perhaps to more or less of a readjustment
upon transfer to fresh-water conditions from estuarine conditions on
the part of fresh-water forms, most of which present such a reduced
number of accessory plates. For some reason the number of these
accessory plates seems in the majority of the species of this genus to
have become three in number but never to have exceeded this number.
No instance is known to the writer of only one accessory plate, but
at least one form has been reported with no accessory plates, which
nevertheless conforms to the other characters of the definition of this
genus.

1918] Barrows: Skeletal Variations in the Genus Peridinium 437

REGIONS OF VARIATION IN THE SHELL OF Peridinium

Variable Regions—We are able to recognize in the Peridinium
shell only four general regions in which the number of skeletal plates,
so fundamental a character in this group, is undergoing change, and
these regions are significant in being closely related to the phylogeny
within the family to which this genus belongs.

These areas of skeletal variation are in the region of the two
opposite ends of the precingular row of plates, which is interrupted
by the long rhomboid plate of the apical row, and in the region ot
the recentiy acquired incomplete row of these dorsal accessory plates.

In the greater part of the genus, that characterized by having
three dorsal accessory plates, there is then a constant number of plates
and there are only four regions in which rearrangement of these
plates seems to take place. More particularly these four places, in
which the rearrangement of plates is known to occur, may be regarded
as two pairs of variable regions, and both of these pairs of regions
occur on the epitheca, for no plate variations are known in this genus
on the hypotheea except within the longitudinal groove, and these are
undoubtedly not of correlative importance with the variations of the
major plates of the skeleton.

On the epitheca we are then dealing on the ventral surface with
variations involving the size of plates 1’ and 7” and with alterna-
tions in plate pattern where the anterior apices of these plates articu-
late with the adjacent plates, 7.e., for plate 1’” with plates 2”, 1’ and 2’,
and for plate 7” with plates 6”, 1’, and 4’.

In addition to the evidence of the clear progressive development
of this line of variation in plate number in genera related to Peridi-
nium and of the comparison of the small size of these plates 1” and 7”
in the most closely related genera, we find that in Peridinium these
plates vary in size and that the plate patterns or patterns of the
sutures of articulation vary in this region as may be necessary
according to the size of these two plates.

That these variations in plate pattern are not due to varying size
of the rhomboid plate, plate 1’, is evident because of the nearly uni-
form proportion in size which this plate maintains in relation to
adjacent plates throughout most of the species of this large genus.
In no species is the rhomboid plate known to expand to the unusual

438 University of California Publications in Zoology [ Vou. 18

degree necessary to meet plates 2” or 6” without the growth, which
is unknown, of these plates to meet it half way. On the other hand,
it is easy to see how plates 1” and 7”, beginning, as it were, as small
plates, budded off from plates 2’” and 6” when these latter were the
end plates of the precingular row and may by increasing in size have
inserted themselves between plates 1’ and 2” on the left hand for
plate 1” and between plates 1’ and 6” on the right hand for plate 7”
until this primary articulation is completely destroyed and plate 1”
has come to meet broadly plate 2’,.and plate 7” to meet plate 4’. We
have thus before us the ventral plate patterns of the known stages
for the three subdivisions of this genus proposed by Joergensen.
First is that of Paraperidinium represented by our fig. 1 in which
there is only a small precingular plate at each end of the precingular
row adjacent to the rhomboid plate. A stage preliminary to this may
be found in Gonyaulax, for example, in which but one such small
plate, that of the right hand, has as yet split off. It is significant to
note also that this plate first seems to split off on the right hand end
at the beginning of this series of development and that later in the
series it is found that the right side proceeds more rapidly in devel-
opment than the left side, which seems to lag, while one stage of
development on the left side seems in present faunas not to be repre-
sented at all. Secondly, the plate pattern of Metaperidinium is that
in which the precingular end plate on the right side has increased in
size until it meets plate 4’, completely separating plates 1’ and 6”.
The corresponding asymmetrical stage in which the precingular plate
on the left end has increased rather than that on the right end seems
not to be known. Finally, we find the pattern represented in Ortho-
peridinium in which both the end plates of the precingular row have
increased uniformly, or if one pleases to so regard it, in which plate 1’.
on the left, has caught up with the maximum development of plate 7”
which can be permitted by the pressure of surrounding plates or by
its own capacity to hold together.

Turning now to the dorsal surface of the epitheca, we find that in
that portion of the genus having three accessory plates the variations
in plate pattern occur in a pair of regions at or near the anterior
corners of the mid-dorsal precingular plate, 4’. Among possible
explanations for the variation of the suture pattern at these points,
we may note that these variations may be due to the increasing size of
the mid-dorsal precingular plate, 4’, so as to crowd the middle acces-
sory plate and effect an articulation with the lateral accessory plates

1918] Barrows: Skeletal Variations in the Genus Peridinium 439

which did not obtain in the primary. condition. This explanation,
however, seems improbable, since in all other related genera there is
no suggestion that this mid-dorsal plate undergoes a great develop-
ment in advance of its fellows in the precingular row.

That the mid-dorsal precingular plate does vary somewhat more
than its neighboring precingular plates, however, appears from the
fact that in those specimens having a small middle accessory plate
with the plate pattern of fig. 5, the mid-dorsal precingular, 4’, occu-
pies a greater are of the equatorial circumference of the organism
than in those species in which the middle accessory plate is large with
the pattern of fig. 6. There seems, then, to reside in the mid-dorsal
precingular plate, 4”, some capacity for variation in relative size
from species to species, though there are other considerations to sug-
gest that the major stimulus for a real change in plate pattern may
take effect in the middle accessory plate just anterior to it. More-
over, since it is probable that the accessory row of plates is of the
more recent introduction, phylogenetically, in the skeleton of Peridi-
nium, it seems probable also that these plates are in a more plastic
condition than the plates of previously existing rows.

It seems, then, that we may consider only the probability that the
seat of alteration of dorsal plate patterns lies among these lately intro-
duced plates of the accessory row. If so, is the center of expansion
by which articulations are changed, seated in the middle accessory
plate or symmetrically in the lateral accessory plates or in all these
plates of the accessory row? Upon regarding the proportionate size
of each of these three plates to the adjacent plates of the skeleton, it
appears that among the species illustrating the changes in dorsal pat-
tern the middle accessory plate varies more widely than the lateral
accessory plates relatively to the size of the adjacent plates, while the
lateral accessory plates undergo but comparatively slight variation in
size. It seems probable, then, that in the part of this genus contain-
ing these accessory plates it is the middle one which is the more plastic
or the more variable.

Origin of the Accessory Plates——Of peculiar significance just here
is the absence of any example of a single accessory plate in this genus.
The accessory plates which first appear, do so as a pair, apparently
in response to a stimulus applied symmetrically on the anterior dorsal
region, and it is in connection with the symmetrical effect of this stim-
ulus for the interpolation of an accessory row of plates that the sig-
nificance of the absence of any form displaying a single accessory

440 Umversity of California Publications in Zoology | Vou. 18

plate lies. This pair may appear in one of two ways: either, appar-
ently as an increase in the number of apical plates from four to six
by the addition of two new plates arising at the dorsal corners of
apical plates 2’ and 4’.. These may have increased in size until they
reached the apex (as shown in fig. 10) and come to simulate apical
plates, though really of secondary origin. This arrangement of plates
is illustrated by very few species. If these accessory plates, however,
arose from the posterior corners of apical plate 3’, their increase in
size may at first have produced the arrangement of plates given in
fig. 11, and later that of fig. 12. Examples of all of these patterns
have just been mentioned (see p. 410). At this stage, however,
a single unpaired plate may have made its appearance just posterior
to the junction of the two newly developed accessory plates shown in
fig. 12, v.e., at the anterior point of the mid-dorsal precingular plate
of this figure, or just anterior to the junction of the two accessory
plates at the posterior corner of the mid-dorsal apical plate (3’).

Here, then, are two lines of development suggested for the intro-
duction of the accessory plates. The first, that shown in fig. 10, seems
to have permitted no further progress, while the second, that illus-
trated in figs. 11 and 12, seems to have been that leading to such an
arrangement of plates as is shown in fig. 5, and found in a large num-
ber of species of this genus. This in turn by increasing growth of
the middle accessory plate probably led to the arrangement of plates
shown in fig. 6, also frequently found among species of Peridiniwm.

The absence of a single unpaired accessory plate need not be re-
garded, however, as out of harmony with the occurrence of single
accessory plates described for such genera as Ceratocorys, Spiraulaz,
and Heterodinium, since the accessory plates in these genera occur
asymmetrically and in Ceratocorys not at all in the same region as in
Peridinium. Moreover, the occurrence in Peridinium of two accessory
plates together, as in the first instance, may be but the complete sym-
metrical progression of the same sort of development which produced
but a single such plate on the right shoulder of Spiraulax or Hetero-
dinium, and we may yet expect to find a similar asymmetrical Peri-
dinitum caused by some aberration or partial inhibition in its normal
development, unless in fact one of these other genera may itself
represent this asymmetrical stage.

It is doubtful, however, from which plate or plates these two acces-
sory plates may have come. The fact that in many other species the
mid-dorsal precingular plate, 4’” seems to possess a certain plasticity

1918] Barrows: Skeletal Variations in the Genus Peridinium 441

‘suggests that these two accessory plates may have been budded off

from the anterior corners of that plate (4). The subsequent bud-
ding off of a third and median plate from the now single and median
corner of the mid-dorsal accessory plate, 4’, or from the posterior
corner of the mid-dorsal apical plate, 3’, would provide the third
accessory plate, found characteristically in this genus.

On the other hand, the occurrence of such a species as P. quadri-
dens, in which there are apparently six apical plates, two of which may,
however, be interpreted as accessories, suggests that the two lateral
accessories may have arisen from buds from the two lateral apical
plates, 2’ and 4’. These plates would have forced what was originally
the mid-dorsal apical plate, 3’, into the future position of the middle
accessory plate, and a bud from the anterior corner of this plate may
have formed another plate to take the place of the mid-dorsal apical
plate just removed. The varied articulations of the mid-dorsal acces-
sory plate, 2a, do not make clear, however, the manner by which these
variations can be connected with this method of origin, and we are
inclined, on the whole, to favor the hypothesis that the two lateral
accessory plates arose in the region of the anterior lateral corners of
the mid-dorsal precingular plate, 4’.

The middle accessory plate may have originated in one of at least
two ways; either as a bud from the anterior corner of the mid-dorsal
precingular plate, now projecting more or less between the two lateral
accessory plates already formed, or the middle accessory plate may
have been formed from a bud from the posterior corner of the middle
apical plate, 3’. This latter suggestion seems most readily to fit in
with the subsequent development of the middle accessory plate and
the readjustment of the lateral accessory and other plates due to its
enlargement. In the absence of definite evidence to suggest a contrary
view, we are inclined to favor the origin of the middle accessory plate
from a different source than that from which the lateral accessory
plates may have come, and probably from the region of the anterior
median corner of the mid-dorsal precingular plate secondarily after
the formation of the lateral accessory plates (la and 3a).

Evidently the forms produced in these early stages, if this hypothe-
sis be correct, were not stable, and evolution seems to have proceeded
at once to the formation of more fully specialized forms having three
well-developed accessory plates. In this condition the genus seems to
have settled down into approximate equilibrium and durability. Spe-
cies illustrating fully all of the early stages through which this pro-

442 University of California Publications in Zoology [ VoL. 18

cess of evolution may have passed, by showing many different sizes
of the accessory plates, seem now to be lacking, possibly having per-
ished as unsuited for some reason to the conditions under which they
would have been compelled to live. These conditions, in fact, them-
selves changing, may have been the stimulating cause for this series
of steps in the development of this genus. Though now missing from
our peridinian fauna as at present known, it is not impossible, how-
ever, that under certain conditions which might upset the equilibrium
of species which find their way into bays, brackish areas, etc., rever-
sions to or repetitions of the early stages of this development may ocea-
sionally be found.

Be the origin of the accessory plates as it may, we find the
greater portion of the genus characterized by having three accessory
plates, with at least four patterns for the arrangement of the constant
number of plates in this general mid-dorsal region of the epitheca.
two symmetrical patterns and two asymmetrical.

Origin of the Principal Symmetrical Dorsal Plate Patterns —In
this portion of the genus we may suppose, then, that at a stage
shortly after the development of the third discreet accessory plate this
plate became of approximately the same size as the two lateral acces-
sory plates. At this stage the plate pattern would be that of fig. 5,
the middle accessory plate having met the anterior edge of the mid-
dorsal precingular plate, 4’’, and flattened out against a considerable
portion of the anterior margin of this plate.

By a continuation of skeletal growth in this region of the shell,
which seems to be one of plasticity because of the recent introduction
in this region of these additional plates, plate 2a, the middle accessory
plate, may be presumed to have continued to increase in size. At any
rate, this plate is found to vary in proportionate size as compared
with adjacent plates.

When of its smallest size the middle accessory plate presents to-
gether with the adjacent plates the pattern of fig. 5, which is charac-
teristic of such forms as P. divergens Ehrbg., P. crassipes Kofoid, and
P. oceanicum Van H. When of a larger size it seems to have spread
still farther along the anterior edge of the mid-dorsal precingular
plate, 4’’, and to have intruded itself between the former articulations
of plates la and 4” on the left and plates 3a and 4” on the right sep-
arating these plates entirely and reaching to plate 3” on the left and
to plate 5” on the right, presenting the plate pattern of fig. 6, one
which is characteristic, for example, of P. conicwm (Gran) O. and §.,

1918] Barrows: Skeletal Variations in the Genus Peridinium 443

P. islandicum Pauls. and P. tabulatwm Ehrbg. These are the two
dorsal plate patterns most frequently found in this genus.

Origin of the Asymmetrical Dorsal Plate Pattern.—Aside from
patterns caused by a reduced number of plates, there are, however,
two other patterns which are occasionally represented, and, curiously
enough, usually among forms taken from bays or sounds or regions
in which the regularity of the physical conditions of the open sea are
somewhat interfered with or altered. These two patterns are asym-
metrical and are caused apparently by the greater development of one
side, or of one lower or posterior corner of either plate 2a or 4’... We
have assumed that the initiative for these readjustments lies in the
region of the posterior corners of plate 2a as the newest skeletal mem-
ber of a presumably plastic portion of the shell rather than in plate 4’.
which forms part of a phylogenetically much older portion of the
shell, although the shape and to some extent the size of plate 4’” seem
to be more or less altered, conversely to plate 2a, to meet its changes.

By the development of the posterior left corner of plate 2a the
7
the more common of these two asymmetrical patterns. It will be seen
to be a combination of the patterns of figs. 5 and 6, and has been
found by Miss Bathgate in San Francisco Bay material as well as by
the writer (pl. 19, figs. 5 and 6).

By the greater development of the posterior right hand corner of

pattern of fig. 7 is formed and this in the experience of the writer is

plate 2a the pattern of fig. 8 is formed. This pattern has been figured
by Joergensen (1902, p. 7).

There are, of course, other explanations which can be given for
the origin of these several dorsal patterns. The two skew or asym-
metrical patterns may have been’ formed by a sliding of the row of
accessory plates over the row of precingular plates because of some
foree, probably internal, which may have pushed the whole row over.
This suggestion, however, seems rather improbable because it attempts
to account for the formation of the skew patterns on a hypothesis
separate and of a different order from any upon which the original
formation of these plates can be accounted for, and also because no
other adjustments of surrounding plates are to be noted, as would be
expected from a readjustment so great as the shifting of the position
of three plates in so prominent a position as that in which the acces-
sory plates are. ;

Summary of Discussion of Dorsal Patterns.—It seems, then, that
the accessory plates appear first in the genus as a symmetrical pair

444 University of California Publications in Zoology [ Vou. 18

and that later a third plate is added between them, making the num-
ber three characterstic of the greater part of the genus. Upon the
changes of articulation of this middle accessory plate, 2a, are rung
four changes of plate pattern, depending largely upon the degree of
growth and symmetry of growth of this plate. Under the symmetrical
development of the plate the patterns of figs. 5 and 6 only are pro-
duced. By the unequal development of what are apparently a pair
of centers of change, either pattern of figs. 7 or 8 is produced. These
latter patterns appear under conditions of unusual modifications of
the environment, and these changes in pattern involve the articulations
of plates in the vicinity of the anterior corners of the mid-dorsal pre-
cingular plate, 4”.

The presence, however, of the two skew patterns, the reverse of
each other, shows that a double center of variation or a pair of vari-
able areas are involved, and that, whereas in the majority of cases
the development in these two centers proceeds at a uniform rate,
there are cases in which for some reason this balance is upset, one
center developing more rapidly than that on the opposite side, pro-
ducing as a result the asymmetrical dorsal plate patterns of figs. 7
and 8.

PAIRED AREAS OF CHANGE OF PLATE PATTERNS

The fact is striking that there are on the ventral and also on the
dorsal surfaces of the skeleton of the epitheca paired areas of change
of plate pattern which seem to be due to some internal stresses which
at first seem to have made for the production of additional plates in
the history of the forerunners or early members of the genus and
which later seem to have manifested themselves in modifying the
arrangement of a constant number of plates.

The pair of variable ventral areas present coincident modifications
in two subgenera of the genus, Paraperidinium and Orthoperidinium,
but may vary independently of each other, as is shown in Metaperv-
dinium. Strangely enough, a fourth group to be represented by the
reverse asymmetrical pattern from that of Metaperidinium seems not
to be found in our present fauna. Its absence, however, is to be re-
garded as of only negative significance.

Similarly, the variable dorsal areas usually develop coincidently,
but under certain circumstances behave individually. It may be

1918] Barrows: Skeletal Variations in the Genus Peridinium 445

noted that whereas the asymmetrical ventral pattern is known in a
widely distributed portion of the genus represented in all seas, the
asymmetrical dorsal patterns are found usually, except for such a
form as P. steinvi Joerg., in specimens which have come from a region
of more or less modified environment from that of the high seas or
open coast, and also that the dorsal asymmetry, among species re-
ported, seems to be the more often produced by growth upon the left
side of the middle accessory plate than upon the right side. As evi-
denced in Metaperidiniwm, it is on the right side, however, that devel-
opment seems to proceed the more rapidly, and forms having a devel-
opment of the newly acquired precingular plate, which is more rapid
on the left side than on the right are unknown.

Here there are apparently four potentially independent charac-
ters, which, however, more often than not, behave in dorsal and ven-
tral pairs.

A second important consideration is that there is apparently no
particular connection between the dorsal and ventral pairs and, as
will be shown later, a full set of combinations is known between both
symmetrical patterns of the ventral side and the symmetrical patterns
of the dorsal side, and a number of the possible combinations of these
patterns with the asymmetrical patterns of both ventral and dorsal
sides are also known.

It seems not impossible also that the character of a pair of horns
on the hypotheea, which may or may not be developed to approxi-
mately the same degree, may be correlated with the influence making
for the frequent pairing of the right and left characters of plate vari-
ation. Also, the initial occurrence of a pair of dorsal anterior acces-
sory plates symmetrically placed, instead of a single accessory plate
upon perhaps the left shoulder, as in Heterodimiwm, is of particular
significance in connection with the occurrence of these other features
in pairs by emphasizing the fundamental and natural condition of
bilateral symmetry in this genus. If this be related here as elsewhere
to a method of rectilinear locomotion, it is suggestive of the super-
sedence of a structural response to locomotion of this sort over the
structural response suggested in the torsion of the shell by the addi-
tion of but a single accessory plate in other genera as a concomitant of
the spiral method of locomotion and the oblique strains set up by this

method.

