faite
fe
ee

5
Reh §
oy
A

pet
Pee tyts
Cova)

W

The person charging this material is re-
sponsible for its return to the library from
which it was withdrawn on or before the
Latest Date stamped below.

Theft, mutilation, and underlining of books
are reasons for disciplinary action and may
result in dismissal from the University.

UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN

L161— 0-1096

Digitized by the Internet Archive
In 2011 with funding from
University of Illinois Urbana-Champaign

htto://www.archive.org/details/morphologyofostr21kesl

ITY OF ILLINOIS

TAS

ILLINOIS BIOLOGICAL ‘MONOGRAPHS is a general title ‘somnreite tae a ce
of monographs on subjects in botany, entomology, zoology, and. allied fields. Hac
is an independent publication. For the convenience of bibliographers and librarians,
year’s output is called a volume. Each volume consists of approximately 450 pages, pri
at four dollars. A volume may consist of two, three, or four individual monographs. -
of individual numbers are indicated in the Tee of titles given below. Requests for exchanges 4
should be addressed to the Exchange Department, University of Illinois Library, Urbana, —
- Ilimois. All communications concerning sale or subscription should be Bape lees to the
Director, University of Illinois Press, Urbana, Illinois. sate

seat Vol. I
Nos. ‘Le. A Revision of the Cestode Family Proteocephalidae. With 16 plates. By en Res
La Rue, $2.00. is
No. 3. Studies on the Cestode Family Anoplocephalidae. With 6 plates. By H. Douthitt,
80 cts. .

No. 4. Some North American Larval Trematodes. With 8 plates. By W. W. Cae $1.20.

Vol. II : oe
No. 1. Classification of Lepidopterous Larvae. With 10 ee By 8. B. Fracker. $1.50.
No. 2. On the Osteology of Some of the Loricati. With 5 plates. By J. E. Gutberlet. 50 cts.
No. 3. Studies on Gregarines. With 15 plates. By Minnie E. Watson. $2.00.
No. 4. The Genus Meliola in Porto Rico. With 5 plates. By F. L. Stevens. (Out of print.)
; Vol. Til
No. 1. Studies on the Factors Controlling the Rate of Regeneration. By C. Zeleny. $1.25.

1
No. 2. The Head-capsule and Mouth-parts of Diptera. With 25 plates. By A. Peterson. $2.00.
3. Studies on North American Polystomidae, Aspidogastridae, and Paramphistomidae.
With 11 plates. By H. W. Stunkard. $1.25.
No. 4. Color and Color-Pattern Mechanism of Tiger Beetles. With 29 black and 3 colored
plates. By V. E. Shelford. $2 00.

Vol. IV

. Life History Studies on Montana Trematodes. With 9 plates. By E. C. Faust. $2.00.

No. 2. The Goldfish (Carassius carassius) as a Test Animal in the Study of Toxicity. By E. B.
Powers. $1.00.

No. 3. Morphology and Biology of Some Turbellaria from the Mississippi Basin. With 3
plates. By Ruth Higley. $1.25.

No. 4. North American Pseudophyllidean Cestodes from Fishes. a 13 plates. By AR

Cooper. $2.00.

2
°

Vol. V
No. 1. The Skull of Amiurus. With 8 plates. By J. E. Kindred. $1.25.
No. 2. Contributions to the Life Histories of Gordius robustus Leidy and Peragordius varius

(Leidy). With 21 plates. By H. G. May. $1.50. .
Nos. 3-4. Studies on Myxosporidia. A Synopsis of Genera and Species of Myxosporidia. With
25 plates and 2 text-figures. By R. Kudo. $3.00.

Vol, VI

No. 1. The Nasal Organ in Amphibia. With 10 plates. By G. M. Higgins. $1.00.

Nos. 2-8. Revision of the North American and West Indian Species of Cuscuta. With 13
plates. By T. G. Yuncker. $2.00.

No. 4. The Larvae of the Coccinellidae. With 6 plates. By J. H. Gage. 75 cts. (Out of print.)

[Continued inside back cover]

The Morphology of Ostracod Molt Stages

as

ose

The Morphology
of Ostracod Molt Stages

BY ROBERT V. KESLING

ILLINOIS BIOLOGICAL MONOGRAPHS: Volume xx1, Nos. 1-3

THE UNIVERSITY OF ILLINOIS PRESS
URBANA, 1951

Copyright 1951 BY THE UNIVERSITY OF ILLINOIS PRESS. MANUFACTURED
IN THE UNITED STATES OF AMERICA. Board of Editors: HARLEY JONES
VAN CLEAVE, WILLIAM R. HORSFALL, AND LELAND SHANOR

NM. SMITH

JUN 191951

JAI

TIE.

1g

Contents

onda CDG PLO NimeMen pater atc cele pte © 24 Gis la. oo Ske sven LER Pees OEE ae vs
TARO NGM MEG e he Siac. Re Wee and Raha oy on ee leah eee ews
GHNERACMONSCREPTION |. sa/csaig feo fee S agtente cab see cee eee Bacneaanes
Odie CTE TAM OMGe a e% rss Sense saa ak cals ed odie Ws Sea SA aaa
Cae CTO rate ne oo ce rae fanaa ts. alain nt oa des twokad
Min onseies eC1OM ia ue aa Gh smeinales satan ie Gad pelo dala a Rass
Wigestive wy stem and Glands iiss Se eiwin ew vin viedo pind eroaete vg de ees
DET MED UE SCRIPTION. Siqgkehen did don ehbulan eda cada dail o«@adecdds as
PNM CUMUNCS Benne te ch fed @ atin eens a a eee vin wees See Sacer
FAMD GUC WORM, Puce erat nee hate thai aly Sara ede ne ae
JUL ae Uh 6) (aOR Pea ear Gre a ye ea ce re ear era ere
Honeheac ater Uipper dip. 2.4 2.e few oe ohh oe whe mee Sha ee ess
EL IOOSCOMNE! cae Dives dia et aye ey ee awe be baw hee ouk Panels
PlillnGan ty Gee enema nie erie eR Paco eaters Se neo ee vals
iret NORACIG Auelen ovary tas ceteaa sae sd Mites a Ses Ge eae
Become LNOFACIC: OPS ne we eos enue aes so see estas
Minds POraciG)e@s. 2.5.0.44 aedic we eh ees scans = aio ees awe

LDTAC2 1c ee Nap ea Ours age Sea ea aa ae ee Pe A a
a AE rete ee ee te, hans eal oe ede dards
EMG Oshe COM et miner eect ene ee Shiny Sao wats Ae 2
Excretory Gland A—the Gland of the Antennule..............
Excretory Gland B—the “Shell Gland”.....................--
Excretory Gland C—the Maxillary Gland.....................
he Liver or Hepatopancress: <4 cicascseceunsedaesex seconds
Gland L—the Gland of the Upper Lip........................
“Gland M’—the Gland (?) of the Mandible..................
Gland N—the Gland of the First Thoracic Leg................
Gland Othe Copulation: Gland osc: s.2s¢0ubes 25 2eaded seeds
he ADimestive ss Vstein aves dn cont eee ae beet eae ne eee mes
ie: Nerv OMS eV cleily 4. sna ee as bab ee weds eae es
ESN VCR recite, aire tare ee tees wabikl o PCy doh aS nib audi Bea HEC a ae
The Epidermis or Hypodermis. t5./<..cusauieascaswaeeads obs
Hard Parte O00 the: V alvesed cad tencibwtaenws de Deeds eh ened 5
X-Ray Diffraction Study of the Ostracod.....................
DOCTEUOM (Ok. GE OMCs cierto ces ane os eave wy ote oo Wl S:Ghe foie e decd ORs
he Cosine Isles" waco an oye uae ee Ca oe ee wale claw wine w
PVCS pie GOEL sly pe heige teow ae eee ie WR oe eb 6. Bhan. Each, ear enk
ReproduniiverSVSteMin. . och atcec <p cee ode Sees adeeb eeae ae
BIQUOGN ayesha eee eee ie ee ee ee ee hehe tomes
The Egg and Embryonic Development.....................-.
“he: Process: 01 “ig? a vine. occas vanes anc fie bea ee aG seer as
The: Process’ of, Molting. 0.0.6 ch cen bee can we csiee es Seeeunwns

oy

54
D0
56
56
57
59
60
61
64

V;

Vil

Vi:

VIII.

SWLMNITO s cs feieacs eens oe he eure beter uteders che cy ne cee 83

Walkie sco onc oP Ree ee oe Bile @ od Sb gee Sate gn oes S4
pH. Volerances:, 3). te cssc aati ae ace. wae a ete oe eye S4
Heat and Cold- Tolerantet.o2:.60.i400. 046004 .0 ea eee 85
Relation of Heat and (Growth. «0... <6. ss 4geu, 22 eee S7
PHOGOtARIS su) Ss ge Se ess 4 oes wie ee ai wre 4 den a ee S7
Relation. of Light: and Growth. . «2... d0+ «lal «ane eeeeee SS
Rate of Reproduction and Life Spam... ...... 0108: seskaneeeeee 89
ROO oni Solna eee ecm aaek Hoel Beek Sn0.4 om dee eee 91
Commensalism im Ostracods:. .< 06.0.0 i os bs on as Sern shee 92
Parasites of “OStracods: soc ..cccse ses seaees = ony ge Oe 92
EMMATURE STAGES. cas ivacda oct ecd ea se dkae dep oes es wee 94
First IMGtar 024 sie atcc hoe alles sia oes et uaay teee a sane een 95
Second Instat Ss on ees nace) oak Oe a cae ce cerrnn aie te caeLe ee eee 96
Wl Gace Ua Cc = rh a a ee NE er OM OUR EWS 97
Fourthalvictar 5 a sk.a.c epee ukere fae aaa e 4 pe ee ee es Coenen 97
PEGI TNS Ga es eek tn cca sate wel ace ark, Sic eee eae ae eee 98
SIEM INSEAT sare cas re Ue ee ce Smee eh ee oe re ee eee 98
Devemth lnstar aol s esaiee ntact eee ee eaee ee elas ete mci 99
Ritohth instars cetacean G oxen aa ne eos so omrle aie ee eens 100
DG VNC acis ees tye ao horse asics et ieee ae a cree cae eens 100
VARIATIONS. IN SIZE OF INSTARS. 24..[. 2 sce e.e sate ca eu sega oe eee etree 101
Brooks! Psa We eect eee een cade Pte etch a este cere eee 101
VARIATIONS IN SHAPE OF INSTARS.......... 000 cee e eee e eee eee tees 103
SRIOM@ AION so. caw aths ane patos swab eo ewan eae aces Beene 108
SWINGING SS 4 Smee, Ceara eter Se ieee oust shea ane ved gee ee oe 104
oT FROMMCMESS ai, vis Meast esc iciais: B Brew Nts wl Rlacs eM ate Le & eto eee eee 104
Applications of Huxley’s Constant Differential Growth-Ratio
PAG st2 <, We a. ahd seca ececa wy we alec ae Re ware PAS a uae 105
D’Arey Thompson’s Graphic Expression of Growth-Gradients
Applied: to: Valves: of Imstars i532 nce aed o5c5 Seeeeee pecans 107
Schmalhausen’s Formula Applied to Valves of Instars.......... 107
RELATION OF APPENDAGES AND INTERNAL ORGANS TO THE SHAPE OF THE
VATIVES: IN: TINSTARS nie oGsstidontls « qe-clsi nits da uQvercpe nds dace eee oe 110
First to second =I nstarases waa 2sa< tees eb ein Bees eee ASE
Second to. hind dmstarse | ascent ar cen ens avd ccs kaehew ie eure are Pt
Third tock OurthsInctate< as Gcoen ed eawam oat Oke ba ade aon 111
Hourth: toc Pik thilnistatscnr ta twat Dre Be viedo ae oak: oedeeene nee 112
Pitth: t65Sixth Instat orci es oss wet se eo ewegs oyu eae eee 115
Siccth how Me Were LES Mises tote ina aarta. ane waste ote arin so age ee eo ae alah)
Seventh tor Haghth Unstar.: «Ac .cac0 Space nwa ke eee ieee ores ee 113
Bighth--to. Nmtins Wistar sz sesh c Peete shacks nso tals ake bless tee eee 114
HEIGHT-LENGTH RATIO AS A VALID CHARACTER FOR DETERMINATION OF
SPH CURIS as vos cen cos a cuca se as oy eos RL oer a eh Laeger 115
BIBITOGRAP EY 2 c, Beta dl cctien eco RE aed cree eee eae 117
PLATES <, = ahs Gisicortldcs odaty weet adhe a Goa Da Rus aegis ae enna owe saeentnen 127
|G 0 10, Geet an nem PRI Te SO EIR SA reer 321

Introduction

Recent oil explorations have increased the importance of micropaleon-
tology, which can be used to determine the stratigraphic sequence in
many cases. Ostracods are now being used as stratigraphic markers, and
their use will be increased if greater taxonomic accuracy can be obtained.
The small size of the animal, less than one millimeter in length in most
species, permits whole faunas to be secured from well cuttings and well
cores. Ostracods are also prolific in many formations, so that relatively
small amounts of material are necessary to obtain abundant specimens.
The hard parts are well preserved, even in many highly indurated and
folded strata.

The ostracods have a long geologic range, so that additional informa-
tion on the zoology, biology, and ecology of the animal can be applied to
a large number of genera occurring in many formations. Further, the
value of the ostracod is increased by its adaptation to fresh-water en-
vironments as well as marine.

Much of the taxonomic work on fossil species has been done by paleon-
tologists who understood very little about the nature of the living animal.
Conversely, much of the classification of living species has been done by
zoologists with little or no knowledge of fossil forms or the geologic his-
tory of the order. The result has been two systems of classification, the
one based on the size, shape, and ornamentation of the shell and the other
on the finer details of the appendages. This impasse has even reached a
point where a single specimen is classed as one genus by the paleontolo-
gists and another genus by the zoologists.

Although much taxonomic work on fossil and living ostracods is being
done in the United States, there is not an adequate description of an os-
tracod in the English language. One of the best available descriptions is
given by Hoff (1942, pp. 41-49), who found it imperative to devote a sec-
tion of his taxonomic work to the morphology of fresh-water ostracods
so that his systematic work could be more fully understood. Most of the
morphological work on ostracods was done by German workers between
1854 and 1926. A recent monograph by Dom Remacle Rome (1947), a
French worker, gives some additional facts about ostracod structures.

The incomplete knowledge of the ostracod has caused some important
paleontological questions to remain unanswered. Many structures, such
as the so-called brood pouch, are found on fossil forms and not on living
ones, and there is no adequate explanation of their function or signifi-

[ vii ]

vill INTRODUCTION

cance. Indeed, there is even a question in many fossil species as to which
end of the shell is anterior and which posterior, and it 1s quite possible
that the dorsal and ventral orientation has been reversed in some in-
stances. Where the specimens are scarce in a formation and vary in size,
it is problematical whether the small specimens are adults of a small
species or only instars of a larger species. At the present time there is no
way of determining from a single specimen what instar is represented.
Another problem arises from the differences in shell shape and size due
to sex differences. It is known from living species that there are greater
differences between the male and the female of one species than between
females of different species, and the determination of sex in fossil forms
is largely conjecture. These are only a few of many unanswered problems
in micropaleontology.

The writer chose Cypridopsis vidua O. F. Miller as a living species for
investigation because it has several characteristics advantageous to a
complete study. It belongs to the family Cypridae, which has both fresh-
water and marine species. The genus Cypridopsis is reported back as far
as the Pennsylvanian period by Scott (1944, p. 144). The species vidua is
geographically widespread and has been reported from North America,
Paraguay, northern Africa, Europe, western Russia, and the Azores.
Furthermore, it is adapted to a variety of environments, including moun-
tain lakes, brackish water, streams, lakes, and ponds. It is abundant in
many locations. This common ostracod is easily cultured for laboratory
observations. Cypridopsis vidua reproduces parthenogenetically, and the
lack of any males insures that all immature instars are of the same sex.

The study of this species has been designed to give a full description of
a typical living ostracod, some pertinent biological information, and a
comparison of the valves of the various instars.

The writer wishes to acknowledge the kind assistance and guidance of
Dr. Harold W. Scott of the geology department and Dr. Harley J. Van
Cleave of the zoology department of the University of Illinois. The micro-
tome sections were prepared by Miss Marion Birkner under the direc-
tion of Dr. Van Cleave. The X-ray pattern of the shell material was
made by Mr. Karl Koenig. The work was done while the writer held fel-
lowships from the Shell Oil Company (1947-48) and the California
Company (1948-49).

L. ‘Taxonomy

OrDER OSTRACODA LATREILLE

Latreille (1802, p. 17) was the first to use the term Ostracoda, which
he originally spelled “Ostrachoda.” However, he included genera of both
Ostracoda and Cladocera under this designation.

Straus (1821, p. 58) was the first to set up a group to include the genera
which we now consider ostracods. He termed this group Ostrapodes, as set
aside from the Cladocera also included in Latreille’s Ostracoda. Since
this is the first term applied to this group of organisms, they should by
rules of nomenclature be called Ostrapodes. Since the term Ostracoda has
been accepted for such a long time, it is doubtful if it will ever be re-
placed by the rightful designation.

The common German name for the ostracods is Muschelkrebse, and
Johansen (1921, p. 88) suggested the English equivalent ‘‘mussel-
shrimps,” but the usage has never been widely followed.

The ostracods are characterized by having a dorsally hinged bivalved
shell and at most only five pairs of post-oral appendages: maxillae; first,
second, and third thoracic legs; and the fureae (which are often not
classed as appendages). The shell has no growth lines, which distinguishes
it from the shells of certain phyllopods (Conchostraca) and certain small
mollusks (Sphaeriidae).

Famity CYPRIDAE ZENKER

In this family of ostracods all the thoracic legs are different, the exo-
podite of the antenna is greatly reduced, and the teeth of the hinge are
greatly reduced. The surface of the shell is usually smooth. The anten-
nules and the antennae are usually equipped with long natatory setae.
The first thoracic leg is modified as an auxiliary feeding structure.

SUBFAMILY CYPRIDOPSINAE
Shell high and short, 1 mm. or less in length. Antenna of five podomeres.
Outer “masticatory” process of the maxilla with two strong setae. Third
thoracic leg with distal pincers arrangement. Furea reduced to a base
ending in a long seta or “‘flagellum.”’

GENus CYPRIDOPSIS Brapy 1867
Shell tumid; valves approximately the same size. Natatory setae of the

antennules and antennae well developed. Terminal podomere of the max-
illary palp longer than wide.

[1]

2 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

Brady and Norman (1896, p. 725) proposed the genus Pionocypris for
ostracods of this description having the left valve overlapping the right
anteriorly and posteriorly, and restricted the genus Cypridopsis to those
species having the right valve overlapping the left. The genus Pionocypris
has not been generally accepted. The writer has not examined other
species of Cypridopsis (as used here), many of which are limited to
Europe; so he does not offer an opinion on the validity of Brady and
Norman’s genus and follows the generally accepted use of the genus
Cypridopsis.

CYPRIDOPSIS VIDUA (O. F. Mtuuer 1776) Brapy 1867

Cypris vidua O. F. Miiller 1776. O. F. Miiller, 1776, p. 199; Miiller, 1785,
p. 55; Zaddach, 1844, p. 35; Baird, 1849, pp. 152-53; pl. 19, figs. 10-
11; Zenker, 1854, p. 79; Chyzer, 1858, p. 512; Claus, 1868, p. 151,
pl. 1, figs. 6-8; Fri¢é, 1872, p. 227, also called Gestreifter Muschel-
krebse, Lasturnatka zihovana; Chambers, 1877, p. 155; Underwood,
1886, p. 337.

Monoculus vidua (O. F. Miller 1776) Jurine 1820. Jurine 1820, p. 175.

Cypridopsis vidua (O. F. Miller 1776) Brady 1867. Brady, 1867; Herrick,
1887, p. 31; Sars, 1890, p. 17; Vavra, 1891, pp. 75-77, fig. 23; Richard,
1896, p. 173; Turner, 1896, pl. 5, fig. 13; Kaufmann, 1900 a, p. 107;
G. W. Miller, 1900, pp. 80-81; Sharpe, 1908, pp. 990-91; Daday,
1905, p. 252; Cushman, 1907, pp. 37-38; Kofoid, 1908, p. 258; Vavra,
1909, pp. 114-15; Fowler, 1912, pp. 72-73; Weckel, 1914, p. 179;
Wohlgemuth, 1914, p. 16; Sharpe, 1918, p. 807, fig. 1253; Wolf, 1919,
p. 44; Korschelt, 1920, p. 73; Herr, 1921, p. 15; Klugh, 1921, p. 73;
Schreiber, 1922, p. 493; Bronnstein, 1924, p. 82; Reed and Klugh,
1924, p. 274; Bronnstein, 1925, pp. 3, 6, 16; Holmes, 1937, p. 492;
Graf, 1940, p. 486; Klie, 1940, p. 61; Redeke and Dulk, 1940, p. 1438;
Hoff, 1942, p. 151; Hoff, 1943a, p. 53; Hoff, 1943b, p. 117.

Cypriodopsis |sic| vidua (O. F. Miller 1776) Ferguson 1944. Ferguson,
1944, p. 719.

Cypridopsis vidua vidua G. W. Miiller 1912. G. W. Miller, 1912, p. 210;
Furtos, 1936, p. 491, Dobbin, 1941, pp. 230-31.

Cypridopsis vidua obesa Towle 1900. Towle, 1900, p. 347; G. W. Miiller,
1912, p. 210; Furtos, 1933, p. 431.

non Cypridopsis obesa Brady and Robertson 1870. Brady and Robertson,
1870, p. 15.

Cypridopsis vidua helvitica G. W. Miller, 1912. G. W. Miller, 1912, p.
210.

non Cypridopsis helvitica Kaufmann 1900. Kaufmann, 1900b, p. 310.

Cypridopsis pustulosa Furtos 1933. Furtos, 1933, pp. 431-32.

TAXONOMY 3

? Cypridopsis crassipes Masi 1909. Masi, 1909, pp. 372-74, pl. 12, fig. 8.

Pionocypris vidua (O. F. Miller 1776) Brady and Norman 1896. Brady
and Norman, 1896, p. 726; Norman and Scott, 1906, p. 113; Sawaya,
1942.

Pionocypris vidua vidua (G. W. Miiller 1912) Gauthier 1939. Gauthier,
1939, pp. 225-26.

Type Locality: Europe.

Description of the Adult Female: Shell smooth, ovoid. Greatest height
approximately two-thirds of the length, and located slightly anterior to
the middle of the shell. Shell tumid when viewed from above. The great-
est width a little more than the height, and located slightly posterior to
the middle of the shell. The ventral margin slightly sinuate in lateral
views. The surface marked by very minute depressions. Shell hairy,
particularly near the borders of the valves. The left valve slightly over-
laps the right anteriorly, posteriorly, and ventrally; very little over-
lap in the region of the hinge. The anterior margin of the right valve
equipped with fifteen to twenty tubercles, varying in size with individu-
als. The color of the shell pale green, yellowish green, yellowish white, or
pale yellowish brown. The shell marked by four bands of color varying
from light green to deep green, and even black in some individuals. The
color bands located in general: one anterior, one immediately behind the
eye, one slightly posterior to the middle, and one near the posterior end.

The bands extend from the dorsal margin down the sides of the
valves, and the location and size of these markings are variable. Some
individuals have bands so pale they can be seen only by transmitted
light. Individuals collected from the same locality show wide variations
in color and markings.

The natatory setae of the antenna extend beyond the terminal claws.
The exopodite of the first thoracic leg bears five setae. The outer “mas-
ticatory” process of the maxilla has two sharp, blade-like setae without
notched borders.

Length of the adult shell is approximately 0.65 mm.

II. General Description

Bopy SEGMENTATION

The structure of the ostracod has been profoundly influenced by the
development of an enclosing shell in the very early history of the order.
Apart from the appendages, the various structures of the animal do not
show close affinities with those of the higher Crustacea.

The compact, shortened body can be seen only after removal of one of
the valves of the shell. It has no true segmentation, although there is a
slight constriction of the body near the middle to mark the boundary
between the two regions of head and thorax. There is no abdomen. The
body tapers bluntly at the posterior end and terminates in a pair of pre-
anal furcae. There are seven pairs of appendages: the antennules, the
antennae, the mandibles, the maxillae, and three pairs of thoracic legs.
The first four pairs are attached to the head and are used chiefly for
swimming, walking, and feeding. The three pairs of thoracic legs are part
of the thoracic region and are adapted for feeding, creeping, and clean-
ing of the shell. The thorax also contains the genital regions.

The body of the ostracod occupies the middle two-thirds of the length
and is suspended from the dorsal region as an elongate chitinous pouch.
It is very deep and rather blunt at the anterior end, tapers slightly
throughout its length, and ends rather abruptly at the posterior end,
where the paired whip-like furcae are attached.

HEAD REGION

The head portion of the body has, in addition to the appendages, three
prominent features which are intimately connected with the arrange-
ment and operation of the appendages: the forehead, the upper hp, and
the hypostome.

The forehead and upper lip are closely connected. Both are formed of
a framework of chitinous rods with a continuous flexible chitin cover.
The forehead protects the median eye and provides sockets for the anten-
nules and antennae. It is narrowly rounded and forms the dorsal anterior
termination of the body.

The antennules, sometimes referred to as the first antennae, are the
first pair of cephalic appendages. They are long and tapering uniramous
structures, formed of the endopodite only. The strong broad bases are
inserted in the forehead somewhat below the level of the median eye and
very close together. The seven podomeres of each antennule taper to very

[4]

Fic. 1. Left valve of Cypridopsis vidua with the outer chitin and the calcareous
layers removed to show the organs in the epidermis.

muscles from rear sac to dorsal part of shell
duct from liver to stomach

rear soc

excretory gland B
(shell gland)

anterior posterior

end sac
ventral

scors of mandible
adjustor muscles

Fic. la. Labeled diagram of Fig. 1.

Fig. 2. Cypridopsis vidua with the left valve removed to show the appendages.

mandible

“Endbigel” of maxilla

branchial (exopodite) plate of maxilla
3rd thoracic leg

end claw

lateral lenses of the eye

frontal lens

exopodite plote of mandible
ontennule
ontenna

sense club

exopodite plate

seto with
bulbous bose

é maxilla middle masticatory process
moxillary palp

Fic. 2a. Labeled diagram of Fig. 2.

[6]

°O 100
aa

Fic. 3. Cypridopsis vidua cut along the median sagittal plane, and with the left
half removed.

stomach wall

food boll

digestive fluid

ventral wall of front stomach

eye

dorsal Wulst

excretory gland A (gland of antennule)
antennule

chitia framework of head

excretory glandC (gland of the maxilla)
gland N (gland of the first thoracic leg)
uterus

egg with nucleus

seminal receptacle

spiral canal

rear gut

sense club anus

pharynx muscle

—

glond L (tip gland

uterine opening
vaginal opening
genital lobe
chitin "stick"

Y-shaped process
mandible teeth
“roke-shaped organ"
porognath

maxilla

2nd thoracic leg
\st thoracic leg
subdermal cells
hypostome

Fic. 3a. Labeled diagram of Fig. 3.

8 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

small diameter at the distal end. The four distal podomeres are equipped
with very long, feathered setae which are used for swimming and for
balance. The two antennules curve forward and downward and diverge
somewhat at the ends. The long setae spread out forward in a horizontal
plane like two fans. When the animal is walking or climbing, these long
setae are constantly feeling the area in front of it.

The antennae, also known as the second antennae (when the antennules
are referred to as the first antennae), are the second pair of cephalic ap-
pendages. They are attached at the side of the forehead below the anten-
nules, very near the junction with the upper lip. The antennae are more
strongly constructed than the antennules and bear long claws at the end.
The five podomeres may be classed as two of the protopodite and three of
the endopodite. The exopodite is either absent entirely or represented by
a thin seta. The antennae are directed forward, then down, and distally
posterior and ventral. The first podomere of the endopodite bears two
essential features: the swimming or natatory setae and a sense organ. The
five long, feathered setae are attached to a scale on the distal inner mar-
gin, and extend beyond the terminal claws. The sensory organ is club-
shaped and suspended from the ventral posterior margin near the middle
of the podomere. In swimming, the ostracod uses the antennae and the
very flexible antennules simultaneously to row itself through the water.
The antennules are flexed upward and back, while the antennae are
forced downward and back.

The helmet-shaped upper lip hes immediately below the forehead and
forms the anterior ventral termination of the body. The rear ventral rim
of the upper lip is the forward edge of the mouth opening. There are no
appendages attached to the upper lip and it can be seen clearly in a side
view of the dissected animal.

From the chitinous framework of the upper lip there are two triangular
chitinous processes projecting into the mouth cavity.

The heavily toothed mandibles lie on either side of the mouth in inden-
tations between the upper lip and the hypostome. The first podomere of
the mandibles is elongate and lies almost vertical along the sides of the
body, its dorsal tip reaching nearly to the level of the antennules. About
one-third of the distance from the teeth toward the dorsal tip, a palp
projects anteriorly from the elongate podomere. This palp is strongly
developed and consists of a second podomere of the protopodite and
three additional podomeres representing the endopodite. From the second
podomere of the protopodite (basal member of the palp) a delicate, hand-
shaped branchial plate extends dorsally from a chitinous socket. This is
the exopodite. It terminates in long, tapering hairs. The endopodite has
many long setae extending downward and forward from the two proximal
podomeres, which curve downward. The third podomere is shortened and

Fic. 4. Right half of Cypridopsis vidua. Gland L, gland N, and the genital or-
gans have been removed to show the musculature.

stomachwall to ventral wall of front stomach
esophogus to ventral wall of front stomach

tissue supporting the stomach
excretory gland A to endoskeleton
esophagus to endoskeleton

chitinous center of closing muscles
excretory glandC fo endoskelefon
excretory gland C
to body wall

anterior extension of eye

ocross base of dorsal Wulst

circumesophogeal

forehead to
esophagus

uterine opening to
reor body wall

front to rear wall of

genital lobe
uterine opening fo

genital lobe

chitin "stick" to

upper lip to esophagus
upper lip to Y-shoped process

hypostome
to endoskeleton

esophagus to endoskeleton
hypostome to endoskeleton

genital lobe (vaginal)

uterine opening to
genital lobe
endoskeleton to closing muscles

Fic. 4a. Labeled diagram of Fig. 4.

[9]

marece ere ecer cers:
tees

(a

Fig. 5. Right half of Cypridopsis vidua. Forehead, upper lip, hypostome, diges-
tive system, and the genital organs have been removed.

dorsal area to endoskeleton .
ventra/rim of antenna to dorsal area

mandible to dorsal area

posterior rim of lst leg to endoskeleton
mandible to endoskeleton

dorsal area to
posterior body wall

dorsal rimof antenna to dorsal area

ventral rim of antennule to dorsal area
dorsal rim of antennule to dorsal area
dorsal rim of antennule to endoskeleton

ventral rim of antennule
fo endpeeleten dorsal rim of 2nd leg to

endoskeleton

antennule

mandible to

dorsal area posterior rim of

furca to body wall

dorsal rim of

antenna to endo. anterior rim of

furca to body wall
mandibular palp

ventral rim of 2nd leg

antenna to endoskeleton

ventral rim of antenna
to endoskeleton

mandible to endoskeleton

claw of 2nd leg

onterior rim of Ist leg
to endoskeleton

mondible posterior rim of maxilla

to endoskeleton

maxillary palp
anterior rim of maxilla to endoskeleton

Fig. 5a. Labeled diagram of Fig. 5. The muscles are labeled in slant lettering.

[10 J

TCESPCP PRL cer eres
7

Fic. 6. Right half of Cypridopsis vidua showing the nervous system.

ganglion of the antennule antennule and dorsal region
PROTOGEREBRUM optic nerve to lateral lenses antenna and frontal region
DEUTOCEREBRUM optic nerve to frontal lens small ganglion of mandible base
ganglion at base center of mandible base

of the antenna Ist leg and ceatral region

ganglion of 2nd

podomere of the antenna 2nd and 3rd legs and

immediate area
antennule nerve

antenna nerves

furca and :
posterior region

TRITOCEREBRUM

CIRCUMESOPHAGEAL
GANGLION

mandibular palp nerve
upper lipand mouth

furca nerve

L~ nerves of the
genital region

ganglion of mandibular palp

PERIBUCCAL RING
hypostome and mouth region

3rd leg nerves

2nd leg nerve

Ist leg ganglion }
mandible nerve VENTRAL CHAIN OF GANGLIA

; maxilla ganglion
moxillary polp nerve .
maxilla

Fic. 6a. Labeled diagram of Fig. 6. Sensory nerves are indicated by vertical
lettering, and the motor nerves are indicated by slant lettering.

[11]

12 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

armed with three strong claws at the end. The palp is used as a feeding
and feeling organ.

The hypostome is the ventral posterior portion of the head. It is a
keeled structure, shaped like the sternum of a bird. The forward end
widens to make the posterior portion of the mouth. The pointed posterior
end of the hypostome curves upward and terminates in a chitin girdle-
shaped loop. At the rear of the mouth is a pair of chitin shafts with
toothed structures on the ends. These are frequently ignored or mis-
interpreted in ostracod descriptions. They are called rechenformig or
rake-shaped organs by Claus, and that descriptive term will be used in
this paper. The rake-shaped organs are straining and feeding structures.

The fourth pair of cephalic appendages, the maxillae, lie behind the
mandibles and on the sides of the hypostome. The basal podomere is
strongly developed and ends distally in three short, cylindrical mastica-
tory processes, which are scarcely movable, and a palp of two podomeres
bearing fine claws and setae, which can move independently of the basal
member. The exopodite is especially well developed in the maxilla as a
branchial plate bearing numerous feathered setae on the posterior rim.
This plate is respiratory in function and in seventh and eighth molt
stages, where the calcium carbonate and coloring of the shell are not as
dense as in the adult, it can be clearly seen in the living animal continu-
ously sweeping forward and back on its basal pivot. The palp and three
distal masticatory processes lie more or less in a transverse plane, so that
a side view usually shows only the outermost member, the palp. The
maxilla slants forward and down in the animal, and in the lower portion
is strongly curved around the hypostome. This brings the masticatory
processes of the two maxillae to the median plane immediately posterior
to the teeth of the mandibles. Although the small processes themselves
have very little independent motion, the whole maxilla is in rapid motion
in the feeding processes, passing small particles toward the mouth.

It has been noted that the boundary between the head and thorax is
not sharply set off. This is particularly true in the Cypridae. The hypos-
tome at the posterior end slants upward and converges in a prow struc-
ture. At the dorsal posterior tip of this prow, a chitin girdle is formed of
processes which extend laterally on the sides and then recurve and join
to form a loop. From the outside tips of this girdle, the first thoracic
legs are suspended.

TuHoracic REGION

The first pair of thoracic legs is modified in the Cypridae for feeding.
It was their position and function which led early German workers to
refer to this pair of legs by other terms. Zenker called them the zweztes

Fic. 7. Right valve and mandible of Cypridopsis vidua. The closing muscles and
the mandible adjustor muscles are also shown.

“ "
teeth flange groove

selvage :
(pseudocardinal tooth)

selvage

flange
proximal limit

selvage
of grooved orea

selvage

flange groove

inner margin

anterior
protuberance

list

selvage

inner margin
flange

selvage

inner margin

line of concrescence

selvage

, closing muscles
list selvage

selvage |
line of concrescence

Fic. 7a. Labeled diagram of Fig. 7.

113]

14 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

Maxillenpaar (second pair of maxillae), and Claus referred to each of
them as a NKieferfuss (jaw-foot). However, a morphological comparison
with the Cytheridae, where the thoracic legs are all very similar, shows
these legs to be modified thoracic legs, and they are discussed here as
appendages of the thorax.