446 University of California Publications in Zoology [ VoL. 18

COMPLETENESS OF THE SERIES OF VARIATIONS

Geometrical Patterns Represented—Another significant fact is
that, given the constant number of plates on the ventral surface of the
epitheca, all possible geometric combinations of these plates are repre-
sented among the species of this genus, except for the unknown group
which should have the asymmetrical pattern, the reverse of that of
Metaperidinium, and which we may eall Metaperidinium (sinistrad).

Similarly, on the dorsal side, given the constant number of plates
after the full development of three accessory plates, all geometric
combinations possible about the pair of dorsal regions of variability
are known.

This complete series of combinations makes it possible to suggest
the manner by which these changes in plate pattern occurred and
confirms our confidence in the hypothesis suggested for the sequence of
these changes. The completeness of this series of combinations also
suggests the great individuality of each region of variability as a
character capable of variation independent, at times at least, of all
of the other similar characters of change; and again, the great extent
to which this group of organisms seems to have expanded, occupying
all avenues of variation possible with a given structure.

Completeness of Combinations of Patterns——Dealhng first with the
symmetrical patterns, both ventral and dorsal, we find that species
are known representing combinations of the symmetrical ventral pat-
terns of both of the subgenera, Paraperidinium and Orthoperidimium,
with both of the symmetrical dorsal patterns as represented in figs. 5
and 6. The patterns of the subgenus, Metaperidimwm, also are known
in several species in combination with both of the symmetrical dorsal
patterns.

It appears, therefore, that all of the combinations possible, six
in number, between the two symmetrical dorsal plate patterns and
the three known ventral patterns are represented more or less abun-
dantly in the peridinian fauna. This circumstance again confirms
the independence of the characters represented by the different pat-
terns and the wide range of the trials by which nature seems to have
coupled these characters of plate patterns together, and also the success
which combinations of plate arrangement according to the three ven-
tral plate patterns, two of which are symmetrical, with the symmetri-

dorsal pattern.

1918] Barrows: Skeletal Variations in the Genus Peridinium 447

The combinations of the asymmetrical dorsal plate patterns with
the ventral plate patterns are less complete, possibly because less
fully known, and it is to be expected that under certain circumstances
the missing combinations may still be found occasionally, with the
ever-increasing intensity of our examination of this group. At present
the ventral plate pattern of the subgenus, Metaperidinium, is known
to occur in combination with both of the dorsal symmetrical plate
patterns, and at least one instance, in the case of P. punctutatum
Pauls., is known for the combination of the ventral plate pattern of
the subgenus, Orthoperidinium, with the right oblique asymmetrical
dorsal pattern.

That portion of the genus having but two accessory plates is alto-
gether confined to the subgenus, Orthoperidinium. This pair of acces-
sory plates seems to have appeared in two methods: one, that shown in
fig. 10, seems to have been able to proceed no further than this first
stage; the other, shown in fig. 11, with increase in size of this pair of
accessory plates, might have formed a pattern such as that of fig. 12,
from which the full complement of three accessory plates as shown
in figs. 5 and 6 might have developed. All of these combinations of
symmetrical dorsal and ventral figures are known in Orthoperidinium,
and also combinations with various asymmetrical patterns.

The unexpected combination of an early or primitive type of
dorsal pattern, involving but two accessory plates, with a late or
specialized type of ventral pattern, that of the subgenus, Orthoperi-
dinium, may perhaps be explained for some of these species on the
basis that many of these forms are derived from brackish water or
marine progenitors, and having undergone an unusual transition upon
being transferred to a body of fresh water, an intrinsic subordination
of the introduction of dorsal accessory plates to the accession of ven-
tral precingular plates may have become accentuated. The fact that
nearly all freshwater species have the combination of plate patterns
first described may be accounted for upon the basis that species of
the subgenus, Orthoperidinium, are much more common than those of
either of the other subgenera of Peridiniwm, and furnish the more
frequent chance for accidental transfer. In such a form as P. excen-
tricum, having one small and one very large accessory plate, it is not
impossible that a secondary fusion may have occurred between the
middle and right accessory plates.

448 University of California Publications in Zoology [Vou. 18

VARIATIONS IN THE LENGTH OF CRITICAL SUTURES

Further light upon the manner of change of plate pattern may
come from an examination of the varying length of the sutures in
these variable areas, particularly of those sutures which drop out and
of those new ones which are formed in the transposition from one
plate pattern to the next. It will be recalled that the dorsal plate
pattern of P. divergens Ehrbg. is that of fig. 5. The only known
symmetrical change in this pattern involves the obliteration of the
suture lines between plates la and 4” and plates 3a and 4” by the
enlargement of plate 2a so as to establish articulation expressed by
the sutures between plates 2a and 3” and plates 2a and 5’. In a long
series of personal observations and from an examination of published
figures of P. divergéns, the writer is not aware that this typical dorsal
plate pattern for P. divergens is ever altered in this species. Measure-
ments of these critical sutures, between plates la and 4” and plates 3a
and 4” have been made for a total of forty-four specimens taken at
random in groups of from six to eleven specimens from each of six
regions: Yes Bay, Alaska; two localities in the vicinity of San Diego,
California; from Christineberg in the Skagerak; from Cette on the
Mediterranean; and from Naples. The results of these measure-
ments are expressed in the accompanying chart (fig. 17), which shows
that the range of variation for the length of this suture is from .0405
to .1810 of the transdiameter with a double crested norm with maxima
at .07 and .09. It is to be noted that in no one of these instances
measured did the length of this suture fall below .04 of the transdiam-
eter of the specimen.

The length of the corresponding suture between plates 3a and 4”
passes through a somewhat similar range of variation from .0405 to
.2134 of the transdiameter with a double crested norm and maxima at
.06 and .08 and with no measurement less than .04 of the trans-
diameter.

The critical sutures of the variable areas of the ventral side of
the epitheca have also been measured for most of the same specimens
and for a few others, totaling again forty-four specimens, with the
result that the length of the suture between plates 4’ and 7” has been
found to range in this series from .027 to .1101 and in one instance
to .1397 of the transdiameter, with again a double crested norm with
maxima at .05 and .08 (fig. 18).

1918] Barrows: Skeletal Variations in the Genus Peridinium 449

On the opposite side of the rhomboid plate the suture between
plates 1’ and 2” was found to range from .0620 to .2389 and in one
instance to .3221 of the transdiameter, the summation of the measure-
ments of this suture giving a triple crested curve with maxima at .13,
.15, and .17. The lowest maximum is so slightly separated from the
rest of the curve, however, as to be probably of no significance. The
occurrence of two maxima consistently in this analysis seems to be
accidental and is doubtless correlated with the derivation of these
specimens as geographic races from several widely separated sources,
though the cause for the double crested curve is not directly apparent
eveh upon examining suture measurements for the specimens from
each region. The crests are separated in a given curve by only two
units of measurement on the ordinate axis, and such a segregation
may be due to the reduction of the measurements for plotting to the
nearest integral number of hundredths of the length of the transdiam-
eter of the organism.

It is to be noted that the length of the suture between plates 4’
and 7” and plates 1’ and 2” in no ease fell below .027 of the trans-
diameter and that the length of the suture between plates 1’ and 2”
did not fall below .0617. In this connection a further observation is
of peculiar significance. In a longer series of specimens of P. diver-
gens, sixty-three in number, observed by the writer, two specimens
were found which presented not the usual ventral patterns for
P. divergens but the pattern for the subgenus Paraperidinium. These
specimens were, however, characteristic of P. divergens in all other
respects. Mangin (1911, pl. 7, figs. 10 and 13) also figures two speci-
mens in which the same modification of plate pattern is found in
specimens which must still be assigned to the species P. divergens.

We cannot but infer from these records, therefore, that occasion-
ally the plates of the ventral side of the epitheca of P. divergens
present a plate pattern which, upon the basis proposed for the deriva-
tion of these plates, must be regarded as more primitive than the pat-
tern usually presented by this species in this region. It seems, there-
fore, that occasionally, as if inhibited by some factor, or perhaps if
not stimulated as much as usual, plate 7’ in some specimens does not
grow to its usual size, and does not quite reach plate 4’, nor fully
separate plates 1’ and 6”. Here, then, appears to be a case of certain
instability in respect to this one potentially variable region, involving
not only the minor variations in lengths of sutures, which is to be
expected, but involving also variations in the size of certain plates

450 University of California Publications in Zoology [ Von. 18

usually contiguous—an instability of so great a moment as to produce
a plate pattern very different from that characteristic for the species
in this region. This instability may, moreover, be located largely in a
single plate, 7’’, and the inference goes to support the previous sue-
gestion that plate 7” in Peridinium is of late phylogenetic origin.

In the two specimens of P. divergens figured by Mangin (1911,
pl. 7, figs. 10 and 13), which have an unusual pattern, the critical
sutures are well developed and the pattern is unmistakable. Measure-
ments of the unusual sutures between plates 1’ and 6” give values of
1071 and .1587 of the transdiameter, and measurements of the cor-
responding suture on the left hand of the rhomboid plate, which is of
the normal pattern for this species, give values of .0357 and .1270
of the transverse diameter.

The unusually short length of the suture between plates 1’ and 2”
in one of Mangin’s figures is noteworthy in view of the usual great
length of this suture in most of the specimens of this species measured,
and is suggestive of the profound effect of any influence which would
upset the normal equilibrium of the morphological elements.

These measurements were taken from drawings made to a scale of
1:1500, usually from square ventral or dorsal views. There is, how-
ever, a certain amount of foreshortening in these drawings of sutures
which lie upon curved surfaces that is unavoidable. Instead of mak-
ing an allowance for this foreshortening the sutures have been -mea-
sured just as they have appeared in the drawings. The drawings,
made with camera lucida, are thus projections of the surface of the
organisms which they portray. The general effect upon these measure-
ments is that many of the values given are less than the actual length
of the sutures represented. In no ease is an exaggeration of measure-
ment possible. Any errors from this method of measuring the suture
are, therefore, in favor of the general conclusions which will presently
be drawn in examining the significance of the measurements.

SIGNIFICANCE OF VARIATION IN SUTURE LENGTH

The oceurrence of a few specimens of P. divergens with an unusual
ventral plate pattern is to be regarded as of very great importance.
Of equal importance in this consideration is the occurrence of species
answering the descriptions of P. ovatum, P. claudicans, P. oceanicum,
and P. granw in every respect except that of the plate pattern, and
in this one character presenting plate patterns on either dorsal or

1918] Barrows: Skeletal Variations in the Genus Peridinium 451

ventral aspect, which is foreign to the usual form of the species.
Applying this analysis still further to the case of P. divergens, this
circumstance in the first place demonstrates the plasticity of this region
on the right side of the ventral surface of the epitheca. However,
a greater significance appears from examining the lengths of the
eritical sutures in this region of the shell of P. divergens. In no ease
does the value of the suture between plates 4’ and 7” fall below .04
of the transdiameter in the pattern normal for the species. That
is, these two plates always meet each other for a definite length of
their periphery. The suture separating them always maintains a cer-
tain definite and considerable value. The widening of sutures in
certain specimens, presumably with age, may mask this appearance,
though it is possible to find that the opposed margins of these two
plates always present edges of definite and considerable length and
that the plates never really meet by two points bringing together the
four sutures of their adjacent edges at one intersection point. Nor
in any other instance have more than three sutures been found to
come together at one point. Instances of the apparent meeting of
four sutures at one point upon critical examination show an inter-
vening length of suture between two intersection points of three
sutures each; never do four plates actually come into contact at one
point. Here, then, is the record of forty-four random instances in
which this suture between plates 4’ and 7” varying through a consider-
able range never falls below .03 of the transdiameter.

In contrast to this usual condition, a few instances are known in
_ which an alternate pattern has appeared, the only other pattern pos-
sible by any rearrangement of plates at this point. This alternate
pattern is caused by the failure of plate 7” to meet plate 4’ as usual.
In this alternate and unusual pattern it is, then, the suture between
plates 1’ and 6” which is of critical significance. This suture in the
two exceptional cases figured by Mangin (1911, pl. 7, figs. 10 and 13)
is of considerable length and is not short as though the usual pattern
for the genus had barely slipped over into the alternate pattern. In
two other cases observed by the writer, but unfortunately not recorded
by drawings, this suture between plates 1’ and 6” was also of con-
siderable value.

Turning now to the varying length of the critical sutures in the
three other regions of varying plate pattern in this species, P. diver-
gens, there is not only no suggestion of a merging of the given pattern
for P. divergens with the alternate pattern possible in any of these

452 University of California Publications in Zoology [ Vou. 18

places where changes of plate pattern seem to have occurred in the
formation of other species of the genus, but the value of the critical
suture in each case which must be obliterated in the formation of a
new pattern never quite approaches zero.

On the left hand side of the ventral surface of the epitheca the
critical suture is that between plates 1’ and 2”. In a change to the
Orthoperidinium pattern this suture would be obliterated by the meet-
ing of plates 2’ and 1’’, which in P. divergens are separated. How-
ever, in P. divergens, there is never any suggestion of such an approxi-
mation of plates 2’ and 1” and the suture between plates 1’ and 2”
is always of considerable length.

On the dorsal surface of the epitheca, the plate patterns at the
posterior corners of the middle accessory plate usually are symmetri-
cal in this genus. In P. divergens, although varying through a wide
range of length, the critical sutures between plates la and 4” and
plates 3a and 4”, which must be obliterated in the transposition to
the alternate patterns for these regions, never fall below .04 of the
length of the transdiameter. In the measurement of Broch’s figures
these critical sutures are also found to preserve their definite and
considerable value.

Here there are over 160 measured cases in which the length of the
critical suture in variable regions of the shell of specimens of P. diver-
gens, neluding the alternate unusual pattern in one of the variable
regions for two of the instances, does not approach zero in value, but
maintains a definite and relatively considerable length. This is main-
tained in spite of the fact that other species of this genus are funda-
mentally characterized by having a different plate pattern in these
eritical regions.

Now the significance of this fact seems to be this. Species in this
genus are evidently formed by the rearrangement of a constant num-
ber of plates in a limited number of possible geometric patterns.
There are in this genus only four regions where such adjustments
occur. At each region only two different patterns are possible, one
the alternate of the other. One pattern is changed into the other by
the expansion of one or both of a pair of diagonally opposite plates,
causing the separation of another pair of plates previously in con-
tact and the obliteration of one suture with the establishment of a
new suture.

In specimens of P. divergens examined, the patterns of three of
the four regions of possible variation seem to be stable. The pattern

1918] Barrows: Skeletal Variations in the Genus Peridinium 453

of the fourth variable region, the right hand side of the ventral sur-
face of the epitheca, seems, however, to be unstable and to present occa-
sionally the alternate pattern for this region, unusual in this species.
This particular region seems, therefore, to be in a state of greater
plasticity than any one of the other potentially variable regions.

The essential point in this portion of the discussion of plate varia-
tion in Peridiniwm is that there is no complete series of variations
between the usual pattern and the exceptional pattern found in this
part of the shell of this species. In such a complete series of imper-
ceptible variations the suture between plates 4’ and 7” would become
shorter and shorter and finally disappear, after which disappearance
a new suture between plates 1’ and 6” would gradually take its place.
In the series there would be a stage in which four plates and four
sutures would come together.

Extremes of such a possible series are known, presenting both
alternate plate patterns. Within this species this region is, there-
fore, known to be unusually variable and to present the full gamut
of possibilities of plate arrangement possible, though the plate pat-
tern is usually confined to one type. However, the variation of the
critical suture in this usual plate pattern never approaches beyond a
certain amount the point of obliteration, which must be passed before
the alternate plate pattern can be produced. In a few instances
found of the presence of the alternate plate pattern, the new critical
suture is shown to be of definite and considerable value. No authentic
instance is known of the merging of the two patterns by the meeting
of four plates at one point with the obliteration of the critical sutures
of both patterns. Drawings which seem to show such a condition
may be rejected as not sufficiently accurate to be trusted in a matter
where unprecise observation may make so great a difference as here,
in view of the large number of first hand cases which have been very
critically examined in this regard.

It seems probable, therefore, that when the plate pattern at a
variable region changes within a species or between two different
species, it does so with a jump; that each pattern is characterized
by a certain suture, which varies about its own norm; that these
norms do not merge into one another in each pair of alternate pat-
terns possible at a given point, but that the two patterns are separate ;
and that when the plates do readjust themselves in response to internal
stresses they do so with a certain amount of abruptness without pass-
ing in the process through all of the intervening stages between the
normal proportions of the two patterns.

454 Unversity of California Publications in Zoology [ VoL. 18

There is therefore effected a sort of limited kaleidoscopic move-
ment of the plates upon each other in response to internal stresses
with sufficient remodelling of the margins of the plates to establish
contact sutures of definite and considerable length. This all goes to
support the view that the plates of one pattern are in a state of
equilibrium which requires a certain amount of accumulated strain
before transformation into the alternate pattern can occur; that each
pattern represents a state of approximate equilibrium of the skeletal
elements out of which the plates may be forced only by the aceumula-
tion of an unusual stress sufficient to throw the plates over into an-
other arrangement of equilibrium in the alternate pattern.

The equilibrium of each pattern seems usually to be characteristic
and constant for each species. The abruptness of the transition from
one pattern to another is illustrated in the case of P. divergens just
described. This transition, however, is not accompanied by other
morphological changes sufficient to warrant the description of a new
species. As a rule it may be supposed that changes which would
throw the plate patterns from one relation of equilibrium into another
would also be accompanied by such other structural changes as to
compel the consideration of the new form as a species.

Particularly with the pair of dorsal patterns in P. divergens
Ehrbg. is it to be seen from the curves charted that in the groups of
specimens from each locality the trend of variation of the pattern
on both sides of the organism is much the same in each group, and
the mode for the length of both the right hand and left hand critical
sutures is about the same. This is in accord with the general observa-
tion of the dorsal symmetry of pattern in this genus, to which there
are but few exceptions, some of these occurring under conditions of
an unusual environment which may be presumed to have interfered
with the morphological equilibrium of a species.

The ventral patterns are, however, not so closely coupled as was
noted in defining the subgenera of this genus, Paraperidinium, Meta-
peridinium (dextrad), and Orthoperidinium, on the basis of ventral
plate pattern.

It is presumed that at least one of the specimens figured by Mangin
showing the Paraperidimum pattern does not differ otherwise from
the average run of specimens of P. divergens. The other specimen
differs somewhat in surface markings, but this may be merely an age
difference. These specimens are, therefore, regarded as specimens of
the species, P. divergens, which show an unusual form of plate pattern.

1918] Barrows: Skeletal Variations in the Genus Peridinium 45}

)

From the absence of intervening stages showing the transition
from one pattern to the other; from the fact that in the exceptional
patterns found in Mangin’s figures, these patterns do not at all ap-
proach a transitional condition; from the fact that the critical suture
of this unusual pattern is very long; and from the position of the
mode of variation of length of the critical suture in the typical
divergens pattern with a minimum extreme for the curve for the
length of this suture which does not reach closer than .03 of the trans-
diameter to the vanishing point for this suture, we conclude that the
normal shape for plate 7” in this species carries a truncated anterior
portion where it meets plate 4’; that with a truncation of its anterior
border of a greater or less extent, as represented by the curve of
variation given above, the plate pattern in this region is in a state
of equilibrium; that any force tending to upset this equilibrium
throws the arrangement of plates at once over into the only other
pattern possible, with already a critical suture of considerable length ;
and that a condition of two opposite plates in a pattern meeting at a
point without a truncated margin, and bringing together four suture
lines at one point is an extremely unstable and an unknown condition.