The leg is small, and because of its position behind and under the max-
illa, it is difficult to see in a side view. It has the shape of an inverted T;
the protopodite makes the stem and anterior half of the crossbar, and the
palp (endopodite) makes the posterior half. The distal end of the proto-
podite is provided with rather long setae which are used in feeding. This
portion of the leg normally lies almost horizontal, pointing toward the
mouth, and partially obscured by the masticatory processes of the max-
illa. The palp extends posterior and outward, and bears three long setae
on the distal end. There is also an exopodite, a delicate semicircular
branchial plate, which extends posteriorly from the vertical stem. This
bears five tapering hairs on the posterior rim which are transparent and
difficult to see in unstained material.

The second pair of thoracic legs is strongly developed for use in walk-
ing, climbing, and clinging to inclined surfaces. Each is composed of five
podomeres and terminates in a strong, curved claw. The basal podomere
of this uniramous appendage is often incompletely described in literature.
It hes almost vertical, behind the first thoracic leg and the hypostome. It
is covered by a strong, complex chitin framework, and is strongly
joined to the body on the dorsal and inner margins. The other four podo-
meres are directed backward horizontally. The first three are well de-
veloped, and the fourth is short and tapered, like a truncated cone. This
distal podomere is strongly attached to the strong claw, but has great
freedom of movement at its junction with the penultimate podomere. In
walking and clinging, the two strong claws of the second thoracic legs
act in a forward direction in opposition to the backward action of the
terminal claws of the antennae.

The third pair of thoracic legs is modified for cleaning the inside of the
shell. Each of the legs is directed downward, then backward, and then
dorsally, so that the shape is that of a modified U. The first podomere of
this uniramous appendage is the most flexible and complexly muscled
podomere of the whole animal. The chitin forming the cylindrical wall is
delicate and highly flexible, enabling the leg to turn a full 180° on itself.
Thus the range of the cleansing action of this appendage covers almost
the entire interior of the shell. Of the three other podomeres, the first two
are long and the terminal is very much shortened. The penultimate podo-
mere is notched inward at its distal end. Around the dorsal border of this
notch it bears a semicircular fringe of hairs. The ventral border of the
notch is modified as a small chitin plate. This plate is the ventral face of

GENERAL DESCRIPTION 15

a curious set of pincers at the end of the leg. The dorsal face of the pincers
is a projection of the ultimate podomere. In addition, the short ultimate
podomere also bears an elongate, toothed claw which can be used for
dislodging foreign, irritating materials from between the body and the
shell. The pincers are a very efficient organ, and can be observed to seize
small foreign particles and remove them from the shell.

The genital regions lie behind the third thoracic legs, on the ventral
surface of the thorax. They are seen externally as two lobes, elongate be-
tween the thoracic legs and the furcae. Near the middle of the lobes, on
the sides nearest the medial plane, are the paired vaginal openings, framed
with thick chitin. The paired uterine openings he behind and inside the
vaginal openings.

The fureae are much reduced in this species, and appear as short bases
with tapering “‘flage'la” at the distal ends.

DIGESTIVE SYSTEM AND GLANDS

The digestive system consists of the mouth, esophagus, stomach, intes-
tine, rear gut, and anus. The mouth is a large atrium with the distal ends
of the mandibles at the two sides, the upper lip at the front, and the hy-
postome at the rear. The esophagus is very muscular and leads upward
into the large stomach. The movement of food from the esophagus into
the stomach is aided by a large tongue-shaped organ at the front of the
stomach, called the dorsal wulst. The stomach is separated from the large
rear gut by a narrow, heavily muscled passageway, here termed the intes-
tine. Most of the digestion takes place in the stomach. The food is formed
into balls which pass from the stomach into the rear gut, and finally are
expelled as fecal pellets.

The livers he in the epidermal layers of the two valves and pour their
secretion into the anterior part of the stomach through two lateral ducts.
This secretion acts as a digestive fluid.

Excretion is accomplished by three pairs of glands, here called excre-
tory glands A, B, and C. The first pair is located on the sides of the
esophagus and empty below the antennules through ducts. The second
pair is located in the epidermis of the valves, opening between the valves
and the antennae by short ducts. The third pair is found near the middle
of the body, and empty behind the maxillae through S-shaped ducts.

There are also glands producing secretions, which are here called glands
L, N, and O. The first pair is located in the upper lip and pour their
secretion into the mouth. They appear to be salivary glands. The second
pair is found near the middle of the body, to the inside of the two excre-
tory C glands. Their secretion is emptied through the posterior borders
of the first thoracic legs. The third pair is found in the genital lobes, and
connect to the vaginal atria. They may be vestigial copulatory glands.

III. Detailed Description

ANTENNULES

The long, tapering antennules are very important organs to the ostra-
cod, serving as swimming and feeling structures. In swimming, the ani-
mal propels itself forward by strokes of the antennules and antennae.

In walking and climbing, the setae of the antennules are spread out
in front of the animal, their tips lying in a horizontal plane. They are
constantly in motion, exploring the area ahead. If one of the antennules
be damaged, the motion of the animal in walking becomes erratic, al-
though the appendages used for walking are not impaired at all. This
strongly substantiates the writer’s theory that the antennules serve as
balancing organs.

When the animal closes the shell, the antennules are strongly curved
downward by contraction of the flexor muscles. The long natatory setae
are then directed backward between the antennae and along the ventral
margin inside the shell.

In addition to the remarkable flexibility of these appendages, there is
another motion which has been observed. The animal is able to shorten
the length of the antennules by as much as 10 by simultaneous contrac-
tion of the flexor and extensor muscles. It is not known what use the ani-
mal makes of this ability. When an ostracod was placed in a chlorotone
solution, it slowly shortened and lengthened the antennules several times
before completely relaxing under the influence of the narcotic.

The two antennules are joined to the forehead at a position in the an-
terior one-third of the animal about 40 below the dorsal border. The
basal podomeres are set very close together; the forehead narrows to
25y between them.

The basal podomere of each antennule has a large triangular opening
on the inner face (Fig. 8). The podomere is not joined to the forehead
directly along the entire perimeter of this opening. The outer border is
attached directly, but the inner borders have a triangular inset of flex-
ible chitin. This inset is joined to the basal podomere along the two distal
sides, and to the forehead along the proximal side (Fig. 14). In a needle
dissection, the inset frequently remains attached to the forehead.

There are two structures which give strength to the attachment of
antennule and forehead. The first is a chitin rod with a forked end which
lies embedded in the surface of the forehead (Fig. 13, delta). The short
fork at the end is directed anteriorly, and fits into a small notch on the

[ 16 ]

DETAILED DESCRIPTION dt

_ Ist (basal) podomere

Fa :
4 \ ‘
/ : ia
Detail of the \

"feathering of the
natotory setae with
secondary setae. Same
scale as complete drawing.

" 7
sensory organ

5th podomere-~_

6th podomere~~

a
7th (terminal) podomere
_-natatory setoe

#
natatory setae

0 100u

fe shoei |

Fic. 8. Inner face of left antennule.

outside proximal border of the basal podomere. The second structure is
another chitin rod which fits against the base of the triangular inset. This
rod lies horizontal (Fig. 14, alpha) and its posterior end meets with an-
other rod (Fig. 14, beta) which terminates anteriorly at the base of the
antenna. These two rods, which together link the inset of the antennule to
the base of the antenna, have no free motion; therefore, they must be
considered as strengthening and supporting structures rather than as
mechanisms for transmitting motions between antennule and antenna.

The length of each antennule is approximately 230, and the natatory
setae extend an additional 220u. The antennule is composed of seven
podomeres, of which the proximal two probably represent the protopo-
dite and the distal five the endopodite. (Claus 1893, p. 22: “Von diesem
besitzt das basale den bei weitem gréssten Umfang und ist mit dem kur-
zen und betrachtlich verschmélerten zweiten Gliede als Stamm oder

18 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

Schaft der Gledmasse zu betrachten.’”’) There is no development of the
exopodite, unless it be the short seta on the dorsal distal border of the
second podomere.

The basal podomere is by far the largest. It measures 100» in length,
and tapers from a height of 70m at its proximal end to slightly over 30u
at its distal. The large opening and the junction with the forehead have
already been described. There are three well-developed setae on this po-
domere, all with large bases. The first is about 50» long, attached on the
dorsal border. The second and third are attached closely together near
the ventral distal end; the proximal seta is over 100» long, and the distal
about 80u.

The second podomere of the antennule is short, but strongly chitinized
(Plate 54, No. 254). It is about 30» long, and tapers from 30 to 25y in
diameter. There is only one seta, about 30u long, attached to the dorsal
distal end. This small seta may represent the vestige of the exopodite.

There is also a very delicate sensory structure located on the outside
face near the ventral border. It is only 10p long, and consists of a narrow
tubular shaft directed forward and a short, flared, bell-shaped end. This
structure has been described by Rome (1947, p. 90), who termed it
Vorgane chemocepteur. Its definite use is unknown.

The third and fourth podomeres are partially fused. Although the
junction between them is well defined, there is no movement possible.
They appear to act as a single unit in all motions of the antennule. The
third podomere is 30 long and 20u in diameter. It bears two setae near
its distal end; both are attached on the outer side, the dorsal one about
60u long and the ventral one about 25. The fourth podomere fits against
the third with no constriction at the fused junction. It is 20u long and 20u
in diameter. There are four distal setae; the ventral one is only 25, long,
but the three dorsal are well developed and serve as natatory setae. Two
of these are 220» long, and the other is 150z.

The distal one-half of all the natatory setae are “feathered” with very
delicate secondary setae (Fig. 8). These small secondary setae are
seen with difficulty in water; and when the antennules are embedded in
balsam or diaphane, the indices of refraction of the chitin and the mount-
ing medium are so close that the secondary setae become invisible. The
secondaries are spaced approximately every 10 in the “feathered”’ por-
tion, with each dorsal seta paired with a corresponding ventral one. Each
one is about 20» long.

The fifth podomere is 204 long and 15p in diameter. At its distal end
it bears dorsally two natatory setae 230» long, and ventrally one seta 20
long.

The sixth podomere is 20u long and 10, in diameter. Distally it bears

DETAILED DESCRIPTION 19

three natatory setae on the inner dorsal side. These are the longest of al!
the setae, measuring 250».

The terminal podomere is 25h long and 5y in diameter. The distal end
is enlarged somewhat, and the three setae are joined to the end. Two of
these are 220u long, and the third is about 80uy.

The basal podomere is capable of movement itself. Muscles connect the
outer proximal rim to the dorsal region of the shell and to the endoskele-
ton. The dorsal edge of the base of the antenna has one extensor to the
dorsal region of the shell and a second extensor to the endoskeleton
(Fig. 5). The ventral edge has one flexor to the dorsal region and another
to the endoskeleton. (Plate 1, Nos. 1938, 194; Plate 33, No. 201).

Several muscles extend from the proximal rim of the basal podomere
to the dorsal proximal tip of the third podomere. These strong extensors
are used in the powerful swimming stroke. There is a small muscle con-
necting the ventral proximal tips of the first and third podomeres, serv-
ing as a flexor. The movement between the basal and second podomere
is not independent of the rest of the antennule, and is somewhat restricted.

Additional extensor muscles connect the distal ends of the third and
fifth, and of the fifth and terminal podomeres. There are corresponding
flexor muscles in the ventral positions (Fig. 8).

The nerve system of the antennule is connected with the central por-
tion of the cerebrum known as the deutocerebrum. The nerve bundle leads
to the spherical ganglion in the basal podomere of the antennule (Plate
62, No. 284). This ganglion is well developed. There is a large nerve
bundle from the dorsal part of this ganglion, which tapers to a small di-
ameter at the end of the protopodite (Plate 9, No. 45; Plate 10, No. 49;
Plate 30, No. 188). The nerve cord extends through the antennule to the
terminal end. The small motor nerves operating the muscles of the anten-
nule also originate in the deutocerebrum.

The ganglia of the two antennules may be the centers of the sense of
balance. This is suggested by the erratic movement of the ostracod in
walking, after one antennule is amputated. The small size of Cypridopsis
vidua prevents the severing of the sensory nerves between the ganglia and
the deutocerebrum without damaging the structure of the head and an-
tennules and killing the ostracod. Therefore, the writer’s interpretation
of the antennule ganglion as a “balance center” is incompletely substan-
tiated.

ANTENNAE

The two antennae are essential locomotor appendages of the ostracod.
They are used in conjunction with the antennules for swimming, and
with the second thoracic legs for walking and climbing. Many early

20 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

2nd podomere of protopodite
\
\ Ist podomere of protopodite

long seta (which
may be vestigial
exopodite)

NN

“sense club”

\ ~ Ist podomere of endopodite

-7end claws of terminal
ae, podomere

‘ : 4
notatory setoe--~ \ SS
‘ ‘

~~

“end claws of

2nd podomere of
endopodite

ie) 1004

a eee a a

Fic. 9. Inner face of right antenna.

writers regarded the antennae as the first pair of feet (Hoeven 1856, p.
633). Because of their close coordination with the antennules in swim-
ming, other workers on ostracods, including Claus (1893, p. 24), desig-
nated the antennules as the “first antennae” and the antennae as the
“second antennae.”

The motion of the antennae in swimming is downward and back. The
long natatory setae provide sufficient surface for powerful propulsion.
The end claws are used in walking, climbing, and clinging to inclined
surfaces. The antennae can be bent to a position close to the forehead and
upper lip, and are entirely encased within the shell when it is fully closed.

The antennae are joined to the forehead near its junction with the
upper lip (Fig. 14). They are set onto the sides of the head with the
bases 80u apart (Plate 4, No. 15). A chitin rod, lying embedded in the
wall of the head (Fig. 13, beta), fits into a small cavity in the chitin rim

DETAILED DESCRIPTION 21

2nd podomere of protopodite
/

basal podomere
!

long seta (exopodite)

“sense club"-~_

ie) 1004

Fic. 10. Outer face of right antenna.

of the basal podomere of each antenna. Posteriorly, this rod joins an-
other rod connected to the antennule (Fig. 9). Neither of the two rods is
capable of movement, and they only strengthen the wall of the head
structurally to withstand the strong reaction from the powerful anten-
nae and antennules.

The total length of the antenna is 360u, and the end claws extend an
additional 80u. The natatory setae extend slightly beyond the distal
ends of the claws. The five podomeres of this uniramous appendage may
be divided logically into two of the protopodite and three of the endo-
podite (Fig. 9). The exopodite is absent, or reduced to a long, narrow
seta.

The basal podomere is powerfully reinforced by a chitin framework. It
is shaped very much like an elbow joint used in plumbing — one opening
fits against the head, and the other joins onto the second podomere. This
basal member of the protopodite is practically incapable of movement,
being lightly fused to the head. It is 60» long and 80» high at the anterior
rim.

The second podomere of the protopodite is slightly over 100 long. The
cross-section of this podomere is elliptical, and it is about 60 high and
45p thick. The chitin framework differs from that of any other podomere
of the body, and controls the movement of the podomere to a great degree.
At the proximal end, the ventral perimeter is reinforced by a U-shaped
chitin structure. The two tips of this structure lie on the sides of the podo-
mere (Figs. 4 and 5) and act as fulera to control mechanically dorsal and
ventral movement of the antenna. The remainder of the proximal rim is
connected to the basal podomere by thin, highly flexible chitin. Distally
from the U-shaped piece, chitin rods extend along the sides to a dorsal

22 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

reinforcement at the distal end of the podomere. There are two setae near
the distal end. The ventral one is a delicate seta 120 long attached to
the inside. The dorsal seta measures 150” long; it may be the vestige of
the exopodite.

The first podomere of the endopodite is 120» long. It is also elliptical
in cross-section, measuring 45 high and 35, thick. At the proximal end
there is a broad notch of strong chitin on the dorsal side, which fits around
the chitin prominence on the end of the second podomere. There are two
curious sensory structures on this podomere, both of them on the ventral
border. The first, an unusual club-shaped appendage, is 30» from the
proximal rim; the second, a seta with a large, swollen base, is at the distal
tip. The club-shaped structure has a shaft 10 long and about 3y in dia-
meter, and an enlarged tip of the same length and about 5» in diameter.
It has been called the ‘sense club” by Sharpe (1918, p. 798), and Spir-
borsten oder Spiirfaiden by Claus (1898, p. 26), who originally described
it. Claus believed it to be sensitive to chemical and physical changes in
the water. Hoff (1942a, p. 48), states that it has been considered an ol-
factory organ. The shaft of the club contains nerve fibers, so it would
appear that the structure is sensory. However, the specific use or the
specific sensitivity of the organ has never been proved. The terminal seta
with the enlarged base may also be sensory. It would be a very exacting
project to prove the particular sensitivity of these two structures. About
30u from the distal end of the podomere, a chitin scale is attached to the
inside dorsal edge. To this scale the natatory setae are attached like the
teeth of a comb. Five of these setae are about 200» long, and the sixth is
only a little over 50u. All of them are “feathered” with secondary setae
in the distal one-half of their length. The longest project slightly beyond
the ends of the terminal claws.

The second podomere of the endopodite is dorsally about 60, long, but
ventrally it is only 40u. The terminal podomere is set into this ventral
indentation. Near the middle of the inner side there is a small ventral
comb structure bearing four setae slightly less than 100u long. At the
dorsal termination there are two long claws bearing teeth. The claws are
90u long. The dorsal one of the two is heavier and equipped with longer,
stronger teeth than the ventral (Fig. 9).

The terminal podomere is very small. The length is only 20, and the
diameter 10u. It extends less than 10 beyond the dorsal tip of the second
podomere of the endopodite, since it is set into a ventral niche. Distally
this ultimate podomere terminates at the bases of two claws. The dorsal
claw is over 80m, and the ventral one is less than 60» long. Both bear small
teeth in their distal portions, those of the dorsal claw being very fine.
(Plate 56, Fig. 263).

The musculature of the antenna is marked by the unusual develop-

DETAILED DESCRIPTION 23

ment of the flexor muscles. These are more numerous and much larger
than the extensors. This is entirely in accord with the observed movement
of the antenna in swimming and walking.