In this connection a discussion of the suture relations of the dorsal
pattern of such a species as P. conicum is apropos because here the
eritical sutures of the pattern, in this case that of fig. 6, are very
short. In fact, the pattern in this region has frequently been figured
as the intersection of four sutures. In a considerable number of speci-
mens of this species which we have examined, however, it has always
been possible to resolve these obscure relationships into the pattern
shown in fig. 6. In no case was found the alternate pattern that is
possible in this region. We regard this cireumstance in P. conicwm as
no different from that observable more clearly in P. divergens and in
other species: that a certain juxtaposition of plates in a given region
effects a condition of stability in the arrangement of these plates with
a certain amount of fluctuating variation in the length of the articula-
tions of the plates of the pattern; that in a transition from one pat-
tern to the alternate a stage of instability is encountered of which
no representatives persist; and that a more or less broadly truncated
juxtaposition of opposite plates of the quartette involved in a pattern
is essential to the establishment of equilibrium. This juxtaposition
manifests itself in presence of the so-called ‘‘critical suture,’’ for
which a mode and extreme limits of variation can be determined.

This method of analysis might be applied to all of the other cases

456 University of California Publications in Zoology [ Vou. 18

cited—P. oceanicum, P. claudicans, P. grant, and P. ovatwm—in
which two plate patterns occur in specimens which must still be re-
garded as belonging to the same species. These rare changes of pat-
tern are always well isolated from the normal pattern characteristic
of the given species. No series of gradations has been observed be-
tween such an unusual pattern and the normal pattern; on the con-
trary, the length of the critical suture for the normal pattern seems to
vary between definitely recognizable extremes, the minimum limit of
which is still well above the vanishing point for the suture. The gen-
ral conclusion from all of these observations is, therefore, that a cer-
tain pattern is characteristic for a given species; that this pattern may
occasionally be changed; but that such changes occur abruptly as
mutations and are without a connecting series of intergradations.

Mutations

We have pointed out here several definite and different arrange-
ments of the plates of the shell of species of Peridinium. These
arrangements presumably represent states of equilibrium between
potentially variable elements. A change in pattern involves the short-
ening of one suture and the introduction of another suture at right
angles to it and between two different plates. However, each suture
maintains its own norm for the fluctuating variations which it may
be expected to undergo, and transitional stages between the two
possible patterns which a given group of plates may assume are
unknown.

Hence, in at least this superficial character of plate pattern, these
organisms undergo mutations which must be recognized as such if we
are to admit any phylogentie sequence at all among these species; that
is, the change from one plate pattern to another requires a certain
saltation to bridge the gap. That such saltations when they have
occurred have remained permanent at least for a time is shown by
the presence of species exhibiting nearly all of the arrangements
of a given group of plates which are geometrically possible. This
character of the plate pattern seems, therefore, to undergo mutations
in the generally accepted meaning of abrupt, discontinuous, morph-
ological changes which reappear in successive generations after their
first occurrence.

The pattern of the sutures is, however, not the real character, but
is dependent upon the size of the plates which the sutures bound. The

1918] Barrows: Skeletal Variations in the Genus Peridinium 457

size of these plates is in turn under control of whatever may be the
factor making for the orderly fragmentation of the shell and the
arrangement of its parts found in this group of organisms. Whether
this fundamental factor for plate growth proceeds by leaps and bounds
or not we cannot determine, because the very material of the shell in
which this factor is expressed may by some physical quality of its own
tend to retain its fragments in a given arrangement until a certain
accumulation of strain may become sufficient to cast it over into another
arrangement in somewhat the same way as the crystals of a kaleido-
scope retain a given pattern even though the barrel of the instrument
be moved through an appreciable are of rotation before falling into
another pattern which in turn retains a certain degree of permanency.

However, so far as the character of the arrangement of the plates
themselves and its expression in suture pattern are concerned, these
certainly behave as mutations. There is no suggestion that the pat-
terns are connected by a series of fluctuating or continuous variations,
but on the contrary, evidence is present that given patterns are not
so connected at all, and that a considerable gap of unknown relations
of the plates concerned remains between the alternate patterns in a
given variable region. This seems to be a perfectly clear and clean
eut result so far as can be Judged from the mass evidence of a general
population. It is to be regretted that the cultural methods of the
protozoan geneticist have not been adapted as yet to this material.

The independent behavior of each of these four variable areas in
certain cases, as well as the coupling of the dorsal and ventral areas in
pairs in certain other cases suggests that in these characters of vary-
ing plate patterns we may be dealing with unit characters in an
unusually simple and discreet form.

PossIBLE INFLUENCE OF THE ENVIRONMENT

There is some evidence to suggest that conditions of the environ-
ment different from those of neritic or pelagic localities where given
species may be ‘‘at home’’ may be responsible for changes in plate
pattern as well as in other characters of dinoflagellates. Thus, for
example, such a form as P. grani is found in embayments such as San
Francisco Bay and Union Bay, Alaska, and particularly in the Baltie
Sea where the salinity is very much lower than in the open ocean. An
even more striking instance comes from the specimens from San Fran-
cisco Bay which undoubtedly are related to P. oceanicum Van H. but

458 University of California Publications in Zoology [ Vo. 18

in which the pattern of Orthoperidinium characteristic of P. oceanicum
in its typical form has given way to the more primitive pattern of
Paraperidinium. This striking reversion is accompanied also by an
abortion of the antapical horns. Other characters, and particularly
the relation of its position in the fauna of the collection in which it
occurred to the general population of the region, leave little doubt
that this particular specimen is a highly modified specimen of the
species P. oceanicum. In San Francisco Bay were taken the specimens
of P. claudicans which display the unusual right oblique dorsal pat-
tern. P. claudicans and P. oceanicum are both species of the open sea,
and it seems highly probable that the altered conditions of salinity,
density, and temperature encountered by those specimens swept into
bays by the tide may have stimulated these departures from the normal
structure of these species.

C. CONCLUSIONS

From this analysis of the morphology of the skeleton of Peridinium
the following conclusions are suggested:

1. A distinct difference is to be pointed out not only in the organ-
ization of the shell in the two principal families of the Dinifera, the
Peridinidae and the Dinophysidae, but also in the manner of develop-
ment followed in each family. In the Dinophysidae the number of
plates remains constant. These four major plates seem to be able to
conform to a great variety of forms of the body without breaking up
into smaller plates. The skeletal variations in this family consist of
differences in the development of such skeletal appendages as the lists
of the girdle and of the longitudinal groove, and also in the degree of
porulation, distribution of pores, and association of pores with other
surface markings.

In the Peridinidae, on the other hand, the skeleton behaves very
differently, and progressive development seems to proceed in an orderly
fashion in the direction of an increase in the number of plates of
which the skeleton consists, as well as in the development of various
features of minor importance, including porulation, surface markings,
and antapical horns. The plates become at once arranged in circum-
ferential rows parallel to the girdle, which is of dominant importance
in the activity of the organism. The family, Peridinidae, is to be
characterized especially by this capacity for a peculiar and orderly
fragmentation of the shell according to a progressive scheme.

1918] Barrows: Skeletal Variations in the Genus Peridinium 459

2. In the elassification of species of Peridinium skeletal characters,
particularly the relationships of the fundamental skeletal elements,
the plates, are of much more real value than the type of antapical

3. The size which these plates in Peridinidae attain is limited, and
is apparently correlated somewhat with the degree of curvature .of
the shell. The dimension of the plate is usually longer in the direction
of slight curvature than it is in the direction of great curvature. In
certain regions, e.g., the middle of the dorsal surface or of the apical
horns in Peridinium, the expansion of a given plate seems to have
become accomodated to the expansion by an extension within limits,
in the direction of expansion, of the plates overlying the expanded
portion of the body, rather than by a shifting of the surrounding
plates to distribute the strain. The direction of expansion, however,
is usually not in the form of a curve.

4. There is evidence to suggest that new plates are added to fill
gaps occurring when the three plates meeting at a given point are
separated by some internal pressure, rather than that new plates are
split off from previously existing plates.

5. At a certain stage among the genera in the part of the family
in which Peridinium belongs, the number of plates in the precingular
row increases so that these plates can no longer reach the apical row
and an accessory row of plates is interpolated on the dorsal side
between the two previously existing rows.

The progress of this increase in the number of the plates in the
precingular row may be traced from such genera as Heterodinium,
Sptraulaz, and Gonyaulax which have six precingular plates (the
plate of the right hand end of this row, 6”, frequently being of small
size), through the several stages of development pointed out in the
three subgenera of Peridinium to such an exceptional form as that
figured by Fauré-Fremiet (1908, p. 227, fig. 138) for P. minutwm
Kofoid var. tatthousensis in which there is apparent an eighth pre-
cingular plate at the right hand end of the row.

6. In Peridinium the first plates to appear in this accessory row
come in as a pair of plates. It is not until a later stage that a third
accessory plate makes its appearance between the original pair. Sub-
sequent changes in the arrangement of the dorsal plates occur over
the spots on the body of the organism at which the two accessory
plates appeared. The addition originally of but a single accessory
plate is unknown.

7. On the ventral surface of the organism additional plates added

460 University of Califorma Publications in Zoology — [Vou. 18

apparently as the end plates of the precingular row are pulled
away from the mid-ventral or rhomboid plate, and hence what are
apparently new plates appear at the ventral median corners of the
previous end plates of the precingular row which come to be plates 2”
and 6” in the genus, Peridinium.

8. Four regions of variability are found in that portion of an
genus, Peridiniwm, characterized by having the full complement of
three accessory plates: two on the ventral surface of the epitheeca on
opposite sides of the rhomboid plate near the location of the appear-
ance of the most recently added precingular plates, and two on the
dorsal surface at opposite corners of the middle accessory and mid-
dorsal precingular plates, near the place where the first two accessory
plates appeared.

9. The two dorsal regions usually vary coincidentally, but the two
ventral regions seem to have varied frequently independently of each
other.

10. The variations in these four variable regions consist in the
rearrangement of four plates which approach each other in each of
these regions. Only two alternate patterns can be found among these
four plates of each region, aside from the conjunction of four plates
at one point—a condition which is unknown. Not more than three
plates come together at one point.

11. There thus become possible four different combinations between
the alternate patterns at the variable areas on the ventral side and four
combinations between the patterns of the variable dorsal areas. Of
these sets of four ventral and four dorsal pattern combinations two
of each are symmetrical and two of each are asymmetrical. Alto-
gether sixteen combinations of plate patterns are possible between all
the dorsal and ventral variations in that portion of the genus having
three accessory plates.

12. Joergensen has suggested a subdivision of the genus, Peri-
dinium, on the basis of the one asymmetrical ventral pattern and the
two symmetrical patterns which are known. The fourth possible
ventral pattern, asymmetrical, is probably unknown. To these sub-
genera he has given the names, Paraperidinium, Metaperidinium, and
Orthoperidinium. Classification on this basis is not only a convenience
but is to be justified upon a natural basis since it seems that in the
progress of plate development through several genera an increase in
the number of plates in the precingular row up to the number of seven
holds priority over the interpolation of accessory plates and hence

1918] Barrows: Skeletal Variations in the Genus Peridinium 461

over modifications of the dorsal plate pattern. The absence from
present authenticated records of an asymmetrical ventral plate pattern,
the reverse of the pattern of the subgenus, Metaperidinium, can only
be given negative significance.

13. Since the end plates in Orthoperidinium are much larger than
in Paraperidinium, the former subdivision of the genus is supposed
to represent a more highly specialized condition in respect to plate
erowth than that of Paraperidinum. Metaperidinium by reason of
the lagging of the growth of the plate at the left end of the precingular
row represents an intermediate stage of specialization.

As might be expected in the more highly specialized portion of
the genus, there are, to judge from published records and figures,
more species in the subgenus, Orthoperidinium, than in both of the
two other subgenera combined, indicating the prolifie diversity of form
in highly specialized stages.

14. Over half of the sixteen possible combinations between all
the dorsal and ventral plate patterns are known, including: all four
of the combinations between the symmetrical ventral patterns, Para-
peridimum and Orthoperidinium, and the two symmetrical dorsal
patterns known; also combinations between one of the two asymme-
trical ventral patterns, Metaperidinium, and both of the symmetrical
as well as both of the asymmetrical dorsal patterns; and the combina-
tion of the ventral plate pattern of Orthoperidinium with the right
oblique (asymmetrical) dorsal pattern, reported for at least one
species. One asymmetrical ventral pattern is wholly unknown and
combinations of the asymmetrical dorsal pattern with Paraperidinium
and Orthoperidinium are also unknown.

15. In that portion of the genus in which there are only two acces-
sory dorsal plates, whether symmetrical or of unequal size, the dorsal
patterns thus formed are known in combination only with the sym-
metrical ventral pattern of Orthoperidinium. No instance is known
of the oecurrence of but a single dorsal aecessory plate in this genus.

Of the species on record, many of those having but two accessory
plates are fresh water forms and most of the fresh water forms have
only two accessory plates. This primitive character for this genus
is, however, coupled with the presence of the specialized ventral plate
pattern of the subgenus, Orthoperidimum. Such an unexpected com-
bination is perhaps to be explained on the hypothesis that the develop-
ment of accessory plates is of secondary importance to the rearrange-
ment of the plates developing about the rhomboid plate after the addi-

462 University of California Publications in Zoology [ Vou. 18

tion of plates 1’ and 7” of this genus. Another factor in this con-
nection may be the small size of most fresh water forms, due perhaps
to the lack of buoyant power of the fresh water which, prohibiting any
great disparity between surface and volume, may set a limit upon
expansion.

16. There are then four variable regions which may vary either
independently of each other or in dorsal or ventral couples and which
may combine their variations with each other in a total of sixteen
possible combinations of which at least nine are represented in the
existing species of this genus.

17. The significance of this complete series of combinations of
approximately symmetrical patterns shows not only the pressure of
the influence for variation and the great extent to which this group
of organisms seems to have expanded in all possible directions of
change, but even more significantly demonstrates the progressive
sequence in which these changes of pattern must have occurred.

18. Each of the symmetrical patterns seems to represent a stage of
stability in this process of progressive change, a period when the
skeletal elements and the forces playing upon them are in a state of
approximate equilibrium. Less frequently do the asymmetrical pat-
terns seem to be so stable, though that of Wetaperidinium for the
ventral plates is found consistently in a considerable number of species.
The asymmetrical patterns of the dorsal side often seem, however, to
be concomitants of extensive changes of the physical condition of the
environment, and do not pervade a great portion of the genus.

19. A significant consideration with respect to the combination
of symmetrical and asymmetrical patterns appears from the correla-
tion of the asymmetrical dorsal patterns only with the asymmetrical
ventral pattern. The principal of symmetry seems to be the control-
ling one in this genus and the species having asymmetrical patterns
are apparently less able, in most cases, to persist than are those having
symmetrical patterns.

The symmetry referred to in examining the various plate patterns

of Peridinium is only an approximate and not a perfect symmetry,
it being apparently a fundamental character of Dinoflagellata that
the body is still more or less asymmetrical. However, in view of the
extreme asymmetry displayed by related genera in the development
of antapical horns and in the position for the introduction of the acces-
sory plates, where these oceur, the approximate symmetry maintained
by the skeletal structures in most of the species of Peridinium attracts
attention.

1918] Barrows: Skeletal Variations in the Genus Peridinium 463.

20. As might be expected in conformity with Child’s law of meta-
bolic gradients, the greatest morphologic activity and tendency for
fundamental change is located in the anterior portion of the shell,
while the posterior portion is conservative and carries modifications
which may be due not so much to an internal stimulus as to more
direct but minor responses to an outside stimulus. It seems probable
that in these organisms, as well as those upon which Child worked,
it is the strong unceasing impact of the environment upon the anterior
end of the organism which has made it the more active and the more
likely to respond with profound morphological modifications.

21. In each varying pattern the suture which marks the juxtaposi-
tion of two of the quartette of plates involved in the given pattern and
which therefore becomes characteristic for that pattern varies about
a mode of its own. Intervening stages of the gradual shortening of
such a suture in a supposed transition to the alternate pattern beyond
the established limits of variation for the suture are unknown. Each
pattern is separate and distinct from its alternate and one pattern
by no means grades into the other. There is, thus, a definite gap
between variations of the alternate members of a pair of plate patterns
at each of the four variable regions, as examined intensively for the
species, P. divergens Ehrbg., and.a similar gap apparent between cer-
tain rare changes in plate pattern observed in four other species.

In the experience of the writer no case has been found in which
four sutures actually meet at one point. Cases which at first sight
appeared as such, upon closer analysis in a favorable position have
been resolved into two junction points of three sutures each separated
by a short suture which is one of the two critical sutures for the pair
of alternate plate patterns possible by the rearrangement of plates in
the given region.

22. Mutations appear in two ways in this genus: (1) by the sud-
den change of plate pattern within a species as found occasionally in
the species just referred to above; and (2) by the introduction of new
plates from time to time in the history of the family to which the
genus, Peridinium, belongs. These new plates become new characters
abruptly introduced, and each passes through a process of develop-
ment, involving enlargement and various adjustments with the ad-
jacent plates of the shell.

23. It seems probable then if the species of this genus are in verity
phylogentically related: that one species arose from a_ previously
existing species by a mutation, involving an abrupt addition of a new

464 Unversity of California Publications in Zoology [ Vou. 18

plate or pair of plates, or involving a sudden rearrangement of the
plates of one or another of the four variable patterns; and that each
pattern with its own mode of variation for the length of its critical
suture marks a settled arrangement of the plates in which they are
for the time being at least in equilibrium.

24. To judge from the constancy of a given pattern in a given
well recognized species, it seems to be usual that an influence suffi-
cient to upset the plate arrangement in one or more of the variable
regions is of sufficient moment to cause other changes also, the sum
total of which would place the organism in quite a new species. That
this is not always the case appears from a few exceptional occurrences
of a change in the ventral plate pattern, without any other morph-
ologic changes which would warrant placing these individuals in
another species.

25. These exceptional cases of unusual changes in the ventral plate
pattern of the species just mentioned are to be regarded as reversions
from a specialized to a more generalized type; that is, these changes
may be due to either an inhibitory factor suppressing the full develop-
ment of the ventral plates usual for the species, or more probably to a
lack of the usual stimulus for growth in plates 1” and 7”, on account
of which a more primitive plate pattern is produced. Any interference
with the normal progress of a race of these organisms seems to result
in an inhibition or retardation of progress and fixation at some phylo-
gentically earlier stage of development, rather than in the stimulation
of new lines of variation. The normal progress of development in this
family is suggestive in certain respects of an orthogenetic mode of
evolution.

26. These changes in plate pattern within a species or between
species are, therefore, to be regarded as mutations, and their signifi-
cance is very great in suggesting the mutationary method of species
formation in this group.

27. The suture or plate pattern is, of course, only a superficial
indication of a deeper seated variable factor governing the orderly
skeletal fragmentation and plate growth characteristic of this family.
The kaleidoscopic readjustment of the plates may be of secondary
importance and may be induced by some physical quality of the
skeletal material which retains its inertia until acted upon by a suffi-
cient accumulation of strain to cast it over into another state of tem-
porary equilibrium. Such a circumstance would, however, even if the
underlying form were more regular in its action, alter the mutationary

1918] Barrows: Skeletal Variations in the Genus Peridinium 465

nature of the superficial character of plate variation. There is no
evidence at all that the fundamental character for plate growth does
not proceed at an even pace.

28. Plate formation in this family seems, therefore, to be the ex-
ternal expression of an internal force which is guided in its expression
by physical properties of the shell material in the formation, accord-
ing to a system consistent for the whole family, of plates limited in
size and guided also by geometrical, i.e., mechanical, limitations in
the arrangement of these plates in certain areas said to be more
‘“plastie’’ than other areas because manifesting the changes induced
by the internal force.

29. There is also some suggestion that it may be the changes
themselves in the environment which indirectly induce certain of
these skeletal changes, since the asymmetrical patterns, especially of
the dorsal side, and the sudden transformation from one pattern to
another usually occur in species found under unusual conditions
of the environment, and in species which often show other features,
such as the abortion of antapical horn, indicating the shock of the
reaction of the organism to an unaccustomed environment.

30. While for species in their natural habitat the skeletal patterns
seem to be on the whole a good and convenient species character as
well as one of sound phylogenetic basis, the occurrence of these occa-
sional sports indicates that it is not an infallible character, especially
in regions where a mixture of water from widely different sources
occurs or some other marked deviation from an accustomed environ-
ment.

31. These conclusions in regard to the mutationary behavior of
these skeletal characters perhaps carry an added interest from the
occurrence of these phenomena in this group of marine Protozoa, liv-
ing under an environment very different in many respects from that
of land plants and animals which have been the usual subjects of vari-
ational studies, contributing perhaps support for the normal occur-
rence of a method of species formation by means of mutations.

32. Though these observations may furnish some information upon
the behavior of the discreet elements of the dinoflagellate skeleton,
they do not contribute definite information upon the process of plate
growth in these organisms. This problem will require a different
method of attack, probably involving the continued observation of
single isolated specimens of dinoflagellates through considerable peri-
ods of time.

466 Unversity of California Publications in Zoology [ Vou. 18

D. BIBLIOGRAPHY

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FAuRE-FREMIET, E.
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HuItFELDT-Kass, H.
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KARSTEN, G.
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1907. Das indische Phytoplankton. Ibid., pp. 220-545, pls. 35-54.

Koro, C. A.

1906. On the significance of the asymmetry in Triposolenia. Univ. Calif.
Publ. Zool., 3, 127-133, 2 figs. in text.

1907a. Reports on the scientific results of the Expedition to the Eastern
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March, 1905, Lieut. Commander L. M. Garrett, U.S. N., command-
ing. IX. New Species of Dinoflagellates. Cambridge, Mass., Bull.
Mus. Comp. Zool. Harv. Coll., 50, 161-208, pls. 1-17, 1 chart.

1907b. Contributions from the laboratory of the Marine Biological Station
of San Diego. XVII. Dinoflagellata of the San Diego Region. IIT.
Descriptions of new species. Univ. Calif. Publ. Zool., 3, 299-317,
pls. 22-33.

1908. Exuviation, autotomy, and regeneration in Ceratium. Ibid., 4, 345-386,
33 figs. in text.

1909. On Peridinium steinii Joerg., with a note on the nomenclature of the
skeleton of the Peridinidae. Arch. Protistenkunde, Jena, 16, 25—
47, 2 pls.

1910b. Significance of certain forms of asymmetry of the dinoflagellates.
Ady. Print, Proce. 7th Int. Zool. Congr., Boston, pp. 928-931.

Koro, C. A. and MICHENER, JOSEPHINE R.
1912a. On the structure and relationships of Dinosphaera palustris (Lemm).
Univ. Calif. Publ. Zool., 11, pp. 21-28.

468 University of California Publications in Zoology [ Vou. 18

1912b. Reports on the Scientific Results of the Expedition to the Eastern
Tropical Pacific, in charge of Alexander Agassiz, by the U. S.
Fish Commission Steamer ‘‘Albatross,’’ from October, 1904, to
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ing. XXIV. A peculiar form of schizogony in Gonyaulax. Cam-
bridge, Mass., Bull. Mus. Comp. Zool., Harv. Coll., 54, 333-351,
2 pls.
LEMMERMANN, E.
1899. Ergebnisse einer Reise nach dem Pacific. (H. Schauinsland, 1896-
97): Planktonalgen. Bremen, Abh. Natw. Ver., 16, 313-398, pls.
1-3.
1910. Beitrage zur Kenntnis der Planktonalgen. XXX. Peridiniwm tro-
choideum (Stein) Lemm. Arch. Hydro.-biol., Stuttgart, 5, 336-
338, 3 figs. in text.

LEVANDER, K. M.

1894. Materialien zur Kenntniss der Wasserfauna in der Umgebung von
Helsingfors mit besonderer Beriicksichtigung der Meeresfauna. I.
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LOHMANN, H.

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McEwen, G. F. ;

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America, deducted from Ekman’s theory of the upwelling of cold
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MANGIN, O.

191la. Modifications de la cuirasse chez quelques péridiniens. Note pré-
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Sci., Paris, 153, 644-649, 2 figs. in text.

191le. Sur l’existence d’individues dextres et sinestres chez certains péri-
diniens. IJbid., 153, 27-32, 5 figs. in text.

MEUNIER, A.

1910. Microplankton des mers de Barents et de Kara. Due d’Orleans Cam-
pagne arctique de 1907 (Bruxelles, Bulens), xviii + 355 pp.,
37 pls.

MINCHIN, E. A.

1912. An introduction to the study of the Protozoa (London, Arnold),

xi -+ 520 pp., 194 figs. in text.
MULLER, J.

1841. Ueber den Bau des Pentacrinus caput medusae. Berlin, Abh. Akad.

Wiss., 1841, 177-248, pls. 1-6.
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1912. The depths of the ocean (London, Maemillan), xx + 831 pp., 10 pls.,

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———

1918] Barrows: Skeletal Variations in the Genus Peridiniwm 469

OKAMURA, K.

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1900. Iagttagelser over overfladevandets temperatur, saltholdighed og
plankton paa islandske og gronlandske skibsrouter i 1899 fore-
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figs. in text.

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SCHILLER, J.

1911. Neue Peridinium-Arten aus der nérdlichen Adria. Oes., Bot. Zs., Wien,

61, 332-335, 3 figs. in text.

470 University of California Publications in Zoology [ Vou. 18

SCHILLING, A. J.
1891. Die Siisswasser-Peridineen. Flora d. allg. Bot. Zeit., 3, 1-87, 3 pls.
1913. ‘‘Dinoflagellatae (Peridinieae) in Pascher’’ Die Sisswasser-Flora
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text.
ScHtrt, F.
1892. Ueber Organisationsverhiltnisse des Plasmaleibes der Peridineen.
Berlin, Sitzber. Akad. Wiss., 1892, pp. 165-172, pl. 1.
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STEIN, F.

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VAN HOFFEN, E.

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W OLOSZYNSKA, J.
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WRIGHT, R. R.
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Station of Canada, 1902-1905. Ann. Rep. Dept. Marine and
Fisheries, Fisheries Branch, Ottawa, 39, 1-18, pls. 1-7.

Be)

a -
pen mn |
if
a

a

EXPLANATION OF PLATES
PLATE 17

Peridinium granii Pauls

Fig. 1. Ventral view of type from Sausalito, California, September 24, 1913.
xX 1500.

Fig. 2. Ventral view of type from Union Bay, Bayne Sound, Alaska, May 14,
1906. X 1500.

[472]

PLATE 18
Peridinium grantvi Pauls

Fig. 3. Dorso-apical view of the same specimen shown in figure 1, plate 17.
x 1500.

Note that the dorsal epithecal plate pattern is that which has been termed
the left oblique pattern. The ventral plate pattern is that of the subgenus,
Metaperidinium.

Fig. 4. Dorso-apical view of the same specimen shown in figure 2, plate 17.
x 1500.

Note that the dorsal epithecal plate is asymmetrical and the reverse of that
found in a similar form from Sausalito, California. The dorsal plate pattern of
the form from Union Bay corresponds to the form of P. granii described by
Paulsen (1908, p. 52, fig. 66) from the Baltic Sea, but the ventral plate pattern
figured for the Baltic Sea is that of the subgenus, Paraperidinium.

[474]

ee

ee ee

PLATE 19
Peridinium claudicans
From Sausalito, California, September 24, 1913

Fig. 5. Ventral view. X 1400.
Fig. 6. Dorsal view. X 1400.

Note that the dorsal epithecal plate pattern is of the asymmetrical type
termed right oblique instead of the usual symmetrical type for this species,
shown in text-figure 5.

[476]

PLATE 20
Peridinium oceanicum Van H.
From Sausalito, California, February 13, 1912
Fig. 7. Ventro-apical view. X 1500.
Fig. 8. Lateral view. X 1500.
Note that the ventral epithecal plate pattern is that of the subgenus, Para-
peridinium, rather than that of the subgenus, Orthoperidinium, usually found in

P. oceanicum. It is possible that this particular specimen may be more closely
related to a race of P. depressum Bail. than to a race of P. oceanicum Vanh.

[478]

UNIV. CALIF. PUBL. ZOOL. VOL. 1/8 [BARROWS] PLATE 20

Fig. 7

Fig. 8

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UNIVERSITY OF CALIFORNIA PUBLICATIONS— (Continued)
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24.
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IN

ZOOLOGY
Vol. 18, No. 16, pp. 479-484, 2 figures in text August 10, 1918

THE SUBCLAVIAN VEIN AND ITS RELATIONS

IN ELASMOBRANCH FISHES |
Le qqnsonian ington
fos

BY
J. FRANK DANIEL

INTRODUCTION

C. F. O’Donoghue (1914) has called attention to the confusion in
the literature on the subscapular and subclavian veins of the elasmo-
branch fishes, and has in a way straightened out the difficulty by show-
ing that the subscapular enters the postcardinal sinus and that the
subclavian, formed by the union of the brachial and lateral abdominal
veins, enters the duct of Cuvier.

In my study of the Elasmobranchs I have been attracted to this
problem, since in different types the subscapular varies in extent and
the subclavian differs greatly as to the relative amount of blood which
it receives. In certain cases the condition in both of these vessels is
as O’Donoghue and T. Jeffrey Parker (1886) have shown for Scylliwm
canicula and Mustelus antarcticus respectively. In these types the sub-
scapular vein enters the postcardinal sinus and therefore none of its
blood passes to the heart by way of the subclavian. In others, how-
ever, the subclavian may receive all of the blood from the whole of
the subscapular system. In still others an intermediate condition may
obtain in which a subscapular vein bridges posteardinal and lateral
abdominal systems, so that blood entering it may go to the heart by
either of these systems, depending upon whether it enter the sub-
scapular dorsally or ventrally.

MATERIAL

As material for study I have had access to Heptanchus (Notorhyn-
chus) maculatus ranging from two to nine feet in length and Squalus
sucklu and Mustelus henlei of about two feet in length.

480 University of California Publications in Zoology [Vou 18

MeEtTHOD

For this study the body was transected two to four inches back of
the pectoral fins, and the anterior segment then cut in sagittal plane
from the tip of the nose to the place of severance of the body. By the
latter cut, right or left halves of the head and pectoral regions may be

Fig. 1. The subclavian vein and its relations, Heptanchus maculatus, lateral
view.

p.C.S.

S.SC.V.

s.Ccl.v. rv.

a a

Fig. 2. The subclavian vein and its relations, Squalus sucklii, lateral view.
br. v., brachial vein; co. v., coracoid vein; d. c., duct of Cuvier; 1. a. v., lateral
abdominal vein; l. c. v., lateral cutaneous vein; p. Cc. S., posteardinal sinus; s.cl.v.,
subclavian vein; s.sc. v., subscapular vein.

1918] Daniel: The Subclavian Vein in Elasmobranch Fishes 481

studied in median view. From such a section the lateral abdominal
and subscapular veins are seen to advantage, and all vessels may be
dissected without great difficulty. When color is needed a starch mass
may be injected into the large brachial vein as it leaves the fin. In
this injection the mass is prevented from running out at the cut ends
of the vessels either by plugging the ends with cotton or by ligature.
After the mass has hardened for two days the material is ready for
dissection.

OBSERVATIONS

The conditions which I have found in Mustelus henlei, are in the
main so much like those given for the Australian form of Mustelus as
not to require refiguring. The subscapular sinus receives the lateral
cutaneous vein and empties into the postcardinal sinus; none of its
blood, therefore, reaches the heart by way of the subclavian vein.
The brachial vein from the pectoral fin joins the lateral abdominal
and the two form the subclavian which enters the duct of Cuvier, but
not in common with the inferior jugular as reported for Scyllium by
O’Donoghue.

In one important respect, however, my observations differ from
those recorded for Mustelus antarcticus and Scylliwm. In addition to,
but separate from the subscapular sinus at the distal part of the
scapular cartilage, there is an abbreviated subscapular vein which
extends along the ventral and posterior margin of the scapula and
enters the brachial vein. In other words the subscapular vein is made
of two distinct components: first, a distal sinusoid around the tip of
the seapular cartilage, which receives the lateral cutanedus vein and
joins the posteardinal sinus, and secondly an abbreviated portion of the
subscapular vein, which as a smaller vessel passes down the postero-
median margin of the scapular cartilage to join the brachial vein.
From this subscapular vein blood enters the duct of Cuvier through
the subclavian vein.

In Heptanchus the subscapular (fig. 1, s. sc. v) begins at the tip of
the scapula as a large sinus, passes unbroken down the entire length
of the postero-medial margin of the scapula and enters the brachial
vein (br.v.) at a place where the latter crosses obliquely over the
shoulder girdle. The principal tributary of the subscapular is the
lateral cutaneous vein (l.c. v.) which receives blood from the skin and
empties it into the dorsal part of the subscapular sinus. But since the

482 University of California Publications in Zoology _—[ Vou. 18

subscapular joins only the brachial vein, and has no relation to the
posteardinal sinus (p. c. s.) all of its blood enters the lateral abdominal
vein (l.av.) and passes by the large subclavian trunk (s. cl. v.)
through the duct of Cuvier (d.c.) to the heart.

A second vessel in Heptanchus joining the lateral abdominal almost
opposite the place of entrance of the brachial vein, should be further
deseribed. This I wish to call the coracoid vein (co. v.) since it passes
downward along the posterior margin of the coracoid cartilage. It
soon leaves the cartilage, however, and passes directly downward
toward the midventral line. In this part of its course it runs in the
tissue lying at the base of the pericardio-peritoneal septum. At the
midventral line it joins a similar vein from the opposite side and is
joined by the ventral cutaneous vein.

From this it is apparent that the condition in Heptanchus differs
radically from that in Mustelus as described by Parker. In Heptanchus
the lateral abdominal is the main stem receiving blood from all of the
lateral vessels associated with the paired fins and their girdles. From
the pectoral fin it is joined by the large brachial; while dorsally from
the girdle it receives the subscapular and its tributary, the lateral
cutaneous; ventrally from the girdle it receives the coracoid and its
tributary, the ventral cutaneous vein.

An extremely interesting condition is found in Squalus suckli
which completely bridges these two extreme types. In it the sub-
scapular (fig. 2, s. sc. v.) is a continuous vein, as in Heptanchus, and
as such belongs to the lateral abdominal system; but dorsally this
vessel comes in contact with and may actually have an opening into
the posteardinal sinus (p.c.s.), so that the subscapular connects the
posteardinal and lateral abdominal (1. a. v.) systems. Since the lateral
cutaneous (l.c.v.) joins the subscapular sinus near the union of the
latter with the postcardinal, blood from the lateral cutaneous after
entering the subscapular might pass dorsally a short distance into the
posteardinal sinus, or ventrally into the lateral abdominal vein. In
other words: if the subscapular vein in Squalus sucklu were not
secondarily connected with the postcardinal sinus, Squalus would be
of the heptanchid type; while on the other hand if that segment of the
subseapular, or any part of it, between the entrance of the lateral
cutaneous and the brachial were dropped out, the subscapular, with
its lateral cutaneous, would be a tributary of the postcardinal, and
hence independent of the lateral abdominal system.

1918] Daniel: The Subclavian Vein in Elasmobranch Fishes 483

Discussion

From the work of Parker and O’Donoghue it is clear that the sub-
clavian vein of Elasmobranchs enters the duct of Cuvier and not the
posteardinal sinus as stated by Rabl (1892). But the character of
the blood which it receives depends in great part on the subscapular
vein and its relations.

I am of the opinion that the lateral abdominal, as is postulated by
the lateral fin-fold theory, should be regarded as the main vessel in
relation to the paired fins. As such it should receive the veins of the
‘paired fins and also of their girdles. This case is realized in Hep-
tanchus where anteriorly the lateral abdominal receives the brachial
from the fin and the subscapular and coracoid veins from the girdle.
Furthermore the subscapular and the coracoid increase the importance
of the lateral abdominal by receiving all of the blood from the lateral
and ventral cutaneous veins.

The finding of Parker for Mustelus and O’Donoghue for Scylliwm,
that the subscapular with its lateral cutaneous tributary empties into
the posteardinal sinus doubtless represents the most usual condition ;
but that this is not universal, and that it is brought about secondarily
has, I think, been shown in the present paper. Whether the post-
cardinal receive any of the blood from the lateral cutaneous depends
upon the subscapular vein. If the subscapular is unbroken and un-
connected with the posteardinal, as in Heptanchus (fig. 1), all of its
blood reaches the heart by way of the lateral abdominal and sub-
elavian. In Squalus (fig. 2) where the subscapular vessel, although
continuous, is secondarily connected to the posteardinal there is a
transition from the more generalized heptanchid type to a more
specialized type like that of Mustelus im which the subscapular is
divided into two parts, a distal sinusoid surounding the tip of the
scapular cartilage, and a proximal more or less abbreviated portion.
In this more specialized case, blood entering the distal part from the
lateral cutaneous vein has but one course open to the heart and that
through the posteardinal sinus.

484 University of California Publications in Zoology [ Vou. 18

LITERATURE CITED
O’DoNOGHUE, C. H.

1914. Notes on the circulatory system of Elasmobranchs. I. The venous
system of the dogfish, Scylliwm canicula. Proc. Zool. Soe. London,
1914, 435-455, plates 1-2, 4 figures in text.

PARKER, T. J.
1866. On the blood vessels of Mustelus antarticus: a contribution to the
morphology of the vascular system in the vertebrata. Phil. Trans.
Roy. Soe. London, 177 (2), 685-732, plates 34-37, 2 figures in text.
RABL, C.

1892, Ueber die Entwickelung des Venensystems der Selachier. Festschr. z.
70. Geburtstag, R. Leuckarts.

RAND, H. W., and ULricy, J. L.

1905. Posterior connections of the lateral vein of skate. Am. Nat., 39,
349-364, 5 figures in text.

RAND, H. W.

1905. The skate as a subject for classes in comparative anatomy; injection
methods. Am. Nat., 39, 365-379, 1 figure in text.

Transmitted May 8, 1918.

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Sete oe 2 SPM AEOR 10-07. -o dF CDEUMALY, bol Ge oa, Ee oe he ee Sop aga
12, Notes on the Spiny Lobster (Panulirus intérruptus) of the California Coast,’

Esterly. Pp. 171-184, 2 figures in text. March, 1916 ooo :

fev i : ie as ‘ton Copepods when Certain Recurring External Conditions are Absent, by -

10

30

2 figures in text, plate 13. October, 1917 0.-ccccco.scccccccceleecctteneetccectoseengeeeones .
12. A Synopsis of the Bats of California, by Hilda Wood Grinnell. Pp. 223-404,
plates 14-24, 24 text. figures.. January 31, 1918 222.0202 22
18. The Pacific Coast Jays of the Genus Aphelocoma, by H. 8. Swarth. Pp.
ot 405-422, -1 figure in text, February. -23, -1918- ono oo Tas
14. Six New "Mammals from the Mohave Desert and zaye Regions of California, S
by Joseph Grinnell. Pp. 423-430. pi
15. Notes on Some Bats from Alaska and pheno Columbia, nde 7aiida Wood

Vol. 18.