Although the basal podomere is joined directly to the side of the fore-
head and is capable of only limited movement, it has extensor and flexor
muscles attached to the outer rim connecting it both to the dorsal region
of the shell and to the endoskeleton (Plate 2, No. 5). A group of three
small flexors extends from the dorsal rim to the median dorsal region
(Plate 28, No. 181; Plate 31, Nos. 193-95). One small extensor connects
the outer ventral rim with the dorsal region. The muscles to the dorsal
region do not move the basal podomere to a great extent, and they may
serve to raise the anterior portion of the body by their contraction. The
muscles to the endoskeleton consist of one flexor attached to the dorsal
rim and one extensor attached to the ventral (Plate 9, No. 46; Plate 33,
No. 203).

The second podomere is lowered by three large flexor muscles which
extend from its proximal ventral tip to the outer proximal rim of the
basal podomere. It is raised by a single small extensor which is attached
at the distal ventral tip and terminates posteriorly at the rim of the basal
podomere. It has been pointed out above that the tips of the proximal U-
shaped chitin structure act as fulera. Movement of the podomere hinges
on these two lateral points.

The third podomere (first podomere of the endopodite) joins the second
at almost a right angle. The muscles which operate this podomere are
modified from the usual arrangement by this factor. The extensor muscle
is attached at the middle of the dorsal border, connecting it with the distal
dorsal tip of the second podomere. The three flexor muscles are attached
in the normal manner, linking the proximal ventral rim of the third po-
domere back to the corresponding position of the second.

The second podomere of the endopodite is operated by an extensor
of the usual arrangement. There are, however, two flexors. The first flexor
connects back to the proximal dorsal rim of the first podomere of the
endopodite. The second flexor extends all the way back to the distal dor-
sal area of the second podomere of the protopodite.

The terminal podomere possesses independent movement. It has small
extensor and flexor muscles connecting back to the proximal rim of the
preceding podomere in the usual manner.

The end claws do not appear to possess independent action, but move
only with their corresponding podomere.

The nervous system of the antenna is not complex, but it 1s incom-
pletely described in literature. The sensory bundle of nerves leads to the
portion of the cerebrum which has been designated the ‘“tritocerebrum.”
The antenna itself houses two ganglia, one in the basal podomere (Plate

24 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

dorsal apex

ie) 100%

exopodite plate
2nd podomere of es
the protopodite : : ep eX.

“ tae 9

Ist podomere of endopodite

2nd podomere
of endopodite

-

3rd podomere
of endopodite

=
end clows

Fia. 11. Inner face of right mandible.

69, No. 303) and one in the second podomere (Plate 9, No. 46; Plate 31,
No. 195). The proximal ganglion is small and globular, about 10, in di-
ameter. It is connected to the tritocerebrum by a small nerve bundle about
10u long. There are two nerve bundles connecting the two ganglia, the
dorsal one being the larger. The distal ganglion is laterally much com-
pressed, and somewhat triangular in side view. One dorsal and one ven-
tral nerve bundle extend distally to the end of the antenna, with side
branches to the sense club, various setae, and the bases of the claws. The
motor nerves operating the muscles of the antenna also originate in the
tritocerebrum. They are difficult to trace in Cypridopsis vidua, but in
larger species, such as Candona crogmaniana, they are much more distinct.

MANDIBLES

The mandibles are the only true masticatory appendages of the ostra-
cod. They he at the sides of the atrium, and the distal teeth can meet in
the center. They retain the full character of crustacean appendages, hav-
ing both endopodite and exopodite parts in addition to the protopodite.
The endopodite is developed as a palp, and the exopodite is a plate bear-
ing setae. The palp functions as an accessory feeding organ, passing par-
ticles of food backward to the mouth.

DETAILED DESCRIPTION 25

Lexopodite plate

pea 2nd podomere of protopodite

/
Ist podomere of endopodite
/

-2nd podomere of
—\. endopodite

:
SS < 3rd podomere of

ce, KN endopodite

\ \
4
pny ay,

basal podomere

\

ee

a

teeth----
Fig. 12. Outer face of right mandible.

The basal podomere is the largest of all podomeres of the ostracod, and
is heavily chitinized. It is 300u long and over 60» wide near the center.
It joins onto the body wall around the subcuneate inner flange, which is
over 200» long. The distal 60, of this podomere is set off by a shght con-
striction, and bears the seven rows of teeth (Fig. 11). The rows of teeth
are best developed at the distal end, and become shorter and less dis-
tinct proximally (Plate 57, No. 269; Plate 60, No. 280). The five distal
rows are composed of three teeth each, but the proximal two are fused
into roughened bars. There are also some very short sensory setae inter-
spersed through the toothed area. The basal podomere has only one large
seta, about 35p long, attached to the anterior edge in the distal portion
(Fig. 11).

The dorsal apex is joined to two chitin rods which are operated by
muscles extending to the side of the shell, just anterior to the closing mus-
cles (Fig. 7). These muscles do not penetrate the body wall, but extend
through soft tissues (Plate 15, Nos. 88, 89; Plate 35, Nos. 210, 211). They
apparently adjust the angle of the basal podomere of the mandible. Scars
of these muscles are often misinterpreted as those of additional closing
muscles.

The second podomere of the protopodite is attached at the side of the

26 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

basal podomere and about 200 from the dorsal tip (Fig. 12). It pro-
jects anteriorly, and forms the basal unit of the palp. It is 654 long and
subelliptical in cross-section; the height tapers from 60 to 30u, and the
width from 30 to 25u. There is a shallow cup on the outer dorsal side
into which the base of the exopodite plate is set (Fig. 12). Near the distal
end of the podomere are two ventral, strong-toothed setae 90 long. It is
not known what special use is made of these unusually well-developed
setae.

The exopodite plate is a very delicate structure, and can only be seen
clearly in a stained specimen. It is about 50 long and bears seven setae.
These setae are shrunken to small diameter in a diaphane-mounted dis-
section (Plate 58, No. 271), but in a freshly dissected animal, they are
seen to have expanded bulbous bases and “feathered” edges. The six
terminal setae are 100u long, but the one attached at the mid-point of
the anterior edge is only about one-half that length (Plate 56, No. 264).

The first podomere of the endopodite is only 20” long and 30, in dia-
meter. Distally it has two dorsal and four ventral setae. The dorsal setae
are of unequal length, the longer measuring 130 and the shorter only
60. The ventral four setae, varying from 50 to 70p in length, are attached
to a scale to form a comb-like structure, very similar to that of the nata-
tory setae on the antenna.

The second podomere of the endopodite is 45 long and 25 in diameter.
All of the setae are on the distal portion. On the inner face there are two
comb-like structures, the dorsal one having three setae 60 long and
the ventral one having four setae 100u long. These latter extend beyond
the terminal claws. In addition, there are three isolated setae: one at the
dorsal apex 50 long, a second on the inner face about 30 long, and a
third on the ventral border only 20» long.

The third podomere of the endopodite terminates the palp. It is only
15 long and 15» in diameter. At the distal end it bears three claws, all
equally developed and about 60, in length. These claws are almost con-
stantly in use to pass food backward to the mouth.

The basal podomere is connected by muscles both to the dorsal part of
the shell (Plate 31, Nos. 192, 193) and to the endoskeleton (Plate 5, Nos.
17, 18). Two small muscles extend dorsally from each mandible, and four
large and at least three small muscles connect it to the endoskeleton.
These latter are arranged in a complicated pattern, making it difficult to
discern the exact number, even in 10m sections. They cross one another
(Plate 5, No. 19), permitting the adjustment of the mandible to many
positions. Their primary purpose is to pull the teeth together in the atrium
in the chewing process, and they may all be called adductors until their
individual functions are understood in greater detail. The two muscles
to the dorsal part of the shell act as retractors, and also perhaps as diduc-

DETAILED DESCRIPTION 2t

tors. The muscles from the center of the shell valve to the chitin processes
attached to the dorsal tip of the mandible (Fig. 7) serve as diductors and
adjustors.

The second podomere of the protopodite does not appear to have mus-
cles for independent movement.

The first podomere of the endopodite has one extensor and three flexors
connecting its proximal rim to the posterior rim of the basal podomere
(Fig. 11).

There is apparently only one other muscle in the palp. This is a flexor
extending from the base of the terminal podomere back to the dorsal
proximal edge of the first podomere of the endopodite. Extension of the
podomeres of the endopodite must be accomplished by elasticity of the
joints, returning the podomeres to a fixed position when the flexor muscle
relaxes.

The nerves of the mandible are connected to the ventral chain of gang-
lia. The sensory nerve cord connects to a small ganglion in the basal po-
domere (Plate 31, No. 195). From this ganglion one branch extends down
into the distal end to the teeth and the accompanying small sensory setae,
and a second branch goes into the second podomere to a second small
ganglion. From this ganglion in the base of the palp, a small nerve bundle
extends to the end of the palp (Fig. 6).

The “mandible gland,” which hes in the distal portion of the basal po-
domere, is discussed under “Gland M.”

FOREHEAD AND Upper Lip

The whole front of the body of the ostracod is bounded by a blunt, re-
inforced chitin case constituting the forehead and upper lip. These two
divisions are not separated, but are fused together into one unit (Fig. 13).
This unit, like other sections of the body wall, is made up of two distinet
types of chitin. There is a distinct framework of strong chitin rods. The
spaces bounded by this rigid framework are filled by thin flexible chitin
which is fused to it — like the glass panes in a leaded window. The whole
encases the soft tissues within.

Each side of the forehead has a strong chitin process on the surface
which terminates anteriorly in a curved fork (Fig. 13, delta). These fit
against the outer rims of the antennules, as has been described. There are
also two chitin rods on each side which do not lie on the surface (Fig. 13,
alpha and beta). These rods are connected posteriorly. The anterior end
of the dorsal rod is set against the triangular inset in the base of the
antennule, and the anterior end of the ventral rod is set into a small
socket in the outer rim of the base of the antenna (Fig. 14). The bound-
ary of the forehead and upper lip is marked by a horizontal U-shaped
chitin rod around the anterior end of the body (Fig. 13, gamma).

28 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

chitin rod @

\~ forehead

\

‘/ “upper lip

x
"Y-shoped process”

hypostome

’
"rake-shaped organs”

Fic. 18. Chitin framework of the forehead, upper lip, and hypostome as seen
from the right side.

The upper lip has been appropriately described by Claus (1893, p. 28)
as a helmformiger Aufsatz (helmet-shaped structure). The anterior end
is bluntly rounded (Fig. 15), and the sides are subparallel. The ventral
surface is further reinforced by a number of elliptical chitin rods, which
are concentric anteriorly and converge posteriorly.

The posterior part of the upper lip forms the forward boundary of the
atrium, or mouth opening. This portion of the mouth has a chitin lining
equipped with numerous hairs directed inwardly and dorsally. The lining
has a slight groove along the median plane, and is strengthened by a
vertical chitin process (Fig. 16). This structure was referred to by Claus
(1893, p. 30) as Epipharyngealleisten (epipharyngeal rods). The writer
feels that this designation is misleading, and proposes the descriptive term
“Y-shaped process” in its place. The narrow spoon-like base of the “Y”
is ventral, and attached to the chitin lining; the arms of the structure are
directed dorsally and anteriorly (Fig. 15). The tips of the arms have
short hook-like projections pointing anteriorly, lying along the sides of
the esophagus (Fig. 13). The Y-shaped process is operated by a group
of muscles connecting it to the anterior portion of the upper lip (Fig. 4).

The posterior ventral rim of the upper hp has a notched border (Fig.
13). The roughened rim is not regularly notched, so that it cannot be

DETAILED DESCR PTION 29

° 100z
antennule

_
antenna

mondible

~~~upper lip

Fic. 14. Chitin framework of the forehead and upper lip are shown in solid
black. The bases of the antennule, antenna, and mandible are shown in their re-
spective positions.

said to be toothed. The upper lip has very little independent motion, and
the rasping is done primarily by the mandibles, abetted by the rake-
shaped organs.

The horizontal U-shaped chitin rod marking the boundary of fore-
head and upper lip is joined on its posterior ends by vertical chitin rods
(Fig. 13, zeta). These lie along the sides of the esophagus. At the ventral
end, these rods terminate in narrow triangular chitin processes pointing
inward at the back of the mouth but failing to meet in the median plane.

Posteriorly the upper lip is slightly indented at the sides to aecommo-
date the large basal podomeres of the mandibles, which bear the true
masticatory teeth on their ends (Fig. 14). The indentation allows the
teeth to meet in the center of the atrium.

HyPostoME

The hypostome or lower lip is located posterior to the atrium. It
forms a median sternum-like structure on the ventral side of the body.

30 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

re) ~--"Y-shaped process”
m\---'rake-shaped organ”
f----- hypostome
100u A
YS
chitin loop

Fic. 15. Hypostome and upper lip as seen from below and slightly to the front.

50u

Fig. 16 Fig. 17

Fic. 16. Front part of the mouth as seen from above and to the rear. Fic. 17.
Hypostome as seen from below. The rake-shaped organs are shown in place.

It is about 110» long and 100u wide at the front. The maxillae lie along
the sides, and the first thoracic legs are attached to the posterior tips.

The hypostome is shaped like the breast of a bird, with the posterior-
anterior positions reversed. It may also be described as similar to the
rear one-half of a fishing dory. The flattened bottom of this structure
has an A-shaped chitin framework, with the apex posterior (Fig. 17).
The dorsal framework is V-shaped. Dorsal and ventral portions are
joined together anteriorly by two slanting chitin rods (Fig. 13), and

DETAILED DESCRIPTION 31

posteriorly by two vertical rods set very close together and converging
toward the posterior point of the base.

The posterior stern is somewhat upturned, and at its dorsal termina-
tion is joined by a chitin girdle-shaped structure with elongate loops ex-
tending laterally. These loops are each 40u long (Fig. 15). The first thor-
acic legs are suspended from the outer tips of these loops (Fig. 20).

The broad anterior of the hypostome is the rear lining of the atrium.
There are two soft lobes at each side called the paragnaths (Fig. 3).
These are covered with hairs which are directed toward the well-defined
median groove (Fig. 17).

Two small masticatory appendages are embedded in the tissue of the
hypostome at the rear of the atrium. Each of these rake-shaped organs
has a vertical shaft 20» long, joined ventrally to the center of a horizontal
bar of equal length bearing nine teeth. The three teeth nearest the median
plane are somewhat fused at their bases. Long, inwardly directed hairs
line the outer edges of the shafts of these embedded rake-shaped organs
(Plate 85, No. 372). These hairs form a curtain across the back of the
atrium, and they may be used in straining certain food particles, although
this has not been established.

At the atrium, the ventral part of the hypostome is narrower than the
dorsal. This ventral indentation matches that of the upper lip, and to-
gether they form wide lateral V-shaped notches. In these notches the
mandibles fit closely when they are chewing. The sides of the hypostome
are also incurved somewhat to accommodate the maxillae.

The chitin of the body wall above the hypostome is flexible, permitting
movement of the hypostome by the muscles which connect it to the endo-
skeleton. There are three pairs of these muscles (Fig. 4). The first is
attached where the rake-shaped organs are imbedded; the second at the
dorsal anterior part, and the third pair near the center of the dorsal
chitin rods. The movement of the hypostome and the attached rake-
shaped organs is forward and back. Resemblance of this action to that
of a mammalian lower Jaw is marred only by the horizontal (rather than
vertical) orientation.

Both sensory and motor nerves of the hypostome are connected to the
ventral chain of ganglia (Fig. 6).

MAXILLAE

The maxillae are greatly modified appendages. The basal podomeres
partially surround the middle portion of the hypostome, and point for-
ward toward the atrium (Plate 57, No. 270). The terminal “masticatory”
processes are aligned laterally (Fig. 19), and serve only to pass food
particles toward the mouth. The maxillae serve a second function, that
of respiration. The large branchial plate is in constant motion, stirring the

32 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

— branchial plate

te} 1004

outer “masticatory”
~ process

basal podomere~— _-polp

inner “masticatory” process~

middle "masticatory" process~~ Zh

Fig. 18. Right mawxilla as seen from the outer side and slightly to the rear.

water inside the shell to speed up the absorption of oxygen by the body
wall.

The basal podomere curves inward at the top and terminates in
a forked process which Claus (1893, p. 37) termed the Endbiigel
(Fig. 19). The motion of the whole maxilla is controlled by this dorsal
process, which acts as.a fulcral point. There is no correct description of
the arrangement of this fulerum in literature. First, it must be pointed out
that above the hinge point of the first thoracic leg and the chitin loop
of the hypostome, there is a long chitin structure (Fig. 20). This struc-
ture has two median flanges which diverge toward the anterior end to
form a groove. The dorsal chitin process of the maxilla narrows to a

DETAILED DESCRIPTION 33

branchial plate
% XN
(exopodite) ~ \
~N

dorsal process ("Endbigel") /”

basal
podomere——

a
@ 0 100u

Fic. 19. Outer face of left maxilla.

curved rod immediately below the terminal fork. This curved portion
fits into the groove of the chitin structure over the first thoracic leg (Fig.
2; Plate 59, No. 274; Plate 60, No. 276). The terminal fork, which is
directed forward, prevents the maxilla from slipping downward through
the groove.

The curved basal podomere is about 180u long (Plate 57, No. 268),
although when seen from the side it usually appears shorter. The dorsal
part has already been described above. The ventral part has an inside cup
fitting close against the side of the hypostome. From this cup the three
“masticatory” processes and the palp project downward.

The problem of what portion of this appendage represents the endo-
podite is not simple. The middle and outer “masticatory” processes and
the palp are set off from the basal portion by definite sutures (Fig. 18).
This observation was also made by Claus (1893, p. 36), who coneluded
that the middle process was the first podomere of the endopodite, the
outer process was the second, and the palp represented the third and

34 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

fourth podomeres of this highly modified endopodite. This is a logical
analysis, for these members are definitely set off from the basal podomere.

This leaves the inner “masticatory” process as the only one of the
basal podomere. This process is 40 long and about 15 in diameter. The
distal end is blunt and bears seventeen setae. Only seven of these are
well developed, about 20u long; some are very insignificant and can only
be seen from below, since otherwise they are hidden by the larger setae.

The outer side of the basal podomere has a chitin-rimmed socket to
which the large branchial plate is attached. This plate is modified exo-
podite. The plate itself is 180» long and 50u wide near the middle. It
lies nearly horizontal. The ventral rim is fringed with twenty-five well-
developed setae. These vary from 70 to 120 in length. The proximal
five setae point down; the others are directed posteriorly, and between
their bases are reinforced by short chitin elements (Plate 56, No. 266).
The setae are feathered by very delicate secondary seta, which become
invisible in balsam or diaphane mounts.

The orientation of the entire maxilla is frequently misunderstood, and
it has been illustrated in many incorrect ways. The dorsal process of
the maxilla must lie above the first thoracic leg, as described above. From
this point of the maxilla curves outward and forward to the socket where
the branchial plate is attached. Then the maxilla continues forward and
down and flares inward to form the inner cup, to which the “masticatory”
processes and the palp are attached. The inner process is a direct con-
tinuation of the basal podomere. The processes and the palp are normally
arranged in an almost horizontal plane, with the setae pointing forward.
The inner processes of the left and right maxillae lie adjacent near the
median plane (Plate 74, No. 324).

The position of the branchial plate must be studied in its relation to
the rest of the body of the ostracod. We must note that the closing mus-
cles of the shell extend all the way through the soft inner body tissues,
and do not penetrate through the body wall or the chitin lining of the
hypodermis of the shell. Therefore, the body wall joins the chitin lining
of the hypodermis below the closing muscles. (Plates 3 and 4). This
forms the dorsal boundary of the open space inside the shell, to which the
free-moving branchial plate is limited by necessity. It is obviously im-
possible for the branchial plate to occupy a vertical position, for then it
would be cutting through the closing muscles themselves. Whenever the
branchial plate is shown out of its normal position so that other structures
can be shown, this should be explained in the text. Normally the branchial
plate lies almost horizontal, along the side of the shell (Plate 35, No.
210), and covers the third thoracic leg (Plate 24, Nos. 152-154).

The middle “masticatory” process, the first podomere of the endopo-
dite, is 40u long and about 15, in diameter. It is blunt at the distal end,

DETAILED DESCRIPTION 35

and has nine setae, only six of which reach significant length. The long-
est is nearly 40, long.

The outer “masticatory” process is nearly 50 long and slightly less
than 20» in diameter. Because of the variety of claws and setae attached
to it, this podomere has been termed the masticatory process, and is said
to be of taxonomic significance. One strong seta 25 long is attached on
the outer border, a few microns from the end. This is followed in order by
two long narrow setae, two claws, and one tapering seta, all of them
terminal. The claws of this podomere are significant in the separation of
many of the Cypridae. They are relatively simple in the case of Cypri-
dopsis vidua. They are about 40 long, tapering, and with a long groove
along the inner face. The sides of the claws flare slightly near the middle
and again near the end, but they are not notched, as are many others
of the Cypridae.

The palp contains two podomeres, representing the third and fourth
podomeres of the endopodite. It les outside the “‘masticatory” processes.
The proximal podomere of the palp is shghtly over 50u long and 20» in
diameter. One seta 40u long is attached on the outer edge of this podo-
mere 10u from the distal end. Nearer the end is a comb-like structure
with four setae 40u long. These are evidently sensory. The distal podo-
mere of the palp is quite small, less than 25u long and only 10» in dia-
meter. It is armed with terminal setae and claws. There are two strong
outer claws and one inner claw 30p long, and three small setae set in the
center.

The musculature of the maxilla is complex. Most of the action used
to pass food toward the mouth is imparted to the entire appendage by
muscles from the endoskeleton. These muscles are attached to the anterior
and posterior edges of the cup-shaped opening (Fig. 5). It must be re-
membered that the maxilla swings from the dorsal process, which acts
as a fuleral point. Therefore, the terms “flexor” and ‘‘extensor” are not
applicable to these muscles from the endoskeleton.

The palp is operated by one flexor and one extensor muscle attached to
the inside of the basal podomere. In addition, the second podomere of
the palp also has independent action; it has one flexor and two extensor
muscles. The flexor muscle extends back to the outer proximal edge of the
first podomere. The two extensors also connect to the outer edge of the
first podomere, one to the middle and one to the proximal tip.

The middle and outer “masticatory” processes have muscles connect-
ing them to the basal podomere, but their independent movement is
very limited. The inner ‘‘masticatory” process, a part of the basal podo-
mere, has no muscles at all.

The large branchial plate is operated by four muscles, so arranged
that the plate can be waved from side to side, raised and lowered, and

36 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

even turned on its long axis. Two of these muscles are attached at the
base of the plate, one at the front and one at the rear. The other two ex-
tend into the plate for over half its length, and impart the rotational
motion. One muscle extends from the ventral margin of the plate to the
forward part of the basal podomere. The second muscle goes from the
dorsal margin of the plate, passes inside the first muscle, and is attached
to the rear part of the base (Fig. 18). The attachment of the branchial
plate to the socket in the basal podomere is made by very elastic¢ chitin,
and the plate itself is flexible. The rhythmic beating of the branchial
setae can be seen through the shell of the living ostracod, although indi-
vidual setae cannot be distinguished.

The nervous system of the maxilla branches from the ventral chain of
ganglia. There is a large ganglion in the cup of the basal podomere, with
branches into the branchial plate, the palp, and each of the ‘‘mastica-
tory” processes. The ganglion is laterally compressed, but measures about
30u wide and 50pz long.

First TuHoracic LEGS

The first pair of thoracic legs in ostracods of the family Cypridae are
adapted for feeding, and do not resemble the other thoracic legs. Early
workers on the ostracods, noting the resemblance of these first thoracic
legs to the maxillae in form and function, designated them as the ‘“‘second
maxillae.”

In the family Cytheridae there are three pairs of thoracic legs, all
similar and adapted for crawling. Each of these legs is uniramous, and
they appear to be identical.

It is certainly logical, therefore, to assume that the ostracods of other
families also have one pair of maxillae and three pairs of thoracic legs,
rather than two pairs of maxillae and only two pairs of legs. This is now
the accepted interpretation of these appendages.

In the Cypridae the first leg retains the biramous character of the typi-
‘al crustacean appendage. Therefore, the divergence of the Cypridae and
the Cytheridae probably occurred very early in the history of the ostra-
cods. In the former the first leg retains its biramous character but has
been modified in function; whereas, in the latter it has lost the exopodite
but still serves as a walking appendage.

Cypridopsis vidua has an L-shaped protopodite, with the two original
podomeres completely fused and the boundary no longer marked. The
vertical stem is articulated with the rear portion of the hypostome. The
dorsal portion of the protopodite is almost completely rimmed with a
collar of chitin rods. One of these rods on the inner face is modified as a
hook which fits over the tip of one of the loops of the girdle-shaped proc-
ess of the hypostome (Figs. 20, 21). This apparently acts as a fulcrum to

{e) 100u

---chitin process above
the first thoracic leg

flanges
SSN JA
\) protopodite
hook ~
N
a vi exopodite plate
\ 2 /
oe J 4
\ 2
girdle-shaped ----- \ SS h
chitin process :
\! i
hypostome 7 y
% 4
N i f

"masticatory" process of protopodite

Fic. 20. Outer face of left first thoracic leg. The attached chitin process and the
posterior part of the hypostome are also shown.

----- chitin process above
the first thoracic leg

Fic. 21. Inner face of left first thoracic leg, showing the method of attachment
to the hypostome.

38 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

control movement of the leg. This distal end of the protopodite lies more
nearly horizontal and serves as an accessory “masticatory” process. It
is equipped with twelve setae for passing food forward to the mouth.
These setae are spread in a nearly horizontal plane, the longest about 50h
long. When the leg is directed forward, these setae reach to the atrium.

The endopodite is represented by a posterior continuation of the L-
shaped protopodite, giving the whole leg the general form of an inverted
T. This rear endopodite palp is not sharply set off from the protopodite.
It is composed of a single elongate podomere (Plate 71, No. 310). There
are three terminal setae. In syngamiec species of the Cypridae, the endopo-
dite of the male is composed of two podomeres forming a weak chela
used for holding the female during copulation. There is a slight constric-
tion of the endopodite palp of Cypridopsis vidua about 204 from the dis-
tal end, which may represent the setting off of a second podomere; how-
ever, there is no chitin rim to mark the junction, and the writer prefers
to regard the palp as made up of a single podomere.

The exopodite is a plate bearing setae. It is set on to the protopodite
immediately dorsal to the endopodite palp. The five setae have enlarged
bases, and are all about 50» long. They are extremely difficult to see ex-
cept in heavily stained sections (Plate 71, Nos. 310-311). A large, lobed
gland, called ‘gland N” in this paper, empties through a duct, which
passes through the dorsal part of the protopodite of this leg and opens at
the base of the exopodite plate (Fig. 3).

The musculature of the first thoracic leg is very simple. The endopo-
dite palp and the exopodite plate do not appear to have independent
movement. The only muscles apparent in Cypridopsis vidua are attached
to the proximal rim of the leg and connect it to the endoskeleton (Fig.
5). One is fastened to the posterior part of the rim, and the other to the
anterior part. Rome (1945, p. 114) describes additional muscles in the
first thoracic leg of Herpetocypris reptans, some of which are attached
to the dorsal region of the shell. These muscles are either absent or so
inconspicuous in Cypridopsis vidua that they are not discernible in 10u
sections.

The sensory nerves of this leg connect to the ventral chain of ganglia.
There is a broad ganglion in the protopodite, with a branch into the base
of the endopodite palp. This ganghon is very thin, despite its large area
when seen from the side. Nerves from the distal end connect to the “mas-
ticatory” setae.

There is a strong chitin structure dorsal to the first thoracie leg which
is not a part of the leg, but acts as a reinforcing connection from the
first leg to the maxilla. This structure is over 100 long, and is formed
of a long chitin rod shaped like an integral sign, with two median flanges
extending anteriorly (Fig. 20). This chitin process has its base at the

DETAILED DESCRIPTION 39

point where the hook of the leg fits onto the loop of the hypsostome.
Normally it lies almost vertical. The two triangular flanges form a notch
into which the dorsal process of the maxilla fits. This arrangement is
described in the discussion of the maxilla.

The first thoracic legs have the protopodite stems parallel, and nearly
vertical. The ‘‘masticatory” processes at the ends are pointed inward,
and lie ventral to and somewhat inside the processes of the maxilla (Plate
57, No. 270). The endopodite palps are directed outward, and he outside
the bases of the second thoracic legs. A complete needle dissection is
necessary to uncover the details of the chitin rim around the upper part
of the first leg, since it is concealed by the branchial plate of the maxilla
(Fig. 2).

Seconp THoraAcic LEGS

The second pair of thoracic legs are very conspicuous appendages, being
projected out as soon as the shell is opened. They are used in walking
and clinging to inclined surfaces. The powerful end claw can be strongly
flexed, so that the dorsal surface is used to support the rear part of the
body in walking (Fig. 34).

The second thoracic legs were referred to by earlier writers as the first
thoracic legs, since the true first legs of the Cypridae were thought to be
second maxillae.

Each of these second thoracic legs is uniramous. It is composed of six
podomeres, two of the protopodite and four of the endopodite. The proto-
podite is set nearly vertical in the middle of the ventral half of the body,
close to the median plane. The endopodite extends horizontally toward
the posterior end. The terminal claw is curved downward (Fig. 2).

The two podomeres of the protopodite are unique, and partially fused
together. The first has an intricate network of strong chitin rods (Fig.
22). It bulges outward in the middle and enlarges distally to form a chitin
collar which fits around the second podomere (Fig. 23). The entire proto-
podite is firmly attached to the body, and has very limited movement.

The second podomere of the protopodite is hemispherical and fits into
the chitin collar on the distal end of the basal podomere (Fig. 22). It does
not have independent movement, being more or less fused to the basal
podomere, but serves as an area for attachment of many of the muscles
operating the endopodite. There is a small seta on the anterior surface.

The first podomere of the endopodite is strongly constructed and dis-
tinct. It is 60” long and about 45 wide. The proximal rim fits against a
fuleral point on the basal podomere of the protopodite. The ventral mar-
gin bears a fringe of very minute setae, and the distal end has a strong
seta over 50u long.

The second and third podomeres of the endopodite are distinet but

40 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

js podomere of protopodite

2nd podomere of endopodite

fl.
3rd podomere of endopodite

4th podomere
ven of endopodite

terminal

74 s
7 Ist podomere of endopodite 7 clow

Z
2nd podomere of protopodite

Fic. 22. Outer face of left second thoracic leg.

Ist podomere of protopodite
a

Ist podomere of endopodite

4 2nd podomere of endopodite
f / 3rd podomere of endopodite

id “ / th podomere of endopodite
if “ terminal clow

’
dorsal tip

7
2nd podomere of protopodite 0 1004

Fic. 23. Right second thoracic leg as seen from above.

fused together, and act as a single unit. Each has a strong ventral seta
at its distal end. The third also has a small dorsal seta. These podomeres
are laterally compressed to about 15 thickness.

The terminal podomere of this leg is small. Distally it has a large claw