UNIVEESITY OF CALIFORNIA PUBLICATIONS—(Continued) _ ‘

8. Osteological Relationships of Three Species of Beavers, by Fr. ‘Harvey. ;
March 1OVT 3s see ee
9. Notes on the Systematic Status of the Toads and Frogs of California, by |

Holden. Pp.-75-114, plates 5-12, 18 text figures.

Charles Lewis Camp. Pp, 115-125, 3-text figures, February, 1917-2... Bl

10,.A. Distributional List: of the Amphibians and Reptiles. of California, by

Joseph Grinnell and Charles Lewis. Camp, Pp. 127-208, 14 figures iy text.

Pi Js bee BO BF ces iaes Pewee age ras Rn arp trio eis Nea dane na A NO Oe MN ey apr eee ASH mn eat
il. A Study of the Rates of the “White-Fronted Goose (Anser albifrons) Occur-.

ting in California, by H. S: Swarth:and Harold C, Bryant. Fp. 209-222,

Grinnell. Pp. 431-433.

: Nos. 14 and 15 in one cover. April, 1918

. Revision of -the- Rodent Genus Aplodontia, by Walter. P.. Taylor.
504, plates 25-29, 16 text figures.
The Subspecies of the Mountain mae pa by J oseph, Grinnell.
515, 3 text figures. May, 1918
Excavations of Burrows. of the Rodent Aplodontia, with Observations on
the Habits of the Animal, by Charles Lewis Camp.
in text. “June, 1918

Index in preparation.
1, Mitosis-in Giardia microti, by William C. Boeck. Pp. 1-26, pista a3

Ser rere et eer ere et

Pp. 505-

ween nn na ben ee nn Rene eee nanan n se nee nee eens sent ennaaneednweeensewewnnasseesewee

2. An Unusual Extension of the Distribution of the Shipworm in San Fran-

cisco Bay, California, by Albert L. Barrows. Pp. 27-43. December, 1917. >
&. Description of Some New Species of Polynoidae from the. Coast of Cali- —

fornia, by Christine Essenberg. Pp, 45-60, plates 23. October, 1917 =...

4. New Species of Amphinomidae from the Pacific Coast, by. Christine Essen-

berg. Pp. 61-74; plates 4-5; October, VOLT 2a at noir pancacasgmmanteqeemscencesesnns

5. Crithidia euryophthalmi, sp. nov., from the Hemipteran Bug, Kurgopntharnas le
convivus Stal, by Irene McCulloch. Pp. 75-88, 35 text figures. ‘Decem-.

11) elas 6 3 oy Pagani ca eons ey ti SE oie en ena nce = Man Crepe ees eee UE as
6. On the Orientation of Erythropsis, by Charles Atwood Kofoid and Olive

Swezy. Pp. 89-102, 12 figures in text. December, 1917 ......0::0..........- ey

7. The Transinission of Nervous Impulses in Relation to’ Locomotion in the
Earthworm, by John F. Bovard. Pp. 103-134, 14 figures in text. January,
1918

8. The Function of the Giant Fibers in Harthworms, by John F. Bovard. - Pp.
135-144, I figure in text. January, 1918. 222 cw ne ng nee eee nen on neces

9A Rapid Method for the Detection of Protozoan Cysts in Mainmalian
Faeces, by William C. Boeck. Pp. 145-149. December, 1917..................

10. The Musculature of Heptanchus maculatus, by Pirie Davidson... Pp. 151- 170,
123 -fieures in-text, “Marets, “1918 2c aoa, cr cart ccnceaecnetrce pissin meee n eeenens

ead ee eiw ec ene ne weenewneec cnn dee sone n ees nnn nseeenaneneen a nesesenned nen dasesacnssorsansssseunsatesanasescsserasessuaasseeesenere

11. The Factors Controlling the Distribution of the Polynoidae of the Pacific e

Coast of North America, by Christine Essenberg. Pp. 171-238, plates 6-8,

Pp. 435-
MAY; VOUS Sea eS eee eng :

Pp, 517-536, 6 figures

Octo- = 3
Wey 10d 2 a a eee eee 3

2 “figures in text.< March, 19185. oie cicero cc ntecenal ie ctieopolemtnnetees
12. Differentials in Behavior of the Two Generations of Salpa. democratica ~ ae
Relative to the Temperature of the Sea, by Ellis L. Michael. Pp. 289-2985 ee at
plates 9-11, 1 figure in text. March, 1918 20... cccecieececesteeenesccteeestennton a Rane es
18. A Quantitative Analysis of the Molluscan Fauna of San Francisco Bay, by ee aes
E. lL. Packard. Pp. 299-336, plates 12-18, 6 figs. in text. April, 1918... .40~ 3
14. The Neuromotor Apparatus of Huplotes patella, by. Harry B. Yocom. Pp.
S37-SOG, “pla bes 14-166 ae a NS ean bse marie ee (In press)
15. The Significance of Skeletal Variations in the Genus Peridinium, by A. L.
Barrows. - Pp. 397-478, plates 17-20, 19 figures in text. June, 1916 ........-... 90 Z 2
16. The-Subclavian Vein and its Relations in Elasmobranch Fishes, by J.
tae ee eg

Frank Daniel, Pp. 479-484, 2 figures in text. August, 1918

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_ ZOOLOGY

Vol. 18, No. 17, pp. 485-507, 3 figures in text \

. J 4, 1919
Vol. 18, No. 18, pp 509-519, 7 figures in text ae a

17. THE CERCARIA OF THE JAPANESE BLOOD
_ FLUKE, SCHISTOSOMA JAPONICUM
KATSURADA

“18. NOTES ON THE EGGS AND MIRACIDIA OF
THE HUMAN SCHISTOSOMES

- BY
WILLIAM W. CORT

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UNIVERSITY OF CALIFORNIA PUBLICATIONS
IN

ZOOLOGY
Vol. 18, No. 17, pp. 485-507, 3 figures in text January 4, 1919

THE CERCARIA OF THE JAPANESE BLOOD
FLUKE, SCHISTOSOMA JAPONICUM
KATSURADA

BY
WILLIAM W. CORT

CONTENTS
PAGE
TEINSR AGP OR IL ei Ses 2h I RS AR ai a A RE rey ems BER A A Sah AE COD ORD AR eR Sent J eer 485
IV te seni ey leeks seer ete ee Pemar ek eee B Laney ed et ee LT ee Pk A Le tN Re Mare uh ee 489
ING EeeR FLA WONG LUBE SINE NG Foie? 2 Re fee Sete pe eh Sen ee ine er a 2 ee ne pre ene 490
Characters soles chishOsoMenCencamiae cesses. owe si neuen Sie soled oe acee 491
SiUCuUTeROIMt Ne mGehG anes set tree ee cet yack dre eben Heel Same ve eee 492
Oralgsnckersandacepiallca.o land sits 2 reese tcte oe ieee ee eee see ee ee 496
ANCETIRGARINY. NORE UELING) (GENCE oe eee pee) es Pn Oe MIE Spe ieee SUELO AEE eed See Ree Ss 502
HT Yj a eas ELT tas sce LES OI it TEA 2 ese a Pte, Sees Matte DIE gE Sa 504
HISTORICAL

The discovery of the intermediate stages and methods of entrance
into man of the human blood flukes is of very recent date. Guided by
the knowledge of the hfe eyeles of related forms, numerous workers
attempted without success to find intermediate hosts for these species.
After repeated efforts to find the larval stages of the Egyptian blood
fluke, Schistosoma haematobium, in Egyptian molluses, Looss finally
advanced the hypothesis that no intermediate host was needed in the
life eyele of this species and that man was infected by the miracidium
penetrating through the skin. According to this hypothesis, the inter-
mediate stages developed in the liver of man. Looss supported his
contention in a number of articles (1894, 1905, 1908, 1909), but with-
out adducing any positive experimental evidence. In fact, numerous
attempts to infect experimental animals directly with the miracidia
of the human schistosomes were entirely without success (Looss, 1905;

486 University of California Publications in Zoology [| Vou. 18

Tsuchiya, 1913; Conor, 1914). Looss explained these failures by
stating that since man was the only known host for this parasite
experiments on other animals were without significance. Looss’s
hypothesis of direct infection received the support of many parasit-
ologists and undoubtedly delayed the final discovery of the life cycle
of these forms.

The first successful experiments on the method of transmission of
the human schistosomes were carried on in 1909 by Japanese workers
with the Japanese species, Schistosoma japonicum. Katsurada and
Hashegawa (1910) showed that cats and dogs could be infected
through the skin with S. japonicum, by immersion in canal water in a
district where schistosomiasis was prevalent. Fujinami and Nakamura
(1909) sueceeded in infecting calves through the skin with this same
parasite. The first article by these authors was in Japanese, but their
results were included in a later publication by Fujinami (1914) in
German. In their first experiments the Japanese workers accepted
Looss’s hypothesis that the infective stage which penetrated the skin
of the host was the miracidium. Further studies, however, began to
throw doubt on this conclusion. Miyagawa (1912, 1913) studied the
infective stage just after penetration through the skin. In his de-
scription he noted the presence of suckers and other differences between
this stage and the miracidium. He therefore concluded that S. japon-
icum must have an intermediate host. Matsuura and Yamamoto (1912
and 1912a) studied infective stages of S. japonicum before they
entered the skin and Fujimami (1914, p. 22), with the aid of Naka-
mura and Narabayashi, studied newly penetrated schistosome larvae
in sections of new-born mice and rats. All of these workers noted
differences between the infective stage and the miracidium. Fujinami
(1914, p. 23) concluded from his studies that the miracidium did not
penetrate the skin in infection with S. japonicum. Tsuchiya (1913)
also came to the conclusion that the Japanese schistosome must require
an intermediate host for its development, since all attempts to produce
direct infection with the miracidium were without success. Katsurada
(1913, p. 371) in a summary of research on Japanese schistosomiasis,
abandoned Looss’s hypothesis of penetration by the miracidium, in
favor of a relatively simple metamorphosis of the miracidium prior
to skin infection. In this same paper published in December, 1913,
Katsurada (1913, p. 378) added a note to the effect that he had just
been informed that Miyairi of Kinshu had found the intermediate
stage of S. japonicum in a species of Lymnaea. Fujinami (1914,

1 This early identification was later corrected.

1919] Cort: The Cercaria of the Japanese Blood Fluke 487

p. 23) soon after this also published the statement that the intermediate
host had been discovered by Miyairi in a new species of Blanfordia.
These statements were the first hints to scientific workers outside of
Japan that this problem has been solved.

Credit for the discovery of the intermediate host ce the first
study of the larval stages of the Japanese blood fluke goes to two
Japanese workers, Miyairi and Suzuki (1913, 1914). Miyairi and
Suzuki solved the problem experimentally by infecting snails of the
species Blanfordia nosophora with the miracidia of S. japonicum.
They found that development of sporocysts containing cercariae fol-
lowed. The cercariae when fully developed escaped from the snails
and produced schistosomiasis by penetration through the skin of mice
exposed to the water containing infected snails. These authors also
deseribed and figured the structure of the stages found in the snails.
Two years later Leiper and Atkinson (1915) also produced experi-
mentally the development of the cereariae of S. japonicum in the
Katayama snail, Blanfordia nosophora (Robson). Adults of S. japon-
icum were experimentally developed in mice after skin penetration
of ecercariae so produced. Leiper and Atkinson (1915) briefly
described the sporocysts and cereariae and figured the snail inter-
mediate host and the larval stages. Appended to their account is the
description of the intermediate host by G. A. Robson as Katayama
nosophora nov. gen nov. spec. Fujinami (1914, p. 23) stated that this
snail is a new species of the genus Blanfordia. Miyagawa (1916,
p. 97) discussed fully the question of the systematic position and
name of the intermediate host of S. japonicum. He placed it in the
genus Blanfordia A. Adams, and accepting the priority of Robson’s
specific name designated it as Blanfordia nosophora (Robson). Since
the discovery of the intermediate host and cercaria of S. japonicum
additions to the knowledge of this stage have been made by a
number of Japanese workers. In 1916 Fujinami, Tsuchiya and
Miyagawa (1916) published in Japanese an extensive monograph
on Japanese schistosomiasis. In this monograph Fujinami con-
tributed the discussion on the history of the subject and the path-
ological anatomy, Tsuchiya the part on symptomology, and Miyagawa
the part on the etiology. ‘In his part of this monograph Miyagawa
(1916) gives the most extensive account of the intermediate host and
larval stages of S. japonicum to be found in the literature. He also
included a critical analysis of the Japanese work along this line
which proved to be very helpful. Parts of the papers of Fujinami

488 University of California Publications in Zoology [Vou. 18

(1916, part V) and of Miyagawa (1916) have been translated for me
by F. T. Konno, a Japanese student in the University of California.
It has been from this translation, from the reviews in the Tropical
Disease Bulletin, and from the reviews of Japanese medical literature
by Mills in the China Medical Journal, that material was obtained
for the discussion of Japanese papers which were not accessible. Other
Japanese writers who have contributed to the knowledge of the struc-
ture of the cerearia of S. japonicum are Ogata (1914) and Nara-
bayashi (1914, 1916). Notwithstanding the amount of work which has
been done on the intermediate stages of S. japonicum there is still
considerable confusion and difference of opinion in regard to the
structure of the cerearia.

The discovery of the intermediate hosts and larval stages of the
other two species of human blood flukes, 8S. haematobium and S. man-
som followed closely after that of S. japonicum. Leiper (1915, parts
I, II, I11) working in the same laboratory from which Looss tried so
long in vain to solve the life history of the Egyptian blood fluke
found the intermediate host of that species and studied its larval
stages. At first Leiper did not distinguish between the cereariae of
S. haematobium and S. mansoni. In later publications, however,
Leiper (1916, 1918) distinguished between the cercaria of S. haema-
tobium which develops in Bullinus contortus and Bullinus dybowski
and the cerearia of S. mansoni which develops in Planorbis boissyt.
Leiper did not attempt to make a critical structural analysis or com-
parison of the cercariae of these two species. Cawston (1915, 1916,
1917) reported the larval stages of S. haematobium in Physopsis
africana from South Africa. His descriptions and figures of this and
the other forked-tailed cercariae which he described are so entirely
inadequate that it seems to me that his entire work needs verification
by more competent observers. In the new world the intermediate host
of S. mansoni has been discovered in Venezuela by Iturbe and Gon-
zales (1917) in Planorbis guadelupensis Sowerby and by Lutz (1916
and 1917) in Planorbis olivaceus Spix. Lutz so far has published only
preliminary reports of his work, but promises the full account soon
in the Memorias do Instituto Oswaldo Cruz. A second paper by Iturbe
(1917) contained a fuller account of the anatomy of this cerearia. It
is very probable, as stated by Lutz (1916, p. 387), that Cercaria
blanchardi from Planorbis bahiensis was the cerearia of S. mansoni.
Da Silva’s description of this form is too brief to make certain deter-
mination possible, but agrees as far as it goes with the description of

1919] Cort: The Cercaria of the Japanese Blood Fluke 489

the cerearia of S. mansoni. Lutz (1916, p. 387) considers Planorbis
bahiensis to be a synonym of Planorbis olivaceus Spix. In a foot-
note to a review of Lutz’s second preliminary report (Trop. Dis. Bull.,
11, 79) Leiper makes the following statement: ‘‘Planorbis guade-
lupensis more recently implicated by Iturbe in Caracas is very similar
to, if not identical with, Planorbis olivaceus.’’? The solving of the
exact systematic relations of these hosts will have to await further
work. As can be gathered from this brief review of the literature
there still remains much work to be done on the larval stages of the
human schistosomes.

Studies on the human schistosomes are of peculiar importance to
California and the other Pacific coast states on account of immigration
from countries where schistosomiasis is prevalent. Records of the
United States Public Health Service and case records show that schis-
tosomiasis has been brought into this country. If suitable inter-
mediate hosts could be found this disease might become established,
especially since it can develop in cats, dogs, rats, cattle, and other
animals. In previous publications I have pointed out this danger and
have shown that trematodes of this type show considerable adaptability
in intermediate hosts (Cort, 19186, 1918c). Recently Reed (1918) has
also considered this subject. He discusses five cases of schistosomiasis
from California and mentions others which have come to his attention.
His conclusions in regard to the dangers to\ California from this
disease are similar to my own. One of the purposes of the present
paper is to aid investigations, which are being carried on to determine
whether the human schistosomes have found suitable intermediate
hosts in this country, by clearly defining the cerearia of S. japonicum.

MATERIAL

The material of the larval stages of S. japonicum on which the
studies included in this paper are based was obtained from living
specimens of the Katayama snail, Blanfordia nosophora (Robson),
which were sent to Professor C. A. Kofoid by Professor A. Fujinami
of Kyoto, Japan. To both of these gentlemen my sincerest thanks are
due for making possible this work. Blanfordia nosophora is an oper-
culate snail, and is very resistant to drying. The snails were shipped
across the Pacific Ocean in dust, and appeared, on arrival, to be
entirely dry and dead. They were placed in water in an aquarium
in the evening and the following morning were found to be actively

490 University of California Publications in Zoology [ Vou. 18

moving. A few of the original lot are still alive, having lived more
than a year in an aquarium. Since only a small percentage of these
snails were infected with cercaria of the Japanese blood fluke, the
material available for study was small. To make sure that the cereariae
found in the snails belonged to S. japonicum, two white rats were
infected through the skin. Post-mortem examination of these rats
made six weeks later revealed specimens of S. japonicum. On account
of the hmited amount of material no extensive infection experiments
or studies of the developmental stages between the cercariae and the
adult were attempted. In all, sporocysts and cereariae from five
infected snails were utilized in this study.

METHOD OF STUDY

The greater part of my observations of the cerearia of S. japon-
icum were made from living specimens. The method used in this
study of the living cerearia is the same that I have utilized in all
my recent studies on larval trematodes. It is discussed in detail in
previous publications (Cort, 1917, pp. 49-50 and 1918a, pp. 129-130).
The snails intended for study were carefully opened and the viscera
removed, so that the digestive gland was as little crushed as possible.
If the snail were infected with the cercariae the digestive gland would
have a yellowish diseased appearance, since it would be literally riddled
with the sporocysts. Snails were opened early in the morning and
the cereariae which would be present in an infected host in large
numbers could be kept alive a whole day in ordinary tap water.
Therefore each infected snail found, gave material for a whole day’s
intensive study of living cereariae. The cercariae, freed in a Syracuse
watch glass, were first studied with the lower powers of the microscope
to make an analysis of locomotion. Several cercariae were then trans-
ferred to a slide in a small drop of water and covered with a No. 1
cover glass. In order to slow down the movements sufficiently for
study it was necessary to remove slowly the water from the preparation
with a piece of blotting paper until the cover glass pressed on the
living cerearia. The cercaria could then be studied until the drying
and pressure of the cover glass caused it to go to pieces. I usually
found it convenient to make a half dozen or more of these prepara-
tions at a time. A single day’s study required the use of several
hundred preparations. The use of a compound binocular microscope
is indispensable for this type of work. The best results were obtained

1919] Cort: The Cercaria of the Japanese Blood Fluke 491

with an oil immersion lens and low oculars. This method of study
is tedious, hard on the eyes, and requires long practice to use effectively,
but gives extremely satisfactory results. Miyagawa (1916, p. 64)
noted the difficulty of observing the living cereariae on account of their
great activity. He advocates the method of intravitam staining as
employed by Narabayashi. I have, however, found no advantage in
intravitam staining in the study of a cerearia such as that of S.
japonicum in which the structures are clearly differentiated. To
check my observations on the living cercaria, serial sections were
made of a piece of a snail’s liver containing the sporocysts and
cereariae. These sections were cut five micra in thickness and stained
with Delafield’s haematoxylin with a counterstain of erythrosin. The
study of the sections served to corroborate the observations made from
the living animals and added certain important details.

CHARACTERS OF THE CERCARIAE OF THE HUMAN
SCHISTOSOMES

The cerearia of S. japonicum agrees with the cercariae of the two
other species of human schistosomes in a number of definite particulars.
Certain specific differences will be noted, but in the present state of
our knowledge it is difficult to discriminate clearly in morphological
characters between these three species of cercariae. This is undoubt-
edly due more to the limitations of our knowledge than to lack of
specific differences. The cercariae of the human schistosomes are very
small and develop in elongate motile sporocysts. They are fork-
tailed forms in which the divided lobes of the tail are less than half
the length of the main stem and definitely constricted from it. They
are without eyespots and pharynx and have a very rudimentary
digestive system. The whole surface of the body is covered with fine,
backward pointing spines. The ventral sucker is very small and in
the posterior third of the body length. The posterior half of the body
is filled with large unicellular glands, the ducts of which open at the
anterior tip after passing through a highly modified oral sucker con-
taining a central glandular reservoir. The reproductive organs of the
adult are represented by a small group of nuclei back of the ventral
sucker. The excretory system contains a very small number of flame
cells and a tubular bilateral type of bladder extending into the tail.
To sum up: the adult structures of the cercariae of the human
schistosomes are only slightly developed, and adaptive larval char-
acters for locomotion and penetration predominate.

492 University of California Publications in Zoology — [Vou. 18

STRUCTURE OF THE CERCARIA

Measurements of the cercaria of S. japonicum are very unsatis-
factory data for comparison, since the length of the living animal
varies greatly with extension and contraction. Preserved specimens
are much contracted and vary in length with the method of killing
and the contraction state when killed. Further, there is no evidence
that all cercariae of the same species will develop to the same size in
different sporocysts or different host individuals. Figure 1 is an enlarge-
ment from a camera lucida drawing of a slightly compressed cerearia
and gives an idea of the size and shape at an average state of extension.
The body of the cercaria has the power of extension to almost twice its
contracted length and the stem of the tail is capable of even greater
changes in length. The body of the cercaria and the stem of the tail
are cylindrical in cross-section. When the body is fully extended its
diameter may be reduced to that of the tail. Miyagawa (1916, p. 64)
gives the length of the body in well extended specimens as 0.09 to
0.21mm. Leiper (1915, p. 202) gives the body length of the specimens
of the cercaria of 8. japonicum measured by him as about 0.1 mm.
This measurement agrees with Miyagawa’s measurement on preserved
material. Leiper, however, does not state the condition of the speci-
mens which he measured.

The whole surface of the body and tail of the cercaria of S. japon-
icum is covered with backward pointing, cuticular spines. Beneath
the delicate cuticula are found two layers of muscles, an outer circular
and an inner longitudinal (figs. 1, 2). The individual strands of the
longitudinal layer have about twice the thickness of those of the
cireular layer. The body of the cercaria is so completely filled with
the various organs that the parenchymatous tissue is limited to a very
thin superficial layer (figs. 1, 2). Since the flame cells and tubules
of the excretory system develop in the parenchymatous tissue they are
also limited to this superficial region of the body.

The tail of the cercaria of 8. japonicum has well developed mus-
cular layers, especially in the stem region (fig. 1, st). The strength
of these muscles is shown clearly by the power of vibration, extension
and contraction which the tail possesses. The main stem of the tail
is round in cross-section, while the divided lobes which are definitely
constricted off from the stem are somewhat flattened. The parenchy-
matous tissue of the tail is dense, containing numerous nuclei obseur-

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Cort: The Cercaria of the Japanese Blood Fluke

493

Fig. 1. Cerearia of Schisto-
soma japonicum, ventral veiw;
as, anterior spines; b, excretory
bladder; bt, excretory bladder
of tail; cg, cephalic glands; em,
circular muscles; deg, ducts of
cephalic glands; ds, digestive
system; exp, excretory pore; f,
flame cell; hg, head gland; i,
island in excretory bladder; It,
lobe of tail; m, mouth; n, nerv-
ous system; st, stem of tail; s,
ventral sucker.

494 University of California Publications in Zoology [Vou. 18

ing the tubes of the excretory system, which can only be followed with
difficulty. In the main stem of the tail (fig. 1, st) there are two
lateral rows of large, fairly regular nuclei. The tail is an effective
muscular organ and is so attached that it is readily lost when the
cercaria starts to penetrate into its final host.

The ventral sucker (figs. 1, 2, s) is located at a point about three-
fourths of the distance from the anterior to the posterior end of the
body. It is circular in ventral view with a depth considerably greater
than its diameter (fig. 2). In the living animal the ventral sucker
can be protruded so that it has almost the appearance of a proboscis.
The sucker functions strongly in locomotion and is able to hold the
cercaria against considerable pressure.

I have already given in a previous publication (Cort, 1917, p. 52)
a preliminary description of the excretory system of the cercaria of
S. japonicum. The bladder (figs. 1, 2, b, bt) is composed of elongate
tubes and extends from the body into the tail. As in all fork-tailed
cercariae I have ever observed, there are two excretory pores (fig. 1,
exp), one on each of the divided lobes of the tail. The sides of
the V-shaped, bladder tubes of the body unite at the posterior end and
pass into the main stem of the tail as a single tube, which divides to
send branches to the pores at the tips of the bifurcations of the tail.
At the pores the tubes are slightly enlarged (fig. 1, erp). There is a
characteristic anastomosis in the tube of the bladder just where it
enters the tail, forming a little island (fig. 1, 7). The bladder in the
body (figs. 1, 2, b) which after the loss of the tail becomes the bladder
of the adult, is V-shaped. The sides of the V extend from their point
of union at the posterior end of the body along the ventral surface
to a region in front and to each side of the ventral sucker. They then
turn dorsad and pass along the sides of the cerearia still in the super-
ficial layer of parenchymatous tissue to the points on each side where
they receive the anterior and posterior collecting tubes (fig. 2, act,
pct). Two ciliated areas (fig. 2, ca) are present on each side near the
ends of the sides of the bladder. The collecting tubes (figs. 2, 3, act,
pet) are short and each receives the capillaries from two flame cells,
making four flame cells on each side, three in the body and one in the
anterior part of the stem of the tail (figs. 2, 3, f). The positions of
the flame cells are clearly indicated in figure 2. . The complete
excretory system of the cerearia of S. japonicum is shown diagram-
matically from the ventral side in figure 3. The cerearia of S. japon-
icum has the smallest number of flame cells that I have ever observed

1919 ] Cort: The Cercaria of the Japanese Blood Fluke 495

in a fully developed cercaria or seen recorded in the literature. The
whole system in the body is limited to the superficial layer of paren-
chymatous tissue, and almost all of the anterior half of the body of
the cercaria is without flame cells. However, the total mass of the
body of the cerearia is so small that no part is far from a flame cell.
I will not discuss here the general homologies of the excretory system of
the forked-tailed cercariae, since this subject was taken up in previous
publications (Cort, 1917, 1918). Previous knowledge of the excretory
system of the cercaria of the human schistosomes is very slight.
Miyagawa (1916, p. 67, pl. 4, fig. 30) saw only the main tubules of
the excretory system in the body and missed its connections in the tail.
Miyairi and Suzuki (1914) stated that the excretory system of the
cercaria of S. japonicum has five pairs of flame cells. Ogata (1914)
found two paired, laterally symmetrical flame cells with vessels. Iturbe
(1917, p. 433, fig. 1) located five pairs of flame cells in the cerearia of
S. mansoni, including one pair in the tail, but neither describes nor
figures the rest. of the system. From my knowledge of the homologies
of the excretory systems of the fork-tailed cerearia in general I would
expect to find this system in the cereariae of S. mansoni and SV.
haematobium corresponding closely to the conditions just described
for the cerearia of S. japonicum.

The central nervous system of the cerearia of S. japonicum (figs.
1, 2, n) is a bilobed mass back of the oral sucker and dorsad to the
ducts of the cephalic glands. No attempt was made to trace the nerve
trunks leading from this mass.

It was not possible to distinguish morphologically between male
and female cereariae, and the only trace of the complicated reproduc-
tive systems of the adult is a small mass of nuclei on the ventral side
back of the acetabulum (fig. 1, r). The extreme immaturity of this
type of cercaria is emphasized when we consider how completely the
structure of the adult schistosomes is dominated by secondary sexual
characters and the complex reproductive systems.

The digestive system of the cerearia of S. japonicum is in a very
rudimentary condition (figs. 1, 2, m, ds). The mouth is situated on
the ventral surface a little distance back of the anterior tip. A very
narrow buccal cavity passes through the oral sucker. The esophagus
extends from the posterior limit of this cavity to about the midline
of the body dorsad to the cephalic glands, where it widens into a
heart-shaped structure which represents the beginnings of the bifur-
cations of the intestinal caeca. The remarkable thing about this

496 University of California Publications in Zoology [Vou.18

digestive system is that the mouth is located on the ventral surface
quite a little distance back of the anterior tip and not at the anterior
tip, as believed by other workers on this species. Ssinitzin (1909)
noted this same relation in the digestive system of Cercaria ocellata
La Valette, which is a schistosome cercaria of the group with eyespots.
His description and figures of the digestive system in this form
(Ssinitzin, 1909, p. 317, pl. 10, figs. 22, 23) agree almost exactly with
the description just given for the cerearia of S. japonicum. Miyagawa
(1916, pl. 4, fig. 30) notes the same rudimentary condition of the
esophagus and intestinal caeca in his studies on the cerearia of S.
japonicum. He, however, considers that the mouth is at the anterior
tip, although he does not adequately describe or figure its relations
to the digestive tract in the oral sucker. Leiper (1915, fig. 2) figures
the intestinal caeca as very wide tubes extending to each side of the
ventral sucker. The esophagus he shows to be very short. In fact, his
description and drawing of this structure are very different from
Miyagawa’s and my own. I believe that Leiper must have confused the
lobes of the nervous system with the digestive caeca, since he does not
show these structures. In view of Ssinitzin’s finding in Cercaria
ocellata and my own in the cerearia of S. japonicum, I would expect
to find such a rudimentary digestive tract as that described above in
all fully developed schistosome cereariae.

ORAL SUCKER AND CEPHALIC GLANDS

The oral sucker (figs. 1, 2) of the cerearia of S. japonicum is so
remarkably modified by adaptive larval characters that it has little
resemblance to the oral sucker of the adult into which it develops. It
has a length of more than one-third the length of the body, and has
distinctly separated anterior and posterior regions. In its anterior
region it is in direct contact with the cuticula. The layers of circular
and longitudinal muscle fibers of the body wall, which are strengthened
in this region, form its outer limits. The posterior region of the oral
sucker does not come into contact with the body wall, but is separated
from it by a considerable layer of parenchymatous tissue, and tapers
posteriorly in the shape of a blunted cone. This posterior region is
surrounded by a thick layer of circular muscles (figs. 1, 2, em), the
fibers of which appear in the drawings in optical section. Within
the circular muscle layer is a thinner layer of longitudinal muscles.
The line of separation between the anterior and posterior regions of

497

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The Cercaria of the Japanese Blood Fluke

Cort

1919]

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ee . a ZA <!

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i

E-LD B
a Z A

side view; letters as before; also
pet, posterior collecting tube.

Cerearia of Schistosoma japonicum,

act, anterior collecting tube; ca, ciliated areas;

Fig. 2.

I

498 University of California Publications in Zoology (Vou. 18

the oral sucker is very clearly defined in a living cerearia or toto
mount. Under certain conditions this line appears as a constriction
which separates the so called ‘‘head’’ of the cerecaria from the body
proper.

The center of the oral sucker contains a large reservoir-like gland
(fig. 1, 2, hg) which opens almost exactly in the middle of the anterior
tip. This is called the ‘‘head-gland’’ by Miyagawa (1916, p. 67). As
noted by Miyagawa it is more coarsely granular than the cephalic
glands which fill the posterior half of the body. I will include a trans-
lation of the discussion in Miyagawa’s paper (1916, p. 67) in regard
to this gland:

Head-gland = Kopfdruse (of Narabayashi).
This gland oceupies about half of the head at the dorsal part of the center.
It contains coarse granular material and is stretched or compressed with the
movements of the cerearia. It opens at the anterior end of the oral sucker.
This sac-like gland has been confused by many investigators with the buceal
cavity. In larvae examined after entering the skin it was found to be pressed
to one side and later disappeared.

Since the head-gland degenerates soon after the cercaria has pene-
trated through the skin of its final host, Miyagawa considered that it
is an adaptive larval structure which has some function connected
with penetration. Its position would also seem to support this view.
A layer of large nuclei surround the gland and are evidently a part
of it. The contrast between the head-gland and the cephalic glands
(figs. 1, 2, eg) is shown very clearly by reactions of their glandular
substances to stains. The head-gland in the sections studied took the
red stain (erythrosin), while the cephalic glands were stained a lght
blue with haematoxylin.

The remainder of the oral sucker is filled with parenchymatous
tissue and the anterior portions of the ducts of the cephalic glands
(figs. 1, 2, deg). The consistency of the oral sucker is such that its
shape can be greatly distorted by contraction of its muscles. The
ducts from the cephalic glands (figs. 1, 2, deg) pass into the oral sucker
on each side near its ventral surface. They pass directly through the
muscular boundary of the sucker and run forward along each side to
open at the anterior tip of the cercaria. Near the openings of these
ducts at the anterior tip are located on each side four or five, forward
pointing spines (figs. 1, 2, as). The relations of the different parts
included in the oral sucker are shown clearly in figures 1 and 2. The
oral sucker is not radially symmetrical as is usually the case, but has _

1919] Cort: The Cercaria of the Japanese Blood Fluke 499

a dorsoventral differentiation depending on the position of the ducts
of the cephalic glands, the mouth and buccal cavity. This dorso-
ventral differentiation is also clearly indicated by the shape of its
posterior region. That this unusual differentiation of the oral sucker
is probably common to all true schistosome cercariae is suggested by
the description of a similar differentiation of the oral sucker of

Fig. 8. Diagrammatic representation of the excretory system of the cercaria
of Schistosoma japonicum, ventral view; letters as before.

500 University of California Publications in Zoology [| Vou. 18

Cercaria ocellata La Valette as described by Ssinitzin (1909, p. 316,
pl. 10, figs. 22, 23, 26). This author shows clearly the layer of circular
muscles of the posterior region of the oral sucker, the positions of
the ducts of the cephalic glands passing through the sucker and the
position of the mouth on its ventral surface. Most of the descriptions
of schistosome cereariae do not show the details of this organ. In
my figures (Cort, 1915, p. 50, pl. 7, figs. 59-62) of the oral sucker
of Cercaria douthitti the passage of the ducts of the cephalic glands
through the oral sucker is clearly brought out, although the other
parts are not entirely clear. In recent studies of an undescribed
species of schistosome cerearia with eyespots I found the structures of
the oral sucker to be much the same as in the cerearia of S. japonicum,
including the thick circular muscular layer of the posterior region,
the head-gland, and the spines at the openings of the ducts of the
cephahe glands.

The cephahe glands (figs. 1, 2, eg) are unicellular with large nuclei
filling almost all of the posterior half of the body. I counted five of
these glands on a side. The ducts from the cephalic glands pass
forward in two groups ventrad to the central nervous system and
digestive tract and enter the oral sucker as described above. These
glands are loose in texture, the bulk of each gland apparently consist-
ing of secretory products and are pushed into all sorts of shapes by
changes in the shape of the body of the cerearia. It is not easy to
distinguish clearly the outlines of the cephalic glands and to determine
their exact number. Leiper (1915, p. 202) stated that there are five
or more of these glands on each side. I have, however, never noted
any variation in their number in different cercariae. Miyairi and
Suzuki (1914), Ogata (1914), and Miyagawa (1916, p. 66, pl. 4, fig.
30) noted only three pairs of these glands in their descriptions of the
cercaria of S. japonicum. Miyagawa’s figure (1916, fig. 30) shows the
cephalic glands as six small bodies between the digestive caeca and
the acetabulum, filling only a small part of the posterior body region.
My observations lead me to beleve that Miyagawa’s drawing is
incorrect in this particular.

The total bulk of these glands and their ducts, which is more than
half the total bulk of the body of the cerearia, indicates that they
perform an important function. The cephalic glands of the fork-
tailed cercariae appear to be homologous to the stylet glands of the
xiphidio-cercariae which open at the base of the stylet or piercing
organ, and to which the function of dissolving tissue in connection

1919] Cort: The Cercaria of the Japanese Blood Fluke 501

with the penetration of the cercaria into its host has been ascribed by
certain authors. A full account of the functioning of the stylet glands
in penetration was given almost twenty-five years ago by Looss (1894,
pp. 127, 238). Faust (1918, p. 34), following La Rue’s analysis (1917,
p. 5) of similar glands in an agamodistome, calls the cephalic glands
of the fork-tailed cercariae mucin glands. Miyagawa (1916, p. 366),
following Miyairi and Suzuki (1914), called the cephalic glands of
the cerearia of S. japomcum ‘‘poison glands.’’ I prefer the term
cephalic gland, since the ducts of these glands open at the anterior
tip of the cerearia. My studies lead me to believe that these cephalic
glands function in penetration, probably by dissolving tissue. Instead
of a single stylet as in the xiphidio-cereariae, the schistosome cereariae
have a number of spines around the openings of the cephalic glands
which perform the same function as the stylet in penetration. Besides
producing a cytolytic secretion which dissolves the tissues of the host
and thus aids the cercaria in penetration, it seems probable that the
secretions of these glands neutralize the toxic secretions that the host
produces in its attempt to combat the entrance of the cercariae.
Mivagawa (1916, p. 66) stated that these glands must have something
to do with penetration since, according to his observations, they dis-
appear soon after the cercaria has entered the body of the host.
Leiper (1915, part IIT, p. 260) also suggested that these glands in the
eercaria of S. haematobium function in penetration. The head-gland
which also disappears after the cercaria has entered the body of its
host, seems also to function in penetration. The productions of
eosonophil cells by the host in connection with the penetration of
the schistosome cerearia, suggests that the host is actively combating
the entrance of the parasite by the production of toxins. This may
be taken as evidence of the battle which is waged between the host
and the entering parasite. It seems to me very probable that the
head-gland and the cephalic glands are the batteries of the cercaria
in this fight, which in the offensive of the human schistosome cercariae
give such striking success to the invaders. Certain of the movements
of the anterior end of the cerearia of S. japonicum observed in con-
nection with the activities of the living animal support the theory that
the cephalic glands function in penetration. This evidence will be
brought out in connection with the discussion of the activity of the
living cerearia.