over 100» long and a delicate seta only 30u long. The curved claw serves
as a foot in walking (Fig. 33). It has numerous small teeth along the
ventral margin. The podomere has a ventral chitin projection extending
back inside the third podomere of the endopodite; the flexor muscles are
attached at the end of this projection.

There are two muscles from the protopodite to the endoskeleton (Fig.
5). One is attached to the dorsal tip of the basal podomere, and the other
to the ventral part. Muscles have not been found leading to the dorsal
region of the shell, although such muscles are present for the antennule,

DETAILED DESCRIPTION 41

antenna, and mandible. There is also a muscle from the dorsal tip of the
first to the second podomere of the protopodite (Fig. 22). The presence of
this muscle suggest that the fusion of the two is not complete, and that
there is some little movement possible.

The first podomere of the endopodite is lowered by a broad band of
flexor muscles extending to the anterior area of the second podomere of
the protopodite (Fig. 22; Plate 11, Nos. 53, 56). There is no corresponding
extensor muscle, and the first podomere apparently cannot be raised with-
out moving the second and third podomeres also.

The second and third podomeres of the endopodite are fused together
and act as a single unit. Ventrally they are operated by a flexor muscle
extending to the proximal rim of the first podomere of the endopodite
(Fig. 22). Dorsally they are controlled by extensor muscles connected to
the anterior area of the second podomere of the protopodite.

The terminal podomere and its large claw have great amplitude of
movement. Extended, the podomere lies horizontal with the tip of the
claw pointing downward (Plate 59, No. 272). Flexed, it lies vertical with
the tip of the claw pointing forward (Plate 59, No. 273). When the whole
leg is flexed, the dorsal edge of the claw is turned into a ventral position
(Fig. 33). The terminal podomere is operated dorsally by an extensor
muscle attached to the proximal area of the second podomere of the endo-
podite. The ventral margin of the terminal podomere has a chitin pro-
longation inside the penultimate podomere. Three strong flexor muscles
are attached to this process. The first of these is fastened to the dorsal
part of the proximal rim of the second podomere of the endopodite (Plate
11, No. 55). The other two muscles extend all the way forward into the
second podomere of the protopodite (Plate 34, No. 206).

The sensory nerves of the second leg connect to the ventral chain of
ganglia without an enlargement to form a separate ganglion, such as 1s
present in the antennule, antenna, mandible, maxilla, and first thoracic
leg.

Tuirp THoracic LEGS

The third thoracic legs are the most flexible of all the appendages, and
are used to keep the body and the inside of the shell free of foreign ma-
terials. They are attached to the body immediately behind the dorsal tips
of the second thoracic legs.

Each of these legs is uniramous, and normally hes close to the body in
the form of a modified “U.” The protopodite is directed downward, the
antepenultimate podomere backward, and the penultimate podomere
upward. However, the unusual protopodite cannot only be moved for-
ward, backward, outward, and inward, but can be enrolled on itself a
full 180° to bring the distal end of the leg into the anterior region of the

end claw
|

|
|
\ 3rd podomere of endopodite
Ee
to | 0 1004
1
'

pincers—----

2nd podomere —-----
of endopodite

+-— transverse
chitin process

aN
protopodite

Fic. 24. Inner face of left third thoracic leg.

end claw of terminal podomere ~~

,pincers
?

Fic. 25. Right third thoracic leg enrolled upon itself.

DETAILED DESCRIPTION 43

° 30n
a eee ce aes eae
fl_------ --——frat Em
eit br - —--H-—ex
= 5 ys
endopodite -—-— vat Zo <

|

!

! fl.

'
protopodite

Fic. 26. Inner face of left third thoracic leg showing details of musculature of
the protopodite and the proximal part of the endopodite.

shell (Fig. 25). The terminal podomere and the distal tip of the penulti-
mate podomere act as the two jaws of a pincers, seize small particles of
irritating material, and eject them from the shell. This unique structure
shows the degree of specialization of the ostracod appendages.

The protopodite is difficult to see in the living ostracod, even in species
having transparent shells. It lies under the branchial plate. There are
two podomeres of the protopodite, but they are in an advanced state of
fusion. The line of separation of the two podomeres is marked by the
arrangement of the muscles and by a transverse chitin process on the
inner face, but on the outer face there is no mark of separation at all.
The protopodite acts as a very supple, flexible unit. It is over 100u long.
As stated above, it is able to turn upon itself a full 180° to direct the leg
forward. The inside face of this portion of the leg is characterized by an
intricate frame of chitin rods which control the enrolling motion and
provide a fulerum on which the endopodite pivots. This face bears three
setae: one at the ventral end of the first podomere, one in the middle
of the dorsal area of the second podomere, and the third at the ventral
tip of the second podomere. This last seta may represent the reduction of
the exopodite, but this is a matter of conjecture. The outer face of the
protopodite is made of very thin chitin, with no strengthening structures.

The first podomere of the endopodite is about 100 long and 20u wide.
It bears one well-developed seta at its ventral tip (Fig. 24).

The second podomere of the endopodite is shorter, and bears one long
seta on the middle of its ventral margin. Distally the ventral border is
extended in a tooth-like structure (Plate 60, No. 277). This forms the
lower jaw of the pincers structure. On the dorsal side, the semicircular

44 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

chitin rim is fringed with numerous short, sensory hair-like setae. These
evidently aid in locating foreign materials.

The distal podomere is very short, but quite essential to the function-
ing of the leg. It is joined to the preceding podomere on the dorsal side
by an elastic ligament. The ventral margin forms a chitin hook, which
serves as the dorsal jaw of the pincers. Distally this podomere has a
toothed claw about 25, long. This appears to be used as a kicking struc-
ture to dislodge particles which cannot be easily removed by the pincers.
There is also a short seta attached near the base of this claw. On the
dorsal side of the podomere is a long, backward-directed seta (Plate 60,
No. 277).

The musculature of the protopodite is highly complex. The muscles in
the case of Cypridopsis vidua are quite small in most cases, and cannot
be entirely worked out. Rome (1947, p. 122) has described three groups
of muscles for Herpetocypris reptans which could not be recognized for
this species: first, muscles from the left leg joined to those of the right
on a little chitinous device in the middle of the body; second, muscles
extending to the endoskeleton; and third, muscles extending to the dorsal
region of the valve. There are two muscles of the protopodite which pass
into the body (Fig. 24). These are attached to the distal part of the first
podomere. Two other muscles extend from the proximal rim of the pro-
topodite to the distal part of the second podomere, where they are at-
tached to the chitin framework. They are used in the enrolling process
(Fig. 25). The muscles attached to the dorsal margin may logically be
called extensors, and those attached to the ventral margin may be called
flexors. There is also an extensor muscle from the ventral margin of the
first podomere to the dorsal part of the chitin framework of the second
podomere (Fig. 26). This muscle also assists in the enrolling process, and
is here classified as an extensor because its contraction provides tension
on the dorsal part of the second podomere.

The first podomere of the endopodite has a chitin projection near its
proximal end, which fits against a similar projection at the distal end of
the protopodite (Fig. 26). These form a fulerum to control movement of
the endopodite. A strong muscle is attached to the endopodite proximal
to the fulerum, and extends to the transverse chitin process separating
the two podomeres of the protopodite (Fig. 24). Contraction of this mus-
cle moves the endopodite downward, and it is here called a flexor (Fig.
26). Rome (1947, p. 123) designates the corresponding muscle in Herpeto-
cypris reptans as extensor, apparently because it brings the endopodite
into a straight line with the protopodite, and thus “extends” it. The writer
believes it is much simpler to label all muscles which move podomeres
ventrally as flexors, regardless of the particular angle which the podo-
mere makes with the preceding one. Similarly, all muscles moving podo-

DETAILED DESCRIPTION 45

meres dorsally would be extensors. This plan assumes that the evolution
of a podomere changes the angle it makes with the preceding podomere,
rather than reversing its dorsal and ventral positions. The first podomere
of the endopodite has no extensor muscle, but depends upon the combined
action of the flexor and extensor muscles for the second podomere (Fig.
26; Plate 27, No. 177).

The second podomere of the endopodite is operated by one flexor and
one extensor muscle, both attached to the ventral border of the protopo-
dite near its distal end (Fig. 24).

The terminal podomere is operated by a single muscle, which acts as an
adductor to close the pincers.

The sensory nerves from the third leg are attached to the ventral chain
of ganglia, and do not have a separate ganglion. Separate nerves from
the upper and lower jaws of the pincers unite in the protopodite (Fig. 6).

GENITAL LOBES

The external chitinous parts of the genital system are generally im-
perfectly understood. The lobes themselves are half ellipsoids set side by
side near the median plane. They le behind the thoracic legs and in front
of the furcae.

The key to the arrangement of the whole genital system is the fact
that there are two pairs of genital openings. The two vaginal openings lie
near the center of the lobes, on the inner faces, and are rimmed with
heavy chitin frames. In syngamic species they are used in copulation,
and lead to the seminal receptacles. There are separate distinct uterine
openings, through which the eggs are discharged. They are normally very
long horizontal slits along the inner edges of the genital lobes, extending
behind the vaginal openings (Fig. 27). In the process of egg laying, the
genital lobe is forced outward to provide a sufficiently large opening.

The vaginal opening has a rather complex chitin structure. The opening
itself is directed toward the posterior end of the animal. It has an ellip-
tical frame (Fig. 28, alpha and beta), which is joined at its dorsal and
ventral tips by a semicircular rod of chitin which arches toward the
anterior end (Fig. 28, gamma). This strengthening rod lies along the
inner face of the genital lobe, and near its ventral juncture with the frame
of the opening it is divided to form a hole (Fig. 29). A separate chitin
structure extends through this hole, curved like a buckle. Bergold (1910,
p. 28) described this as a chitin “stick,” and that designation is used here.
The outer edges of this chitin “stick”? are marked by small pustules, to
which muscles are attached to operate the vaginal openings. The muscles
connect to the outer ventral wall of the genital lobe. Their contraction
pulls the chitin “stick,” which then turns the framework of the opening.
In a syngamic species, this would make it more accessible for the male in

46 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

_ genital lobe
---chitin "stick"

—chitin frame of
vaginal opening

/ —bose of furca
-— uterine opening

—-rod acting os fulcrum
for the furca

a
Al

0 100zu

Fig. 27. Genital lobes and posterior portion of the body as seen from below and
to the rear. Distal portions of the fureae are removed to show the vaginal open-

ings.

Fic. 28. Chitin framework of the right vaginal opening as seen from below.

copulation. The “stick” is enclosed by the genital lobe (Figs. 3, 4; Plate
49, No. 241; Plate 59, No. 272).

The pair of uterine openings are not nearly as conspicuous as the vagi-
nal openings. They are elongate in the long direction of the animal, and
lie immediately anterior to the fureae (Figs. 3, 4). The actual opening
is difficult to find in microtome sections, being closed except during the
period of egg laying. In those specimens having eggs in the end sections
of the uterus, the opening is distended and can be located accurately
(Plate 39, No. 221; Plate 40, No. 222; Plate 50, No. 243). The uterine
openings are operated by numerous muscles attached to the periphery,
and connected to the genital lobe and to the posterior body wall (Fig. 4).

DETAILED DESCRIPTION 47

furca
‘genital lobe

*%
vaginal opening

Fic. 30. Inner face of right furea.

The sensory and motor nerves are connected to the posterior part of
the ventral chain of ganglia (Fig. 6).

FURCAE

The pair of fureae are attached to the posteroventral part of the body,
immediately behind the genital lobes. Many of the fresh water ostracods
possess furcae which are very strong and each is equipped with robust
claws. However, the subfamily Cypridopsinae, to which Cypridopsis vi-
dua belongs, is characterized by reduced fureae, each of which terminates
in a long seta or “flagellum.”

The furea apparently serves only a sensory function in Cypridopsis
vidua. The base is about 50 long, and tapers gradually for about three-
fourths of its length, then more sharply until it is only a few microns at
the point where it joins the terminal seta. This long seta is about 80,
long, and tapers throughout its length to a very delicate tip (Fig. 30;
Plate 50, Nos. 242, 248). There is a second small seta 20” long on the

48 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

dorsal edge of the base, attached at the point where the tapering of the
base changes abruptly.

There is a vertical chitin rod fitted against the mid-point of the base of
the furea, which acts as a fulerum. This rod is curved around the posterior
part of the body, embedded in the body wall. Dorsally the rod splits into
two branches. The posterior branch is a place of attachment for muscles
operating the furea (Fig. 5).

Nerves of the furea are connected to the posterior end of the ventral
chain of ganglia.

THE EYE

The “single” eye of the ostracod is not a simple organ. It is made up
of two lateral elements and one median. It hes in the most anterior-part
of the body a little below the dorsal rim of the shell. When the shell is
gaped open, the eye can see through the space between the valves, with
only the body wall of the forehead to interfere with the vision. When the
shell is closed, however, direct vision is sacrificed for protection. Even
under such adverse circumstances, the animal is able to distinguish light
from shadow.

The framework of the entire eye structure is black and opaque. This
pigment forms a backdrop for the three parts of the eye, so that the
sensitive cells in each can receive light only from a given direction.
Three optic cups are set into deep depressions in the pigment, one on each
side, and a third slightly below and at the front. Each of these optic cups
has a tapetum and is equipped with sensitive nerve cells. In each lateral
cup the tapetum forms two basins to accommodate the twin lenses. The
number of sensitive cells can be determined, provided the specimen is
prepared carefully, oriented precisely, and cut in very thin sections.
The writer did not attempt the exacting procedure. Novikoff (1908, p. 85)
reported ten to fifteen cells in each of the lateral cups and seven to eight
in the frontal cup. Rome (1947, p. 79) counted the sensitive cells in the
eye of Herpetocypris reptans as follows: the frontal cup = 8, upper part

of posterior basin of each lateral cup = 6, lower part of the posterior
basin of each lateral cup = 4, and anterior basin of each lateral
cup: = 3;

The crystalline lenses of the eye serve to concentrate the light onto
the sensitive cells, and also to anchor the eye in place. The frontal cup
has a single large lens, which in Cypridopsis vidua is heart-shaped, with
two dorsal lobes (Plate 61, No. 282). Each lateral optic cup contains two
lenses. These are rounded, except for the flat surfaces where the two are
in contact, and for the elongate projections which hold the eye in place.
There are four projections, one on each of the lateral lenses. The two
anterior projections diverge and end at the forehead, near the inside

DETAILED DESCRIPTION 49

boundaries of the antennules (Plate 61, No. 281). They are attached,
and it is possible that the eye can be moved slightly by the movement of
the antennules. The two posterior projections diverge toward the rear,
and are embedded in the connective tissues of the head (Plate 20, No.
134).

There are three optic nerves connecting the nerve cells of the eye
with the protocerebrum. There is one from the frontal median element
(Plate 15, No. 85; Plate 42, No. 226), and one from each of the two
lateral elements (Plate 15, Nos. 86, 88; Plate 42, No. 227). These nerve
cords are very smooth and cylindrical.

E-NDOSKELETON

The endoskeleton is completely encased within the body, and therefore
can be studied only by sections. Although the endoskeleton was properly
described by Claus (1893, p. 57) and by Vavra (1891, p. 11), its nature
was misunderstood by Khe (1926, p. 10) who confused it with the frame-
work of the body.

The muscle arrangement in the ostracod differs from that in the higher
crustaceans. In the lobster, for example, the appendages of each segment
are operated by muscles attached to the surrounding section of hardened
carapace. In the ostracod, however, the hardened armor is in the form
of the two valves of the shell; and the wall of the pouch-like body hang-
ing inside the shell is, for the most part, very delicate and supple and
structurally unsatisfactory for muscle attachment. These factors critic-
ally limit the pattern of muscle arrangement. Many muscles from the
appendages are attached to the dorsal region of the shell; some of the
muscles from the alimentary tract are attached to a framework of chitin
rods embedded in the body wall; and other muscles from the appendages,
alimentary tract, and excretory glands are fastened to the endoskeleton
in the middle of the body.

The endoskeleton is composed of chitin. It lies behind the esophagus,
above the ventral chain of ganglia, and between the mandibles. There
are projections from the plate-like center of the endoskeleton pointing
toward the various appendages. Muscles are attached at the ends of
these projections. The projections toward the antennules and antennae
are fused into wing-like processes extending outward and upward (Plate
64, No. 288; Plate 69, No. 303). There is also a posterior ventral exten-
sion to which the muscles of the maxilla and the first thoracic leg are
attached (Plate 70, No. 306).

The endoskeleton itself is suspended by a pair of muscles from the
dorsal region of the shell (Plate 11, No. 54). The contraction of these
muscles compensates the forces exerted on the endoskeleton by the other
muscles (to appendages, hypostome, ete.).

50 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

There are muscles from the endoskeleton to the antennules, the anten-
nae, the mandibles, the esophagus, the hypostome, the maxillae, the first
thoracic legs, the second thoracic legs, excretory gland A’s, excretory
gland C’s, and the closing muscles. This last muscle, connecting the endo-
skeleton with the closing muscles of the shell, is a subject of controversy.
Rome (1947, p. 83) denied its existence. There are muscles from the
endoskeleton which appear to terminate at the junction of the closing
muscles with the chitin process which joins closing muscles of the oppo-
site sides (Plate 63, No. 286; Plate 23, No. 147). These muscles lie above
those going to the maxillae, and are definitely attached to the endoskele-
ton. The writer is of the opinion that they are also attached to the chitin
process joining the closing muscles of right and left sides, as Vavra
(1891, p. 11) and others believed.

The writer has also examined sections of Candona crogmaniana Turner,
which has a markedly different endoskeleton. In this case it has a com-
plex net of delicate chitin rods, with no such large masses of chitin as are
present in Cypridopsis vidua. The endoskeleton probably differs with
each species.

EXxcrETorRY GLAND A — THE GLAND OF THE ANTENNULE

The excretory glands lying on the sides of the esophagus and in front
of the ducts from the liver to the stomach are conspicuous structures in
frontal sections, but they were not described until 1910, when Bergold
(1910, p. 12) gave a very good account of them. They le within the
limits of the body, and empty out immediately below the antennules
through a duct. Since Bergold referred to the antennules as the “first
antennae,” he called these the “glands of the first antennae.”

The glands are not located in the antennules (“first antennae’’), and
there is no evidence that their functioning benefits these appendages any
more than any other part of the body. Each of them is here called simply
an “excretory gland A,” to distinguish it from other excretory glands.

Each gland is roughly triangular in shape and spread out horizontally.
It is about 30, in its longest direction, and has a duct 20» long (Plate
3, Nos. 10-12; Plate 22, No. 144; Plate 65, No. 290). It contains four or
five large cells, each containing several small nuclei. No fluid has been
observed in the cavity.

A large muscle is attached to the posterior point of the gland, leading
back to the endoskeleton (Fig. 4; Plate 3, Fig. 11; Plate 15, Fig. 89).
Contraction of the muscle stretches the gland, narrows its diameter, and
forces out any secretion it may contain.

EXcrRETORY GLAND B — THE “SHELL GLAND”

This pair of glands is very complex, and may actually represent the
combination of two pairs of glands. They are located in the epidermis of

DETAILED DESCRIPTION ol

the shell, and in many species can be seen through the shell. They are
seen with difficulty in living Cypridopsis vidua because of the color pat-
tern on the shell.

These glands were first recognized by Zenker (1854, p. 38), who re-
ferred to them as Milz (spleen). His description was incomplete. Claus
(1895, p. 13) gave complete details of the gland, and compared the strue-
ture in various Cypridae. Additional contributions were made by Ber-
gold (1910, p. 13).

The “shell glands” of the ostracod appear to be homologous to the
green glands of the higher crustacea and to the shell glands of the Cla-
docera.

Each gland is composed of three parts: a glandular duct with several
lateral diverticula; a rear sac which empties into the inside (at the junc-
tion of the base of the antenna with the hypodermis of the shell) through
a short duct; and an end sac of secreting cells, connecting to the rear
sac through a narrow duct (Fig. 31).

The glandular duct is the largest of the three parts (Fig. 1). It
lies entirely within the hypodermis, anterior to the body (Plate 3, Nos.
10-12; Plate 8, No. 39; Plate 14, Nos. 81-83; Plate 42, No. 227). It has
eight to ten short diverticula which increase the volume of the lumen.
The cells surrounding the duct have large oval nuclei (Plate 32, Nos. 197,
198), and number about eight in Cypridopsis vidua. They seem to bear
no particular arrangement with respect to the diverticula, sometimes
being located at the ends, and at other times lying between adjacent di-
verticula. The cells around the glandular duct are set off from the epi-
dermal cells and are connected to the walls of the epidermis by trabecular
processes. Claus (1895, p. 14) referred to the spaces in the hypodermis
as blood lacunae. No fluid has been seen in the glandular duct of Cypri-
dopsis vidua, but the writer also examined sections of Candona crog-
maniana Turner, in which the diverticula are found to be partially filled
with a clear substance which stains an orange color with Ehrlich’s haema-
toxylin and eosin.

The rear sac of the gland is an ellipsoidal cavity about 40 in diameter.
The glandular duct empties into it with no apparent change in diameter.
The rear sac lies posterior to the junction of the hypodermis lining with
the body wall, with about half its volume extending into the region of
the body (Plate 1, Nos. 3, 4; Plate 15, No. 87; Plate 20, No. 135). The
four or five cells forming the rear sac are large and each contains several
nucleoli. The sac also has an enveloping meshwork of fibrous processes.
The end sac also empties into this rear sac through a narrow canal
(Fig. 1). The rear sac discharges the products it receives from the glandu-
lar duct and the end sac through a short tapering duct which opens be-
tween the antenna and the lining of the shell. This duct is difficult to
find except in transverse sections (Plate 15, No. 85). The emptying of

LIBRARY
UNIVERSITY OF ILLINO!S

52 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

{e) 50u
muscles | | |
1\
a

rear sac

l
|
|
1
|

end sac

Fic. 31. Ten-micron longitudinal section through excretory gland B. The right
side of the drawing is anterior.

the rear sac is accomplished by two small muscles attached to the postero-
dorsal part connecting it to the wall of the hypodermis (Figs. 1, 31).

The end sac is located immediately anterior to the liver, to which it is
connected by tissue (Plate 2, No. 7; Plate 32, No. 196). It is composed
of about six large cells with circular nuclei, which stain the same color
as the cells of the liver. The lumen is very narrow. It connects to the rear
sac by a narrow canal about 30n long (Fig. 31).

It is impossible at this time to tell what the evolutionary history of
excretory gland B has been. It apparently corresponds to an original
segmental nephridium. The end sae seems to be an added feature. The
boundaries of the ancestral segments have disappeared in the ostracod,
and the development of the shell has influenced the arrangement of the
body elements. Only three of the numerous nephridia in the ancestor have
survived. One of these, the one under discussion in this section, is lo-
cated almost entirely in the hypodermis of the shell. Certainly this gland
deserves additional study, for it quite possibly holds the key to the
history of the ostracod shell.

Excretory GLAND C — THE MAxILLARY GLAND

This gland was first described by Bergold (1910, p. 18). The sole rea-
son for calling it a ‘maxillary gland” is that the orifice is located im-
mediately behind the maxilla. The ostracod has no segmental boundaries

DETAILED DESCRIPTION 93)

and the number of appendages are reduced from that of other crustacea,
so there is no assurance that this nephridial structure is actually part of
the maxillary segment. It is here called excretory gland C.

There is a point of confusion which should be clarified for other work-
ers in ostracod morphology, in case it has not already been discovered
by them. The term “maxillary gland” has been used for two entirely
different structures. The term is referred to in this paper as it was ori-
ginally applied by Bergold. However, Yatsu (1917, pp. 435-39) Okada
(1926, p. 478), and possibly others have used the term “maxillary glands”
for some elongate glands in the upper lip of certain marine ostracods.
These glands are the source of the bioluminescence which characterizes
these species. The glands were first discovered by Miller (1890, p. 248-
49), who described them only as glands in the upper lip. His description
and illustrations depict them as large, elongate glands filling most of the
upper lip. They empty individually through pores in the outside ventral
wall of the upper lip. Some of these pores are located on odd cone-like
projections. The illustrations of both Yatsu and Okada leave no doubt
that they were describing these glands. It is unfortunate that they
selected “maxillary glands,’”’ a term already in use and also very inap-
propriate as applied to glands which produce luminescent substances.
No homologous glands have ever been found in fresh-water ostracods.

The pair of these glands is found near the center of the body behind
the closing muscles. Each gland lies immediately to the outside of the cor-
responding gland N (Plate 63, Nos. 285, 286; Plate 64, Nos. 287, 288).
The gland is foursided in frontal section (Plate 64, No. 287), roughly
circular in sagittal section (Plate 10, No. 47; Plate 27; No. 178), and tri-
angular in transverse section (Plate 17, No. 98). From these sections we
can construct the general form as that of a truncated pyramid which is
almost completely inverted. The two outside corners of the gland are
affixed to the body wall, and the posterior inside corner is anchored by
branching tissues which penetrate into the interior of the body (Plate 64,
No. 287). The fourth corner, the inside anterior, is attached to muscles
leading to the nearby endoskeleton. The anterior portion of the gland
narrows downward into a tiny duct, which is contorted in a flattened
S-shape (Fig. 3; Plate 64, Nos. 287, 288; Plate 65, No. 289). The orifice
of this duct is in a slight indentation of the body wall immediately be-
hind the maxilla. The contraction of the muscle to the endoskeleton nar-
rows the lumen of the gland and forces the contents out through the
ventral duct.

The cells of this gland are the same type as those composing excretory
eland A and the rear sae of excretory gland B. The several nucleoli of
each cell are small and inconspicuous. No substance has been observed in
the lumen of the gland.

54 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

THE LIVER OR HEPATOPANCREAS

The livers or hepatopancreases are paired glands lying in the hypo-
dermis layers of the valves and emptying their solution into the stomach
through ducts. They secrete a large portion, if not all, of the digestive
juices.

Each of these large glands is nearly 200u long and 40» in diameter in
the posterior half (Plate 8, Nos. 35-37). The anterior half extends hori-
zontally to a width of over 60u (Plate 1, No. 4). The posterior end is in
the posteroventral quadrant of the hypodermis, from which point the
liver curves upward and forward until the anterior end is at the side
of the stomach (Fig. 1). There is a large lumen which is always partially
or wholly filled with fluid. The short, horizontal duct from the lumen
tapers to a small orifice in the front part of the stomach (Plate 2, No. 6).

The food ball in the stomach is surrounded by a substance which shows
the same properties as that in the livers, and there is no reason to doubt
that they are the same. The large blocky cells of the liver have large
nuclei, and differ from the narrower elongate cells of the stomach wall.
This strongly suggests that the liver produces all of the digestive fluids,
while the stomach absorbs the nourishment of the food.

GLAND L — GLAND OF THE UPPER LIP

This pair of glands was first described by Claus (1895, p. 12). They are
located in the upper lip and open to the rear in the mouth, near the place
where the atrium narrows into the esophagus (Plate 6, Nos. 21, 22; Plate
14, Nos. 78, 79; Plate 24, No. 150; Plate 30, No. 188; Plate 34, No. 206).

Each gland is about 30» in diameter, roughly spherical in shape, and
set in the center of its half of the upper lip. There is no large lumen, and
the duct leading to the mouth is small and made of thin tissue. The gland
is held in place by this duct and by a thin connective tissue extending to
the anterior wall of the upper hp. The wall of the gland is very definite
in cross-sections, but in the whole animal it is sometimes obscured by ~
subdermal cells which have the same appearance as the cells of the
gland. The cells of the gland can be seen more easily in a needle dissec-
tion of the whole animal than in any of the sections, due to the strong
absorption of stain in the outer parts of the gland. In a needle dissec-
tion the cells’ borders can be seen, showing about eight cells. Each cell
has several small nucleoli.

Gland L is one of the few glands of the ostracod which suggests a spe-
cific function by its location. Whatever solution is produced, it is emptied
into the mouth. The gland might be called the salivary gland without
gross error of judgment. The food upon reaching the stomach is immedi-
ately embodied in a smooth, ellipsoidal mass, the food ball (Plates 1, 2).

DETAILED DESCRIPTION 55

What role the fluid secreted by gland L plays in preparing the particles
for incorporation in the mass already in the stomach is only a matter of
conjecture, at present.

“Gruanp M” — THE GLAND (?) OF THE MANDIBLE

Schreiber (1922, pp. 530-31) described an unusual gland which had
not been previously recognized, located in the distal portion of the basal
podomere of the mandible. This multiple gland, according to the deserip-
tion, is composed of about thirty small glands, each consisting of a single
cell, all enclosed by a loose membrane. Most of the cells lie clustered in
the dorsal part of the glandular structure, but several are isolated in the
ventral part. Each cell has a tiny duct leading down from it. Three or
four of these ducts open above the constricted part of the toothed area,
but the majority of them converge into ducts opening to the outside
through circular openings in the teeth (according to Schreiber).

Schreiber’s original description of these cells compares them with those
of Dytiscus marginalis, as described by Casper (1918, p. 443). These
cells form a mandibular gland. Dytiscus is a predaceous diving beetle.
Now, although the ostracod and the diving beetle belong to the same phy-
lum, and both are freshwater forms, we should use extreme caution in
stating that structures are homologous. Indeed, the ostracod is such a
modilied little animal that it is difficult to make certain direct compari-
sons with the higher crustaceans (Malacostraca), to which it is more
closely related.

The arrangement described by Schreiber is present in Cypridopsis vidua
(Plate 6, No. 24; Plate 35, No. 209; Plate 43, No. 229). There are small
elongate cells about 1144 to 2 in diameter located dorsal to the mandi-
bular teeth, with little cord-like connectives less than ‘gp in diameter
converging and extending into the teeth. However, the writer has seen
no openings for these small connectives; and whether the connectives are
nerve fibers (as they appear to the writer) or are tubular ducts (as
Schreiber believed) is not critically defined in 10 sections with a mag-
nification of 850 diameters. The “gland” cells stain the same color as the
nerve cells with Ehrlich’s haematoxylin and eosin. Cells of gland N and
gland O show much darker borders and more granular protoplasm with
the same treatment. So the cells in question appear to be sensory nerve
cells, with nerves extending into the teeth.

Rome (1947, p. 105) studied the cells in the mandible of Herpeto-
cypris reptans and concluded that the structures were scolopoides, with
the terminal filaments ending in the teeth and setae at the distal end of
the basal podomere.

The writer uses the term “gland M” in this paper. He does not believe
Schreiber’s theory, and he agrees with Rome in that the cells are nerve

56 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

cells. Detailed work is needed to determine the nature of the distal ends of
the nerve fibers, and whether there are any openings in the teeth. Thinner
sections and higher magnifications with the electron microscope may
bring additional evidence as to what particular sense is registered by
this group of cells.

GLAND N — THE GLAND OF THE First THORACIC LEG

Each of this pair of glands les in the middle of the body behind the
closing muscles and the endoskeleton, on the inner side of the correspond-
ing excretory gland C. The two N glands lie side by side next to the
median plane (Plate 638, No. 286). Claus (1895, p. 18) gave the first
account of this gland in 1895, calling it the Kieferdriise (gland of the
jaw) to correspond to his term for the first thoracic leg, Kieferfuss (jaw-
foot).

Each gland is reniform, slightly lobed, with distinct borders. It is
about 30 in diameter. The two inner lobes extend above the ventral
chain of ganglia (Plate 10, No. 52; Plate 24, Nos. 150, 151). There is a
distinct duct in the center of the gland (Plate 64, No. 288), which ex-
tends beyond the glandular section into the shaft of the first thoracic leg
(Plate 5, No. 19) and opens at the base of the exopodite plate of that
appendage (Fig. 3).

There are apparently no muscles attached to this gland, so that it is
not comparable with the nephridial structure of the excretory glands. The
internal structure in the case of Cypridopsis vidua differs from that of
other Cypridae. The cell boundaries are not distinct, the glandular por-
tion appears granular, and the nuclei are obscured by the very dark outer
area, which becomes opaque with absorbed stain (Plates 638, 64). The
writer has examined sections of Candona crogmaniana Turner for com-
parison, and found that the gland in that species has very obvious cell
boundaries and large nuclei set toward the outer wall away from the duct.

The nature of the secretion and its utilization are unknown. The de-
velopment of this gland varies in individuals. Further investigations
could be made by isolating individuals of the eighth instar into differing.
environments where factors of pH of the water, temperature, types of
food available, light, ete., are controlled. As soon as the animals had
molted into the adult stage, and survived for a given period, they could
all be killed and sectioned, and the glands examined. In that way, per-
haps, the function of this and other glands could be determined, or at
least logically conjectured.

GLAND O — THE COPULATION GLAND

This gland was described first by Bergold (1910, p. 28), and later by
Fassbinder (1912). The two accounts do not agree in all details.

DETAILED DESCRIPTION 57

The gland is very well developed in Cypridopsis vidua, even though
it is a parthenogenetic species (Plate 4, No. 13). It is elongate, about
30u in diameter and 50u long (Plate 48, Nos. 238, 239; Plate 49, No. 240).
It lies above and outside the vaginal opening to which it is connected by
a duct. The writer has a section where an egg is in the lower part of the
uterus, adjacent to the gland (Plate 51, No. 245; Plate 52, No. 246).
There does not appear to be any duct connecting the uterus with the
gland, as was described by Fassbinder (1912, p. 567: “. .. geht der Eileiter
aus einem sehr engen Abschnitt in einem viel umfangreicheren drisigen
Teil ber, welcher der von Bergold beschreiben Copulationsdriise ents-
pricht.”) In frontal section this gland is seen to have a distinct lumen
(Plate 40, No. 222). The boundaries of each cell are somewhat irregularly
disposed. The protoplasm is granular in appearance, and the nucleus con-
tains several nucleoli.

The use of gland O is not known. Its secretion may be of some value in
copulation, as Bergold suggested. Although it appears well developed in
a parthenogenetic species, such as Cypridopsis vidua, we cannot say
that it is not copulatory in function, for we know that disuse is not neces-
sarily accompanied by the reduction and disappearance of an organ. The
writer has not seen any duct connecting gland O to the uterus, so Fass-
binder’s suggestion that the gland secretes the shell of the egg seems
highly improbable. For the secretion to reach the uterus, it would have to
pass successively through the duct of gland O, the “copulation bladder,”
out through the vaginal opening, and into the uterine opening. Additional
research is needed, particularly with the larger Cypridae, to establish the
finer details of this gland.

THE DIGESTIVE SYSTEM

The ostracod has a complete system of digestive organs from the mouth
to the anus. This includes the atrium (mouth), esophagus, stomach, in-
testine, rear gut, and anus.

The atrium is bounded on the two sides by the toothed ends of the man-
dibles, on the front by the upper lip, and on the rear by the hypostome.
The mandibles have a masticatory and rasping action in preparation of
food particles, and can actually “bite off” pieces of solid material. Most
of the food, however, consists of numerous fine particles of algae passed
into the mouth by the mandibular palps, the maxillae, and the first
thoracic legs. Some accessory chewing action is accomplished by the rake-
shaped organs embedded in the front of the hypostome. Very small par-
ticles are probably obtained by straining through the curtain of long
hairs which reaches to the median plane from the front edges of the hy-
postome. It is quite possible that the animal can selectively route the
food either to go through or to by-pass this strainer. The hypostome can

58 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

move forward and back; and although the upper Hp is rigidly attached
to the head, the Y-shaped chitin process at the front of the atrium can
also move forward and back (Fig. 4). Gland L, probably a salivary
gland, empties into the upper part of the mouth (Fig. 3).

The esophagus is a very muscular portion of the tract. Muscles com-
pletely encircle the opening (Plate 5, No. 19). There are also muscles to
the forehead, upper hp, and endoskeleton, which by their contraction can
distend the opening (Fig. 4; Plate 10, No. 52; Plate 11, No. 53).

The esophagus opens into the stomach. At the place of entrance there
are two structures which serve to move the food quickly into the stomach.
The first is a powerful tongue-shaped organ which Claus (1895, p. 5)
described as a Wulst (swollen hump), and Bergold (1910, p. 5) referred
to it as a dorsaler Wulst. The writer has retained this very appropriate
term for this structure. The dorsal wulst projects to the rear, and fits
closely against a corresponding structure called the “ventral wall of the
front stomach” or the ‘‘ventral duplicature.” This feature has a concave
front surface, however. A cross-section of the passageway between them
is crescentshaped, with the horns of the crescent pointed forward (Plate
3, No. 12).

The dorsal wulst is surrounded by a hard cuticle bearing rows of small
hairs. These hairs (miniature setae) are directed upward, and push the
food particles into the stomach. There is a median groove in the free
upper end of the dorsal wulst (Plate 3, No. 9). The dorsal wulst is oper-
ated by powerful muscles extending to the front wall of the upper lip
(Plate 10, No. 52); these muscles have been referred to in the literature
as “pharynx muscles.” Other muscles extend across the base of the struc-
ture (Fig. 4). In immature individuals or in adults which have recently
molted, the bobbing motion of the dorsal wulst can be seen through
the shell.

The ventral duplicature is much smaller than the dorsal wulst, but is
similarly armed with a hard cuticle bearing setae. It is attached at its
front end, with the rest of the structure hanging free (Plate 10, No. 51;
Plate 34, No. 205). Two sets of small muscles cross the basal part (Fig.
4), one from the esophagus to the rear wall of the structure, and the other
from the stomach wall to the front part of the structure.

The stomach is a large organ in which most (if not all) of the digestion
takes place. It is suspended from the dorsal part of the shell by a bundle
of tissues (Plate 10, No. 49; Plate 29, No. 184). Ducts from the two
livers enter the front part of the stomach from opposite sides (Plate 2,
No. 6). The walls of the stomach are made of three layers. The outer-
most is a thin layer of longitudinal muscles; the middle is a thin layer
of circular muscles; and the innermost is a thick layer of epithelial cells.
This lining is the true digestive layer, and is made up of cylindrical to

DETAILED DESCRIPTION 59

prismatic cells filled with very finely granular protoplasm. The cell
walls are distinct, and the nucleus les in the outer half of each cell. These
cells are altered considerably by prolonged dessication in alcohol, and the
best sections are those most quickly prepared. Although the liver secretes
most of the enzymes used for digestion, the epithelial lining of the stom-
ach may also contribute substances to act on the food. A food ball in
the stomach is always surrounded by digestive fluid, but in the rear gut
there is seldom a vestige of such fluid. It is possible, however, that some
resorption of nourishment continues in the rear gut portion of the ali-
mentary tract.

There is a short section where the tract is constricted and surrounded
by heavy muscles, which is here called the intestine. Here the longitudi-
nal and circular muscles are to be seen in their fullest development (Plate
1, Nos. 2-4). The movement of the food ball from the stomach to the
rear gut is quite as involved a procedure as the final voiding through the
anus. Different specimens have shown the following three conditions:
(1) food ball in the stomach only (rare); (2) food balls in both the
stomach and rear gut (usual case) (Plate 2, No. 6; Plate 10, No. 48); and
(3) food ball in the rear gut only (Plate 33, No. 203). This suggests that
the feeding and digestive processes are not continuous, but periodic, al-
though the animal appears to spend most of its time grazing on algal
growths.

The rear gut is a cavity lined with the same kind of epithelial cells as
the stomach, though not so well developed. Some resorption of nutrition
may take place here, but the food balls (changing to fecal pellets) are
noticeably smaller than those in the stomach.

The anal opening is an elongate slit made of soft thin chitin (Plate
38, No. 219). It is not muscled at the termination, and the muscles acting
as a sphincter lie at the end of the rear gut (Plate 10, No. 49).

THE Nervous SYSTEM