502 Unwersity of California Publications in Zoology [Vou 18 -

ACTIVITY OF THE CERCARIA

The cercaria of S. japonicum when freed from its sporocysts in a
watch glass swims freely for a short time and then settles down to the
surface where it moves by a looping movement. It has a strong positive
thigmotropism, so that whenever any part of its body touches a sur-
face the cercaria immediately adheres to it and starts moving on it.
In fact, this cercaria is apparently better adapted for locomotion on
a substratum than for free swimming. In swimming the movement
of the cerearia of S. japonicum consists of a vibration of both the
body and the tail which carries the animal either forward or backward
in an irregular course through the water. The movement is more often
backward than forward. During the vibration the body is slightly
contracted, but the stem of the tail is considerably elongated. The
posterior end of the body and the point of bifurcation of the tail are
relatively constant points, while the anterior end of the body and
the middle of the stem of the tail vibrate backward and forward so
rapidly that they disappear from view.

The method of locomotion on a substratum is also very character-
istic. It is a modification of the ordinary looping movement common
to so many distome cercariae (see Cort, 1915). The cerearia is able
to take hold both with the ventral sucker and the anterior tip. Its
method of taking hold with the anterior tip is very characteristic.
In trematodes, both cereariae and adults, in which the oral sucker is
fully developed, the suction which allows this sucker to take hold is
produced. by the action of the muscles of the sucker in connection
with the mouth and buceal cavity. In the cerearia of 8. japonicum
the sucking action of the anterior end is developed in an entirely
different way and has no connection with the mouth or buceal cavity.
As long as a cercaria is alive the anterior tip keeps rolling in and out
by the interaction of the strong circular and longitudinal muscles of
the anterior region of the oral sucker, and the circular muscles of
the posterior region. The exact mechanism of this rhythmic action
is not clear but the sequence of movements is about as follows: The
strong contraction of the circular muscles of the posterior region of
the oral sucker presses this organ forward and causes the anterior end
to be thrust out with the openings of the cephalic glands and the
spines surrounding them at the anterior extremity. This is followed
by a rolling-in of the tip for a considerable distance. This rolling-in

1919] Cort: The Cercaria of the Japanese Blood Fluke 503

pushes the ends of the ducts of the cephale glands with their spines
well back into the middle of the sucker and produces a cavity at the
anterior tip lined with the surface spines. It is this rolling-in action
of the anterior tip which makes suction possible.

The locomotion on a substratum of the cerearia of S. japonicum con-
sists of an alternate taking-hold and loosening of the ventral sucker
and the anterior tip. In initiating locomotion on a substratum the
cerearia takes hold with its ventral sucker and stretches out its body
to about one and one-half times the normal length. The extended
body may sway backward and forward and reach around as if it
were exploring. At greatest extension the body, which at this time
has a width no greater than the width of the tail, bends over and the
anterior tip takes hold, then the ventral sucker is loosened and is pulled
forward to take hold just back of the anterior tip; this causes the body
to arch up. After the ventral sucker takes hold the anterior tip is
loosened and the preacetabular region is again extended and takes hold.
Each time the body is bent up for the ventral sucker to take a new
hold the tail is vibrated. Quick repetitions of this movement produce
a fairly rapid locomotion. The bending-up of the body and the taking
hold by the ventral sucker are accomplished so quickly that the cerearia
gives the impression of moving across the surface by a series of Jumps.
Even if the anterior tip does not get a hold, as is often the case in
movement on a smooth surface, the cercaria will make progress, since
the ventral sucker, aided by the vibration of the tail, will gain a hold
in advance of its previous hold. At the initiation of the movement
when the anterior end is at its greatest extension the openings of the
ducts of the cephalic glands with their spines are just at the anterior
tip, but when the worm bends over to take hold the anterior tip is
rolled in, so that the openings of these ducts point toward the center
of the oral sucker and the surface which catches hold is covered with
spines.

Certain of the activities of the cercaria of S. japonicum show direct
correlation with penetration into the human host. The tendency of
the cerecaria to adhere and move on the surface of any object with
which it comes in contact would tend to bring it into relation to this
host. In several instances cercariae were watched when attached by
their ventral suckers to pieces of snail tissues. When in this position
the preacetabular region reaches out in all directions in an éxploring
movement. This movement, combined with the rhythmical pushing
out and rolling in of the anterior tip made the cereariae look as if

504 University of California Publications in Zoology | Vou. 18

they were exploring with the anterior end to find a point where they
could push in. That the pushing out of the anterior tip exerts con-
siderable force was shown by the observation that when the cerearia
was in contact with loose pieces of débris it would push them away
by this movement. I also saw cercariae forcing their way through the
loose tissue of the snail or disintegrating sporocysts. The extension
of the body combined with the pushing out of the anterior tip forced
the tip of the worm into the tissue. The backward pointing, cuticular
spines of the body held what was gained and the new extensions of
the body produced further progress. Several times in connection with
the progress of cereariae through tissue, bubbles of secretions from the
cephalic glands were seen to be forced out when the anterior tip was
extended to its utmost. The above observations and a consideration
of the relations of the adaptive larval characters of the cercaria of
S. japonicum gives us an idea of how it penetrates the human host. The
cercariae freed from the snail in the rice fields would be stirred into
activity by the passage of the host. Coming in contact with the sur-
face of the skin the cerearia would catch hold with the ventral sucker
and by the extension of its body and the butting with the spines. of the
tip would produce a slight opening. Aided by the eytolytie secretions
of its glands, the backward pointing spines and its movement, the
cerecaria would rapidly take advantage of the opening to penetrate
through the skin of the host. In fact, the cerearia of S. japonicum
is primarily a machine for skin penetration and its structure is com-
pletely dominated by those adaptive larval characters which make
possible its penetration into the human host.

1919] Cort: The Cercaria of the Japanese Blood Fluke 505

LITERATURE CITED

CawstTon, F. G.
1915. Schistosomiasis in Natal. Jour. Trop. Med. Hyg., 18, 257-258, 4 figs.
1916. The cereariae of Natal. Ibid., 19, 201-202, 8 figs.
1917. The cereariae of Natal. Jour. Parasit., 3, 131-135.
Conor, A.
1914. Hssais de transmission de la bilharziose. Bull. Soe. path. exot., 7,
202-206.
Cort, W. W.
1915. Some North American larval trematodes. Illinois Biol. Monographs,
1, no. 1, pp. 1—71, pls. 1-8.
1917. Homologies of the excretory system of the forked-tailed cerecariae.
A preliminary report. Jour. Parasit., 4, 49-57, 2 figs. in text.
1918. The excretory system of Agamodistomum marcianae (lia Rue), the
agamodistome stage of a forked-tailed cerearia. Jour. Parasit.,
4, 130-134, 3 figs. in text.
1918a. Methods for studying living trematodes. Trans. Amer. Micr. Soce.,
37, 129-130.
1918b. Dangers to California from oriental and tropical parasitic diseases.
Calif. St. Bd. Health, Spec. Bull. 29; also Mon. Bull. 14, 6-15.
1918¢c. Adaptability of schistosome larvae to new intermediate hosts. Jour.
Parasit., 4, 171-173.
Da SiLva, M. P.
1912. Cercaire bresilienne (Cercaria blanchardi) a queue bifurquée. Arch.
Parasit., 15, 398-400, 3 figs. in text.
Faust, E. C.
1918. Life history studies on Montana trematodes. Illinois Biol. Mono-
graphs, 4, no. 1, pp. 1-102, pls. 1-9.
FugINAMI, A.
1914. Ueber die Bekimpfung der japonischen Schistosomumkrankheit,
nebst einer kurzen Schilderung der Pathologie dieser Krankheit.
Estratto dalle ‘‘ Ricerche di Biologia dedicate al Prof. Allesandro
Lustig nel 25° anno del suo insegnamento universitario,’’ 1914,
pp. 138-42, 3 pls.
FuJINAMI, A., AND NAKAMURA, H.
1909. New researches on the Japanese schistosomiasis. (Japanese.) Kyoto
Igaku Zassi, 10. (Quoted from Fujinami.)
FuJINAMI, A., TSucHIYA, J., AND MiyaGAwa, Y.
1916. Concerning Japanese schistosomiasis. (Japanese.) New Jour. Japan.
Mediates: 50) 1 2Gie pls. 1-9:
Part I. History, by A. Fujinami, pp. 2-20.
Part II. Etiology, by Y. Miyagawa, pp. 21-100, pls. 1-5.
Part III. Pathological anatomy, by A. Fujinami, pp. 101-182,
pls. 6-9.
Part IV. Symptomology, by I. Tsuchiya, pp. 183-254.
Part V. Literature, by A. Fujinami, pp. 255-267.

506 University of California Publications in Zoology — [Vou. 18

ITURBE, J.
1917. The anatomy of the cercaria of S. mansoni. New Orleans Med. Surg.

Jour., 70, 433, 1 fig. in text.
ITURBE, J., AND GONZALEZ, E.

1917. The intermediate host of Schistosomum mansoni in Venezuela, pp. 1-8,
pls. 1-2. (Reprinted in special edition by the National Academy
of Medicine.)

KATSURADA, F.
1913. Schistosomiasis japonica. Centralbl. f. Bakt. Parasit. u. Infek., 1
Abt. Orig., 72, 363-379, 2 pls., 2 figs. in text.
KATSUARDA, F., AND HASHEGAWA, T.

1910. Bemerkungen sur Lebensgeschichte des Schistosomum japonicum Kat-

surada. Ibid., Orig., 53, 519-522, 1 fig. in text.
La Rug, G. R.

1917. Two larval trematodes from Thamnophis marciana and Thamnophis
eques. Occasional Papers, Mus. Zool., Univ. Mich., no. 35, pp. 1-12,
1 pl.

LEIPErR, R. T.

1915. Report of the results of the Bilharzia Mission in Egypt, 1915. I,
Transmission; II, Prevention and eradication; III, Development.
Jour. Roy. Army Med. Corps, 25, 1-55, 147-192, 253-267.

1916. On the relation between the terminal-spined and lateral-spined eggs
of Bilharzia. Brit. Med. Jour., p. 411, March 18.

1918. Report on the results of the Bilharzia Mission in Egypt, 1915. V,
Adults and ova. Jour. Roy. Army Med. Corps, 30, 235-260.

LEIPER, R. T., AND ATKINSON, E. L.
1915. Observations on the spread of Asiatic schistosomiasis; including
*‘Note on Katayama nosophora,’’ by G. C. Robson. Brit. Med. Jour.,
pp. 201-203, 1 pl., January 30.
Looss, A.
1894. Bemerkungen zur Lebensgeschichte der Bilharzia haematobia im An-
schlusse an G. Sandison Broek’s Arbeit iiber denselben Gegenstand.
Centralbl. f. Bakt. Parasit. u. Infek., 16, 286-292, 340-346.
1894a. Die Distomen unserer Fische und Froésche. Bibl. zool., 16, 1-226, pls.
1-9.
1905. Histoire naturelle de la Bilharzia. I°™ Congrés égyptien de medicine,
C.-R. II, Chirurgie, pp. 83-18. (Quoted from Leiper.)
1908. What is Schistosomuwm mansoni? Ann. Trop. Med. Paras., 2, 153-191.
1909. Bilharziosis of women and girls in Egypt in the light of the ‘‘skin
infection theory.’’ Brit. Med. Jour., pp. 773-777, March 27.

1916. Abservacées sobre a evolucao do Schistosomum mansoni; Nota previa.
Brazil Medico., 30, 385-387. (Abstracted in Trop. Dis. Bull. 9, file)

1917. Abservacdes sobre a evolucio do Schistosomum mansoni; Secunda nota
previa. Brazil Medico, 31, 81-82, 89-90. (Abstracted in Trop. Dis.
Bull. 11, 78-79).

MatsuuRA, U., AND YAMAMOTO, J.

1912. The morphology of the Japanese schistosome at the time of entering
the skin. (Japanese.) Chugwai-Iji-Shinpo, no. 752. (Cited from
Fujinami.)

1919] Cort: The Cercaria of the Japanese Blood Fluke 507

1912a. The morphology of the Japanese schistosome in the poisonous ditch
water before entering the animal body. (Japanese.) Chugwai-Iji-
Shinpo, no. 755. (Cited from Fujinami.)

Mriyairi, K., AND SuzuKI, M.
1913. On the development of Schistosoma japonicum. (Japanese.) Tokyo-
TjiShinstu, no. 1836. (Reviewed in Trop. Dis. Bull. 8, 289-290.)
1914. Der Zwischenwirt des Schistosomum japonicum Katsurada. Mitt. a. d.
med. Fak. d. k. Univ. Kyushu Fukuoka, 1, 187-197, 2 pls. (Re-
viewed in Trop. Dis. Bull. 8, 506-508.)

Miyacawa, Y.

1912. Ueber den Wanderungsweg des Schistosomum japonicum von der Haut
bis zum Pfortadersystem und itiber die Korperkonstitution der
jiingsten Wiirmer zur Zeit der Hautinvasion. Centralbl. f. Bakt.
Parasit. u. Infek., 1 Abt. Orig., 66, 406-416.

1913. Ueber den Wanderungsweg des Schistosomum japonicum durch Ver-
mittlung des Lymphgefiasssystems des Wirtes. Jbid., Orig., 68,
204-206. %

1916. Concerning Japanese schistosomiasis. II, Aetology. (Japanese. )
New Jour. Japan. Med. Res., 6, no. 1, pp. 21-100, pls. 5. (See
Fujinami, Tsuchiya, and Miyagawa, 1916.)

NARABAYASHI, F.

1914. Morphology and infecting tract of young adults of Japanese schisto-
somiasis at the time of entering the skin of the host. (Japanese.)
Jour. Japan. Path. Soe. ( Quoted from Fujinami.)

1916. Contribution to the life history of Schistosomum japonicum. Kyoto
Tgaku Zassi., 22, no. 3, pp. 1-63, July 20. (Reviewed in China Med.
Jour, ol, no. 1, pp, 80-81).

Ogata, S.

1914. Ueber den anatomischen Kérperbau der Cerecarien des Schistosomum
japonicum und die Uebertragungsweise derselben auf Tiere. Ver-
handl. d. japan. path. Ges., Tokyo, 1914, 48. (Reviewed in Trop.
Dis. Bull. 9, 269.)

REED, A. C.
Schistosomiasis in California. Calif. St. Med. Jour. 16, 293-296.

SsIniTzi1n, D. T.
1909. Studien iiber die Phylogenie der Trematoden. IT, Bucephalus v. Baer
* und Cercaria ocellata La Valette. Zeitschr. f. wiss. Zool., 94, 299-
325, pls. 8-9.
TsucuHiya, I.
1913. Clinical, pathological, anatomical, pathogenic, prophylactic and thera-
peutic study of Schistosomiasis japonica. (Japanese.) Sei-i-Kwai
Med. Jour., 32, 107-109. (Abstracted in Trop. Dis. Bull. 2, 406—
407.)

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UNIVERSITY OF CALIFORNIA PUBLICATIONS
IN

ZOOLOGY
Vol. 18, No. 18, pp 509-519, 7 figures in text January 4, 1919

NOTES ON THE EGGS AND MIRACIDIA OF
THE HUMAN SCHISTOSOMES

BY
WILLIAM W. CORT

INTRODUCTION

During the spring of 1917 through the kindness of Dr. J. P.
Hickey of the United States Public Health Service, I obtained fecal
samples from three cases of schistosomasis. One of these samples
contained eggs of Schistosoma mansoni and the other two contained
eges of S. japonicum. This material was used primarily for experi-
mental work, but gave an excellent opportunity for careful study of
the eggs and miracidia in the living condition. An examination of the
literature shows that, although the structure of the miracidium of
S. haematobium had been carefully worked out twenty-five years ago
(Looss, 1893, 1894), the descriptions and figures of this stage in SV.
manson and S. japonicum are still inadequate.

THE EGG AND MIRACIDIUM OF SCHISTOSOMA MANSONI

Figure 1 is a microphotograph of an egg of Schistosoma manson
showing its general shape and the position of the spine, and figures 2,
3, and 4 are drawings of the miracidium of this species, showing the
details of structure as they appear in optical section of the living
animal. It is interesting to note that in the egg the position of the
miracidium may be either with the anterior papilla toward the spine
(fig. 3) or away from the spine (fig. 4). Conor (1910, p. 533) noted
this same difference of position of the miracidium of S. haematobium
within the egg. In forty counts of this species he finds the anterior
papilla toward the spine and in one hundred and seventy, away from

510 Unversity of California Publications in Zoology [Vou.18

it. The shell of the egg of S. mansoni is very tough and resistant.
Attempts were made to break open the eggs and free the miracidia by
pressure on the cover glass. Often the egg would be pressed to twice
its normal diameter before the shell would break. Even then, in a
number of instances, the miracidium escaped undamaged. The inside
of the shell is lined with a thin vitelline membrane (fig. 4, vm). In
several instances when the shell was broken by pressure, the vitelline
membrane came away intact, surrounding the miracidium like a veil,
and it required considerable activity of the miracidium to free itself
from the membrane. Looss (1893, pp. 521, 522) described the vitelline
membrane in the egg of S. haematobium as a colorless, finely granular

Fig. 1. Microphotograph of the egg of Schistosoma mansoni. Photograph
taken by Dr. J. P. Hickey.

membrane with projecting nuclei here and there. The space between
the vitelline membrane and the embryo contains granules and oil
globules. These oil globules are secreted by the anterior ducts (fig. 2,
ad). Holeomb (1907, pp, 66, 67) speaks of these oil elobules as
opalescent bodies and considers them to be food for the embryo. The
anterior ducts and their secretion will be discussed more fully in con-
nection with the description of the miracidium of S. japonicum.
When freed from the egg the miracidium swims actively, rotating
on its long axis. The shape assumed in swimming is similar to that
of the miracidium of S. japonicum (fig. 5). The miracidium is very
mobile and changes its shape greatly when pushing through the
débris on a slide. I have seen no such extreme elongation as Holeomb
(1907, fig. 4) figured, and believe it very improbable that the mira-
cidium of S. mansoni could possibly assume such a shape while swim-
ming. The anterior papilla, which is the only part of the surface of

1919] Cort: Eggs and Miracidia of Human Schistosomes oilee

the body without cilia, is constantly pushed forward and withdrawn
when the miracidium is moving in débris. The firm nature of this
papilla was shown by the way it could push aside the particles with
which it came in contact.

The cephalic glands (figs. 2, 3, 4, cg) of the miracidium of Schisto-
soma mansoni are somewhat larger in proportion to the length of the

O.03 7-717.

Fig. 2. Miracidium of 8S. mansoni, from glandular surface; ad, anterior
ducts; ap, anterior papilla; eg, cephalic gland; exp, excretory pore; f, flame
cell; ge, germ cell; n, central nervous mass; rd, rudimentary digestive sac.

*

body than in the miracidium of the other two species of human
schistosomes. The position of their ducts and their similarity to the
cephalic glands of the schistosome cereariae suggest that their secretions
may aid in the penetration of the miracidium into the intermediate
host, either by dissolving the tissue or by neutralizing the secretions
of this host. The cephalic glands are unicellular, with large nuclei.

512 University of California Publications in Zoology [| Vou. 18

The central nervous system is an oval, slightly irregular mass lying
about the center of the body (figs. 2, 3, 4, n). My observations on
the hving animal did not reveal the nerve fibers going out from this
central mass as shown by Looss (1896, p. 165, pl. 11, fig. 113). Hol-
comb (1907, p. 68) entirely misses the significance of this structure,

Fig. 3. Miracidium of S. mansoni within the egg, from neural surface;
letters as in figure. 2.

and calls it a viscus or stomach connected with the anterior end by an
esophagus. He was also confused in regard to the structures of the
posterior part of the body. His errors are surprising, since an
acquaintance with the general structure of the miracidium stage of
the trematodes or with the description or figures of the miracidium
of Schistosoma haematobium would have made them impossible. It is
unfortunate that his figures have found their way into some of the

1919 | Cort: Eggs and Miracidia of Human Schistosomes ls

standard textbooks, since they give an entirely erroneous picture of
the structure of the miracidium of S. mansoni.

I was unable to trace completely the connections of the tubules of
the excretory system in this miracidium. The excretory pores (fig. 2,
exp) are located on each side of the body near the posterior end.

O.O5 mr

Fig. 4. Miracidium of S. mansoni within the egg, lateral view; letters as
in figure 2; also vm, vitelline membrane.

Four large flame cells (fig. 4, f) are present, draining the anterior and
posterior regions on each side. The individual flame cell is very
large in proportion to the size of the miracidium, having a length
of about one-third the width of its body. The flame cells in the
miracidium of Schistosoma mansoni differ in position from those of
the miracidia of S. haematobium and S. japonicum, since they lie
almost perpendicular to the long axis (ef. figs. 4, f; 6, f). For this

514 University of Califorma Publications in Zoology [ Vo. 18

reason they appear, except in side view in optical section of the living
miracidium, merely as ciliated holes (figs. 2, 3, f). This appearance
confused Holeomb (1907, p. 68) who misinterpreted them entirely.
Only the beginnings of the capillaries were made out. I could dis-
tinguish coiled tubules on each side, but could not trace their con-
nections. In view of the position of the excretory pores and flame
cells it is very probable that the excretory system in this miracidium
is similar to that of the miracidium of S. japonicum (fig. 6, 7).

Functionally the schistosome miracidium appears to have no dorso-
ventral or lateral differentiation, since it is round in cross-section and
revolves on its long axis in locomotion. Structurally, however, this
differentiation is very striking. The arrangement of the excretory
system and cephalic glands gives a very clear bilateral symmetry. The
cephalic glands le nearer one surface of the body, and the central
nervous body and rudimentary digestive sac lie nearer the other.
Since the use of the terms dorsal and ventral are meaningless for such
a type as this miracidium, I propose that these surfaces be designated
respectively the glandular and neural surfaces. The symmetry can
be understood most clearly by a comparison of figure 4, a lateral view
with figure 2, which is a view from the glandular surface, and with
figure 3, which is drawn from the neural surface.

THE EGG AND MIRACIDIUM OF SCHISTOSOMA JAPONICUM

The egg and miracidium of Schistosoma japonicum are smaller than
those of S. mansoni or S. haematobium (cf. figs. 4, 6). The eggs of
S. japonicum from the two eases which I studied showed no trace of
the rudimentary spine which is so often found on the eggs of this
species.t The most characteristic form of this spine is described by
Leiper (1911, p. 134) as follows:

In many of the ova the spine appears to rise from the center of a slight
navel-like depression in the egg shell. The base of attachment is thickened in
all and spreads out upon the shell for a short distance in a manner somewhat
similar to the attachment of a thorn to the stem of a rose.

Leiper examined about fifty eggs in all from seven different cases,
four in man and three in dogs, and came to the conclusion that the
presence of a rudimentary spine is a specific character. Katsurada

1JIn a sample of feces obtained recently from another case of Japanese

schistosomiasis about fifty per cent of the eggs showed no spine, while the rest
showed it in varying degrees of development.

1919] Cort: Eggs and Miracidia of Human Schistosomes 515

(1913, p. 370, figs. 4, 6, 7) found either a spine or a thickening of the
shell in all the eggs which he examined, and concluded that it was a
constant feature. Looss (1911), in the examination of an extensive
series of eggs to determine whether the rudimentary spine is a constant
feature, found all degrees of variation and a considerable percentage
of eggs in which no spine was present. He therefore concluded that
the presence of this spine is a variable feature and not a specific
character. Wooley and Huffman (1911, p. 131), in examinations of
several hundred eggs of S. japonicum, found in no instance the least
appearance of a blunt protuberance or spine on the outer envelope

Fig. 5. Microphotograph of miracidium of S. japonicum just after it has
escaped from the egg. Photographed by Dr. J. P. Hickey.

of the egg. These observations suggest that the lateral spine of the
ova of S. japonicum is variable and cannot be considered as a specific
character. The surface of the shells of the eggs of this species which
I examined appeared to be covered with some sort of a sticky sub-
stance. This is shown by the fact that the egg never showed a clear-
cut outline as in S. mansoni (fig. 1), but always had particles of
débris adhering to it (fig. 5).

When eggs were first examined fresh from the feces the miracidia,
which at this time completely filled the shells, were practically
motionless. After a few hours in fresh water the egg shell expanded,
leaving a considerable space between the shell and the miracidium,
which at this stage was moving actively. In this space were collected
granules and oil globules. The globules of oil were extruded from

516 University of California Publications in Zoology — [ Vou. 18

the anterior ducts (fig. 6, ad) which open on each side of the body
between the so-called cephalic region and the body proper. The
internal relations of these ducts were not clear, but extrusion from
them of the oil globules was observed both in S. japonicum and S.
manson. Holeomb (1907, fig. 3) figures the anterior ducts in SV.
mansoni as if connected with the cephalic glands. My studies gave
no evidence of this relation.

O.OS5 mm.

Fig. 6. Miracidium of S. japonicum within the egg, from glandular surface;
letters as in figures 2 and 4. The reference line from cg is incorrectly drawn.
It should be extended to the cephalic gland on the left side.

The exact process of the hatching of the egg I did not follow, nor did
I see the miracidium escape. The remarkable microphotograph shown
in figure 5 was taken by Dr. J. P. Hickey and I am much indebted
to him for its use. In the photograph the split through which the
miracidium has just escaped is across the end of the egg. The process
of hatching of the embryo from the egg has been described for SN.
haematobium by Seligmann (1898, pp. 386-388) and by Conor (1910,
p. 533). Smith (1911, p. 64) described this process for the egg of
S. japonicum. The accounts agree with my observations in that the
egg shell begins to swell soon after the egg is placed in water and

1919] Cort: Eggs and Miracidia of Human Schistosomes BLT

the miracidium becomes active, often turning completely around.
Finally the egg bursts by splitting, allowing the miracidium to escape.
The bursting of the shell seems to be due to the swelling caused by
the action of the water and not by any activity of the embryo. I
will quote Smith’s description (1911, p. 64) of the hatching of the
egg of 8S. japonicum:

The specimens shown [eggs of S. japonicum] are in the early unexpanded
state. At about 30° C, in the course of ten to twenty hours these eggs expand
to nearly or quite double their capacity and the miracidium, now in the
quiescent stage, moves actively about within the enclosure and with further
enlargement, the wall of the ovum splits and the embryo escapes, a free-
swimming ciliated organism.

Fig. 7. Diagrammatic representation of one side of the excretory system of
the miracidium of S. japonicum, from the lateral view; bt, bladder tubule; c,
capillary; exp, excretory pore; f, flame cell.

The freed miracidium in the microphotograph (fig. 5) shows cer-
tain of the structural characters very clearly. The anterior region is
somewhat contracted. The non-ciliated anterior papilla shows very
clearly at the anterior tip. A short distance back from this, are visible
the depressions which mark the openings of the anterior ducts and
near the posterior end the openings of the excretory pores are also
marked by depressions. Some idea can also be gained of the character

518 University of California Publications in Zoology [ VoL. 18

of the glandular structures of the anterior end and the germ cells near
the posterior end.

The cephalic glands in the miracidium of Schistosoma japonicum
are smaller in proportion to the length of the body than in S. mansoni
(ef. fig. 2, cg; 4, eg). Also fewer germ balls are present in the posterior
body region than in the miracidium of S. mansoni. The figures of
both miracidia represent optical sections and therefore cannot show
the total number of germ cells or their exact relation.

The excretory system of Schistosoma japonicum is shown in figures
6 and 7. Exeretory pores are located near the posterior end on each
side (figs. 6, 7, exp). The two sides of the system are entirely separate.
From the pores on each side the main tubules coil backward and then
forward and again back to the points on each side where they receive
the capillaries from the flame cells (figs. 6, 7, f). The capillaries of the
flame cells are of distinctly smaller caliber than the main tubules.
The positions of the flame cells'are shown in figure 6.

Looss’s descriptions and figures (1893, p. 189) of the excretory
system of the miracidium of Schistosoma haemotobium differ in two
particulars from the above description of this system in S. yaponicum.
Looss showed all the tubules of the same caliber. He also figured the
capillaries of the posterior flame cells as much shorter than those of
the anterior flame cells.

1919 | Cort: Eggs and Miracidia of Human Schistosomes 519

LITERATURE CITED

Conor, A.
1910. Quelques particularités biologiques du miracidium de Schistosomum
haematobium. Bull. Soc. path. exot., 3, 533.

Houcoms, R.
1907. The West Indian bilharziosis in its relation to the Schistosomwm man-
soni (Sambon, 1907); with memorandum in ten cases. U. 8. Naval
Med. Bull., 1, 55-80, 4 figs. in text.

KATSURADA, F.
1913. Schistosomiasis japonicum. Centralbl. f. Bakt. Parasit. u. Infek., 1.
Abt. Orig., 72, 363-379, pls. 1, 2.

LEIPER, R. T:
1911. Note on the presence of a lateral spine in the eggs of Schistosomum
japonicum. Trans. Soe. Trop. Med. Hyg., 4, 1383-135, 1 pl.

Looss, A.

1893. Beobachtungen tiber die Eier und Embryonen der Bilharzia, in
Leuckart, Parasiten des Menschen, 2. Abt., pp. 521-528, 2 figs. in
text.

1896. Recherches sur la faune parasitaire de l1’Egypte. Mem. Inst. Egypt,
3, 1-252, pls. 1-16.

1911. Some notes on the Egyptian Schistosomum haematobium and allied
forms. Jour. Trop. Med., 14, 177-182, 2 pls.

SELIGMANN, C. G.
1898. Observations on the hatching of the ova of Bilharzia haematobium.
Trans. Path. Soe. London, 49, 386-388.
SmiTH, A. J.
1911. Ova of Schistosomum japonicum; ova of S. mansoni; ova of Paragoni-
mus westermanti. Proce. Path. Soe. Phila., n.s., 14, 64.
Woo.Liey, P. G., AND HuFFMAN, O. V.

1911. The ova of Schistosoma japonicum and the absence of spines. Para-
sitology, 4, 131-132.

par

22.
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DALES 18-200 March, 24096 ox nee ota ee eee es. ea ade aed een seen ee

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. Distribution of Land Vertebrates of Southeastern Washington, by Lee

Raymond Dice. Pp. 293-348, plates 24-26.. June, ~1916 0... o ocean
The Anatomy of Heptanchus maculatus: the Endoskeleton, by J. Frank
Daniel. Pp.:349-370, pls. 27-29, 8 text figures. December, 1916 ._.22........
Some Phases of Spermatogenesis in the Mouse, by Harry B. Yocom. Pp.
S71-3807 piatec30..” January, 1987 sen ee re ee Se ee
Specificity in Behavior and the Relation between Habits in Nature and

-. Reactions in the Laboratory, by. Calvin O. Esterly. Pp. 381-392. March,

Ba LS 8 BY SERED sop sh aad mace, er gan PRA eg PURPA NARI Ar RAPER As UPR Sana ee A

. The Occurrence of a Rhythm in the Geotropism of Two Species of Plank-

ton Copepods when Certain Recurring External Conditions are Absent, by
Calvin’ O.:esterly.: Pp; 393-4005" March;d917 92s.
On Some New Species of Aphroditidae from the Coast of California, by
Christine Essenberg. Pp. 401-430, plates 31-37. March, 1917 ..2..2.........-..
Notes on the Natural History and Behavior of Emerita analoga (Stimpson),
by Harold Tupper Mead. Pp. 431-438, 1 text figure. April, 1917 ........... di
Ascidians of the Littoral Zone of Southern California, by William E. Ritter
and Ruth A. Forsyth. Pp. 439-512, plates 38-46. August, 1917 ........22202.
Index in preparation.
Diagnoses of Seven New Mammals from East-Central California, by Joseph
Grinnell and Tracy I.-Storer. Pp. 1-8.
A New Bat of the Genus Myotis from the High Sierra Nevada of Cali-
fornia, by Hilda Wood Grinnell... Pp. 9-10.
Nos. 1 .and 2 in one cover, August,- 1916 <5. occ ooo. celccce osc ecneccecsceecenenes
Spclerpes platycephalus, a New Alpine Salamander from the Yosemite
National Park, California, by Charles Lewis Camp. Pp. 11-14. Septem-

RARE ik Rl a a ea ec rh eg acces Os aarp

. A New Spermophile from the San Joaquin Valley, California, with Notes

on Ammospermophilus nelsoni nelsoni Merriam, by Walter P. Taylor. Pp.
15-202. fours i text OCtaper: TOE G 5a ee a, cats cap cncnateaewcavemngeeoan
Habits and Food of the Roadrunner in. California, by Harold C. Bryant.
Pp. 21-58, plates 1-4, 2 figures in text. October, 1916 .........-.....4....--4.--.---
Description of Bufo canorus, a New Toad from the Yosemite National Park,
by Charles Lewis Camp. Pp, 59-62, 4 figures in text. November, 1916...
The Subspecies of Sceloporus occidentalis, with Description of a New Form

from the Sierra Nevada and Systematic Notes on Other California

Lizards, by Charles Lewis Camp. Pp. 63-74. December, 1916 _..................

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18.
14.
15.

16.
17.
18.

VoL is. 1.
2.

4,
5.

15.

Vol. 21. 1.

. A Quantitative Analysi

UNIVERSITY OF CALIFORNIA PUBLICATIONS— (Continued)

Osteological Relationships of Three Species of Beavers, by. F. ‘Harvey “2

Holden. Pp. 75-114, plates 5-12, 18 text figures. March, 1917 ...0...c.c..
Notes on the Systematic Status of the Toads and Frogs of California, by
Charles Lewis Camp. Pp. 115-125, 3 text figures. February, 1917 ...........

A Distributional List of the Amphibians and Reptiles of California, by.»

Joseph Grinnell and Charles Hewils Camp, Pp. 127-208, 14 figures in text.
GUY PONT FS se eS oie ee eee suian 2Or kates Jee Nea ere

A Study of the Races of the White- Fronted Goose (Anser albifrons) Occur-
ring in California, by H. S. Swarth and Harold c. Bryant. Pp. 209-222;°

2 neures instext, plate-1S October, 1900 so a a
A Synopsis of the Bats of California, by Hilda Wood Grinnell. Pp. 223-404, ;
plates 14-24,.24 text figures. January 31, 1918. 22200
The Pacific Coast Jays of the Genus ‘Aphelocoma, by H. S. Swarth. Pp.
405-422, 1 figure in text. February 23, 1918 ..cccccc.-n-cccccccolecceccsstecsecectcenecocced

Six New ‘Mammals from the Mohave Desert and Inyo Regions of California,
by Joseph Grinnell. Pp. 423-430.
Notes on Some Bats from Alaska and British Columbia, by Hilda Wood
Grinnell, Pp. 431-433.
Nos. 14:and:15 in one cover. April, 1918 2.0.

Revision of the Rodent Genus Aplodontia, by Walter P. Taylor. Pp. 435-

504; plates 25-29, 46° text. figures: May, 1918) 023230 oe ee,

The Subspecies of the Mountain Chickadee, by Joseph Grinnell. Pp. 505-

5t5: 3. textiMenres; s WEA ys EO UB er se oe a pire de ote te a

Excavations of Burrows of the Rodent Aplodontia, with Observations on

the Habits of the Animal, by Charles Lewis Camps Pp. 517-536, 6 figures

yo Go + sg open £1 be - Wan ASS By, ea ae bag en Oe aw RGM Reach lats SA Ria SN A A ONC a Set
Index in preparation.

Mitosis in Giardia microti, by William C: Boeck. Pp. 1-26, plate 1. Octo-
j iT) ede’ bo By cago Geet 7 ate SRR ae of uetea ues es INTO Sel en Gctita A nea TR OR EE CRORE we
An Unusual Extension of the Distribution of. the Shipworm in San Fran-
cisco Bay, California, by Albert I. Barrows. Pp. 27-43. December, 1917.
Description of Sonmie New Species of Polynoidae from the Coast of Cali-
fornia, by Christine Essenberg. Pp..45-60, plates 2-3. October, 1917 -.....
New Species of Amphinomidae from the Pacific Coast, by Christine Essen-
berg. Pp. 61-74, plates 4-5. October, 1917 2... cccces lie ceeendccceetcacdtcccentesent
Crithidia euryophthalmi, sp. nov., from the Hemipteran Bug, Euryophthalmus
convivus Stal, by Irene McCulloch. Pp. 75-88, 35 text figures. Decem-
Wet POLL Sch Seka el arc ei ers DS Gi eT 2 ea
On the Orientation of Erythropsis, by Charles Atwood Kofoid and Olive
Swezy. Pp. 89-102, 12 figures.in text. December, 1917 .-.0.2...c0ce ee

. The Transmission of Nervous Impulses in Relation to Locomotion in the

Earthworm, by John F. Bovard. Pp. 108-134, 14 figures in text. January,
a ROS 2 PRM pe eRe tc oes MEER Salk eS aie ie tN NPN Feeder nc AME LW Ug DNR ROR Yaad: he eee
The Function of the Giant Fibers in Earthwotms, by John F. Bovard. Pp.

185-144,' 1) figure. in text.; | Jannary; 19182 sis eS

A Rapid Method for the Detection of Protozoan Cysts in Mammalian
Faeces, by William C. Boeck. Pp. 145-149. December, 1917.20.20
The Musculature of Heptanchus maculatus, by Pirie Davidson... Pp. 151-170,

12 figures in. text. March, 1918 «..... Se agit ce YC a oh etn eo
The Factors Controlling the Distribution of the Polynoidae of the Pacific

Coast of North America, by Christine Essenberg. Pp. 171-238, plates 6-8,
2 figures: in-text. March lol 822 5 a eine rapes! een bees

. Differentials in Behavior of the Two Generations of Salpa democratica
Relative to the phe ole of the Sea, by Ellis L. Michael. Pp. 289-298, ©

plates 9-11, 1 figure dyietoxh... March: TOTS 3-2 Fes ok eos
8 of: the Molluscan Fauna of San Francisco Bay, by
BE. L. Packard. Pp. 299-336, plates 12-13, 6 figs. in text. April) 1918...

. The Neuromotor Apparatus of Huplotes patella, by Harry B. Yocom. Pp.

837-396, plates 14-16. September, 1918 2)... ce eee
The Significance of Skeletal Variations in the Genus Peridinium, by A. L.
Barrows. Pp. 397-478, plates 17-20, 19 figures in text. June, 1918 2.0.0.2.

. The Subclavian Vein. and its Relatiens in Elasmobranch Fishes, by J.
Frank Daniel... Pp. 479-484, 2 figures-in text. August, 1918 2.00 ..
. The Cercaria of the Japanese Blood Fluke, Schistosoma Japonicum Kat-

stirada, by William W. Cort. Pp. 485-507, 3 figures. in text.

. Notes on the Eggs and Miracidia of the Human Schistosomes, by William

W. Cort. Py, 509-519, 7 figures in text.
Nos, 17 and) 18: incene: covers danuary: 1019. fos re ea dee
A Revision of the Microtus Californicus Group of Meadow Mice, by Rem-
ington Kelloggs. Pp. 1-42, 1 figure in text. December, 1918.20.02...

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