The main features of the nervous system are quite obvious in all stained
sections. The central portion consists of the well-developed cerebrum, a
circumesophageal ganglion, and a ventral chain of fused ganglia. There
are also small ganglia in the antennules, antennae, mandibles, maxillae,
and first thoracic legs which are connected to the central portion of the
system. There is also a network of small motor nerves from the central
portion connected to the various muscles.

The cerebrum has been studied in detail by Turner (1896, pp. 20-44)
and later by Hanstrém (1924, pp. 31-388). It is divided into three portions
which can be discerned only by a study of the nerves, for they are not
marked off by any constrictions. These three portions are the protocere-
brum, the deutocerebrum, and the tritocerebrum.

60 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

The protocerebrum is located in the forehead above its junction with
the upper lip. It is gently rounded at the top and enlarges downward
to the deutocerebrum. The sensory nerves leading into the protocerebrum
are the three optic nerves, one from the frontal optic cup and one to
each of the two lateral optic cups (Plate 14, Nos. 83, 84; Plate 42, Nos.
226, 227).

The deutocerebrum lies below the protocerebrum. The front is blunt
and two wings extend outward toward the rear (Plate 68, Nos. 299, 300).
There are two pairs of sensory nerves leading into this portion of the
cerebrum. The first pair comes from the antennules (Plate 10, No. 52;
Plate 42, No. 227), and the second pair comes from a network of sensory
nerves in the anterior part of the shell. The latter pair is difficult to fol-
low in sections, but apparently enters into the epidermis of the valves
in front of the duets which connect the livers and the stomach. There
are also motor nerves leading out from the deutocerebrum to the anten-
nules and the dorsal region of the body.

The tritocerebrum has a flattened front with two small forward-
projecting ridges at the sides and large extensions outward toward the
rear (Plate 68, No. 301; Plate 69, No. 302). Sensory nerves from the
antennae lead into the tritocerebrum (Plate 69, No. 303).

The cirecumesophageal ganglion is composed of two connectives between
the cerebrum and the ventral chain of ganglia, one on either side of the
esophagus (Plate 23, No. 147; Plate 29, No. 185; Plate 48, No. 229; Plate
69, Nos. 303, 304). Motor nerves extend upward to the antennae and
frontal region and downward to the upper lip (Fig. 6).

The sensory nerves of the upper lip are joined to a second ring of nerve
tissue around the esophagus, the peribuccal ring (Fig. 6). This ring is
attached to the central nervous system at the junction of the cireum-
esophageal ganglion and the ventral chain of ganglia.

The ventral chain of ganglia begins anteriorly with a subesophageal
enlargement and tapers posteriorly to the fureae, with local enlargements
between each pair of postoral appendages (Plate 11, No. 53; Plate 15, No.
86; Plate 34, No. 206). The anterior end of the ventral chain lies below
the endoskeleton, and has a hole in the middle to accommodate the mus-
cles from the endoskeleton to the hypostome (Plate 70, Nos. 306, 307).
Sensory nerves join the ventral chain from the mandibles, the maxillae,
the thoracic legs, the posterior portion of the valves, the genital region,
and the furcae. There are also motor nerves extending out to the muscles
of the oral and postoral regions of the body (Fig. 6).

THE VALVES

The body of Cypridopsis is enclosed by two valves which are hinged
together along the middle one-third of the dorsal margin. These two

DETAILED DESCRIPTION 61

valves are very nearly alike, but are not exact mirror images of each
other. There are small differences to be seen on close inspection, as will
be described later.

The two valves are closed by muscles through the center of the body.
When these muscles relax, the elastic hgament on the dorsal margin has
the tension released upon it and contracts, pulling the valves open. When
the valves are thus gaped open, the appendages can be thrust out of the
boundaries of the shell for locomotion, feeding, and other life processes.

Each valve is composed of two major divisions: (1) a layer of soft
sensitive tissues called the epidermis or hypodermis, enclosed by chitin,
and (2) a layer of hard calcium carbonate coated with chitin. This latter
layer forms the so-called outer lamella, bounding the epidermis on the
outside, and the adjoining duplicature, rimming the inside edge of the
epidermis (Fig. 32).

Many writers have methodically described the hard parts of the valves
first. Perhaps this approach has been induced by two facts: (1) the hard
parts of the shell are taxonomically the most important parts of the ani-
mal, and (2) they are the parts preserved as fossil. In their enthusiasm
over the hard parts, some writers have even chosen to regard the epi-
dermis as an incidental layer of tissue filling the space between the hard
parts on the outside and a lamella of chitin on the inside. This is faulty
analysis. It has led to unfortunate choices in terminology which make it
difficult to understand the true nature of the valves.

A more logical order of discussion is called for. It must be borne in
mind that each time the animal molts, the caleareous and chitinous parts
of the valves are shed, and only the soft epidermis remains with the
animal as a basic and necessary part of its anatomy. The epidermis is
the stable part of the shell in the ostracod’s ontogeny. It determines the
form of each new set of hard parts which it secretes. Therefore, the
study of the shell should begin with the epidermis, and the calcareous and
chitinous layers should be described in their relation to it.

THE EPIDERMIS OR HyPODERMIS

Claus (1893, p. 17) described the soft tissues in each valve as a hypo-
dermis composed of two layers, an outer and an inner. Fassbinder (1912,
pp. 566-67) referred to the same tissues as an outer hypodermis and an
inner hypodermis. Rome (1947, p. 68) calls them an epidermis with two
layers of epithelial cells. Although the terminology is varied, most writers
agree on the actual anatomical details. The soft, skinlike portion of each
valve has an outer and an inner layer of cells which apparently secrete
the hard parts. The distribution of these cells is disturbed only by excre-
tory gland B, the liver, and the ovary which all lie within this epidermis.

The cells which form the two layers in the epidermis may be referred

62 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

0 10u
[cere

subdermol cell

pigment body

chitin lining of epidermis

supporting fibers

nerve cell

axial filament

epidermal cell of inner layer

middle cell
accessory cell
inner margin

list

epidermal cell
of outer layer

scolopoide body

terminal filament

distal cell bulbous base

of hair

selvage
flange

radial pore canal duplicature

normal pore canal

chitin coating of epidermis

chitin coating of calcareous layer

Fig. 32. Diagrammatic section through the anterior ventral part of the right
valve as seen from the front.

to as epidermal cells. These are the Hypodermiszellen of Claus (1898,
pp. 19-20). By function they are the epithelial type of cells, as Rome
stated. The two layers are not similar in the case of Cypridopsis vidua.
The outer layer is composed of subangular cells approximately 10p in
diameter. Each cell is distinct (Plate 1, No. 4; Plate 2, No. 7). The cells
of the inner layer, on the other hand, are flat and form a more regular
continuous layer. They are closely joined to the chitin lining of the
epidermis (Fig. 32).

DETAILED DESCRIPTION 63

The two layers of epidermal cells are not in contact, but have a space
between them. This space is transversed by numerous supporting fibers,
which act as reinforcing girders from the chitin lining to the chitin coat-
ing of the epidermis (Plate 2, Nos. 5-8). These supporting fibers divide
the space between the layers of epidermal cells into lacunae.

Lying free in the lacunae are large angular swbdermal cells, which are
also found in the hypostome and the upper lip. There are very few of
these cells in the epidermis of Cypridopsis vidua. The subdermal cells
are not attached at any point of their boundaries (Plate 2, No. 6).
Various earlier descriptions of the subdermal cells were made, but Claus
(1893, pp. 19-20) was the first to give an accurate account which left no
confusion between the subdermal and the epidermal cells. Rome (1947,
p. 68) claimed to have observed movement of the subdermal cells in the
epidermis.

The epidermal and subdermal cells can be distinguished from each
other by several characteristics. The subdermal cells lie free in all cases;
but the epidermal cells are fixed in place, normally by transverse sup-
porting fibers passing through the middle part of the cell, and in the
region of the ovary, liver, and excretory gland B by trabecular fibers
parallel to the surface of the epidermis. The epidermal cells in the
“striped” areas of the shell have numerous small black bodies of pigment
enclosed in their protoplasm, giving the dark color; there are no pig-
ment bodies in the subdermal cells. The epidermal cells also have smaller
nuclei than the subdermal cells (Fig. 32).

The function of the subdermal cells has never been established defi-
nitely. Claus (1893, p. 20) made the logical suggestion that they serve the
function of blood cells. Yet no explanation of their circulation has been
offered; and the means by which they could eliminate waste products
and carry oxygen to the tissues poses an even greater problem.

In addition to its function of secreting the hard parts of the valve, the
epidermis is equipped with many “hairs” (actually little setae), sensi-
tive to touch, which project through pores in the hard parts and serve
to warn the animal when the shell nears contact with outside objects.
Each hair is actually a projection of the chitin coating of the epidermis.
The hair has a bulbous base, and the perforation through the calcareous
and chitinous layers forms a spherical cavity, concentric to the base of
the hair. In many cases the chitin coating of the epidermis is indented
before turning outward to form the base of the hair. In extreme cases the
depth of this invagination reaches 8u (Plate 52, No. 247; Plate 53, No.
248). The sensitivity of the hair is due to a complex arrangement called
a scolopoide by Rome (1947, p. 72), similar to that found in insects.
Scolopoides are found also in connection with the setae of the various
appendages. Each of these innervating processes extends from the base

64 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

of the hair (or seta) to a basal nerve cell, and consists of: a distal cell,
terminal filament, accessory cell, scolopoide body, middle cell, and axial
filament. The terminal filament has its distal end lying free in the base
of the hair and its proximal end attached to a scolopoide body in the dis-
tal end of the middle cell. The scolopoide body is a narrow cone of sensi-
tive fibers, with its apex directed outward and joined to the terminal
filament. The axial filament extends from the nerve cell into the middle
cell, where its distal end lies free within the cone-shaped scolopoide body.
Any displacement of the hair brings its base in contact with the terminal
filament, which then moves the scolopoide body on its other end; this
brings the sensory filaments in the cone of the scolopoide body in con-
tact with the axial filament which carries the impulse to the nerve cell.
The distal cell is attached to the base of the hair and to the terminal
filament; it is a specialized epidermal cell and lies in the outer layer of
epidermal cells. The distal cell is large, like the other epidermal cells.
The accessory cell is small, and is attached to the proximal half of the
terminal filament by a cycoplasmic extension. It does not appear to have
any direct control in the functioning of the scolopoide. The middle cell
has a distinet cell wall, and has a large vacuole in the distal end where
the scolopoide body is located. It is pear-shaped, with the protoplasm
more or less restricted to the rounded proximal end.

Most of the hairs extend through normal pore canals, but there are
some which are found along the junction of the outer lamella and the
duplicature, reaching through radial pore canals. The radial pore canals
are quite narrow except for a conical enlargement near the end (Fig. 32).
The conical base of the hair fits into this enlargement, and does not ex-
tend the full length of the pore as in the normal pore canal.

Harp PARTS OF THE VALVES

The epidermis is in contact with a chitin covering over most of its sur-
face; in the central dorsal area it opens on the inside to the body itself.
The covering on the inside wall may be designated as a chitin lining of
the epidermis and on the outside wall as a chitin coating of the epidermis
(Fig. 32). The chitin lining of the epidermis (together with the duplica-
ture) has been referred to as the inner lamella of the shell (Claus 1893,
p. 6; Bradley 1941, p. 8). When used for ostracods, “inner lamella” has an
entirely different meaning from that which it has when used for pelecy-
pods. Confusion has resulted, and there is little to recommend the further
use of the term.

The chitin lining of the epidermis folds back upon itself near the center
of the valve, and is then known as the body wall. There is no change in
composition and no structure to mark the division between the two. It
may be said that the soft tissues of the body are held up in a chitin pouch,

DETAILED DESCRIPTION 65

which is a continuation of the chitin linings of the two surrounding valves.

The calcareous parts of the shell, as stated above, are the outer lamella
and the duplicature. The term ‘outer lamella” has been used by Bradley
(1941, p. 8) to include the calcareous part, the chitin coating of the epi-
dermis, and the chitin coating of the calcareous layer. Again, this is a
question of terminology. In this paper, “outer lamella” and ‘‘duplicature”
are used in reference to calcareous parts only.

The outer lamella and the duplicature are “welded” together at the
anterior, ventral, and posterior borders of the shell by a chitin layer.
This chitin layer joins onto the junction of the chitin lining and the
chitin coating of the epidermis, and is tranversed by the radial pore canals
(Fig. 32). The line along which these three chitin layers come together is
called the line of concrescence by Bradley (1941, p. 9) and Verwach-
sungslinie by Miller (1898, p. 258).

Both the outer lamella and the duplicature have a waxy chitin cover-
ing. The line of contact of the chitin lining of the epidermis and the
chitin coating of the duplicature is the inner margin. It marks the proxi-
mal limit of the duplicature.

The character of the border of the outer lamella, the duplicature, and
their chitin coatings is of specific value in ostracod taxonomy. In Cypri-
dopsis vidua the left valve overlaps the right valve throughout the peri-
meter. However, the valves are nearly the same size, and the overlap is
made by thin projections around the border.

The structures of the border areas are quite complex. Not only do the
structures of one valve differ from those directly opposite in the other
valve, but structures change radically from one point to another around
the perimeter of each valve. The closure is accomplished in the simplest
instances by razor-like projecting ridges of the duplicatures, called the
selvages by Bradley (1941, p. 10), which overlap and produce a seal
along their contact areas. The selvage is the Sawm of Miller (1898, p.
258) and later German workers. The selvage varies from a low, blunt
ridge to an elongate delicate structure, and in some cases is curved out-
ward (Fig. 32). In some sections the selvage is paralleled by an outer
ridge, the flange, and/or an inner ridge, the list (Leiste of Muller). The
flange may be developed at the welded area as a structure shared by the
outer lamella and the duplicature, or it may be confined to the outer
lamella alone. The flange does not always form the outer margin of the
shell, and sometimes occurs as a small ridge on the outside of the shell
when the selvage is unusually well developed and forms the outer margin.
The flange is separated from the selvage by a portion of the shell called
the flange strip. This may form a groove, which is known as the flange
groove. The list is usually not as well developed as the selvage. The part
of the duplicature lying between the selvage and the list is the selvage

66 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

strip, and when this forms a groove, that is called the selvage groove.
The part of the duplicature between the list and the inner margin is the
list strip.

The space enclosed between the outer lamella and the duplheature is
termed the vestibule by Bradley (1941, p. 8). In living specimens, this
space is occupied by the distal portion of the epidermis. In fossil species
having only the caleareous parts of the shell preserved, the term ‘‘vesti-
bule” has more significance.

Although the Cypridae are said to have no teeth, there are in Cypri-
dopsis vidua along the median dorsal border several interlocking small
corrugations which serve the function and have the form of ‘“micro-
teeth.” In the right valve these are found on a flat vertical surface out-
side the selvage (Fig. 7; Plate 66, No. 291). The corresponding ‘“micro-
teeth” in the left valve are on the thickened edge of the selvage.

Immediately posterior to this toothed area the selvage of the left
valve occurs in the middle of the marginal face and turns up sharply.
It fits very intimately into a deep incurved flange groove of the right
valve (Fig. 7; ef. Gauthier 1939, Fig. 6D). This evidently functions much
the same as the pseudocardinal tooth arrangement in schizodont pele-
cypods.

The posterior region has an unusually well developed duplicature which
extends beyond the line of concrescence to form a large vestibule space.
The right valve has a flange, selvage, and a small rounded ridge corres-
ponding to the lst. The list hes next to the inner margin. The left has a
selvage extending outside the flange of the right valve, a wide selvage
strip, and a weakly developed list next to the inner margin. Thus, in this
region the selvages of the two valves lie widely separated.

In the center of the ventral border, both valves have only thin, very
wide selvages, which he almost horizontal. The lip-like selvage of the
left valve completely overlaps that of the right when the shell is closed.
Tips of both selvages are turned outward.

In the anteroventral region the selvage of the right valve is turned
strongly outward (downward) and there is development of the flange and
the list (Fig. 32). In the left valve the selvage projects forward at an
angle to fit against the flange of the right valve. There is a slight develop-
ment of a flange in the left valve, but it has no connection with the closure.
As seen from the side, the line of concrescence in the right valve hes
between the flange and the selvage, while in the left valve it les to the
inside of the selvage.

In the anterior end there is some question as to the limits of the inner
margin. By definition, the inner margin marks the proximal extent of
the duplicature. When a valve of Cypridopsis vidua is broken and the
anterior end is tilted under double polarized light, the calcareous portion

DETAILED DESCRIPTION 67

of the duplicature appears to be limited to about 40y in width. There is
a pattern of interlacing grooves on the thickened chitin in the anterior
region. This grooved area is sharply set off proximally by a curved line
(Fig. 7). It seems that the chitin lining of the epidermis and the chitin
covering of the duplicature continue in contact with each other beyond
the inner limit of the caleareous duplicature to form the grooved area.
The grooves do not show any significant structure, and they seem to be
functionless. The right valve has a selvage turned strongly outward and
a small marginal flange. In addition, the right valve also has a row of
about fifteen tubercles on the outer lamella near the margin. These vary
both in size and in number in individuals of the same clone. The left
valve has no tubercles, and the selvage embraces the flange of the right
valve in a well-developed overlap. The flange of the left valve is a low,
rounded rim which does not enter into the closure.

Very little has been written about the structure of the calcium carbo-
nate in the shell. Dudich (1929, p. 257) set up a classification of the
crustacean shell as follows:

I. Achalicodermal: lacking a calcareous layer.

II. Chalicodermal: calcareous layer present.

1. Amorphochalicose: calcareous material amorphous.
2. Morphochalicose or crystallichalicose: calcareous material crystalline.

According to this classification, the ostracod shell is chalicodermal, since
it contains calcium carbonate. It is further morphochalicose, because the
calcium carbonate is crystalline. Under double polarized light, the ostra-
cod shell shows extincition parallel to the orientation of the nicols, with
illumination of the rest of the shell (Plate 67, Nos. 293-296). This shows
the mineral of the shell to be anisotropic. The same results are obtained
when the shell is tilted and when it is viewed from the dorsal edge. There-
fore, the mineral is cryptocrystalline, with some (if not all) of the crys-
tals at right angles to the surface of the shell.

X-RAY DIFFRACTION STUDY OF THE OSTRACOD

An X-ray powder pattern was made to determine the nature of the
shell material. Cypridopsis vidua specimens were removed from the
aquarium by means of a pipette to avoid contamination with bottom sedi-
ments. The ostracods were filtered from the sample and allowed to dry
for twelve hours. Several hundred specimens were then packed into an
acetate tube about 1 mm. in diameter. The X-ray machine was the cop-
per-target type, and was used with a nickel filter. The tube containing the
ostracods was mounted in a collet in the center of a circular metal camera
14 cm. in diameter, and rotated throughout the exposure by a small
motor. An exposure of one hour forty-five minutes was found to give
good results.

68 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

D Measurements from an X-ray Powder Pattern Photograph of Ostracods, Compared
with the D Measurements of Calcite and Quartz.

OsTRACODS Ca.crtTe! CALCITE” ALPHA-QUARTZ
Angstrom Inten- Angstrom Inten- Angstrom Inten- Angstrom Inten-
units sity units sity units sity units sity
4.495 vt Fae age ae sae aay bogs te
4.25 f a6 rons nee are 4.25 0.25
3.867 f 3.877 m zee ae
ae Eio7 ene ame 3.36 m eee cies
3.340 st A? nie or aa: 3.35 1.00
3.205 vi ae ae ae ror. aah seis
3.020 vst 3.04 1.00 3.03 vst we svete
2.851 vi : eee a. me Bre
nee 2.80 f ae Bes
2.700 vi LEN : oe ape
2.576 vi nn set one os Fb wae
2.478 m 2.49 0.20 2.495 m bate nes)
ne ae ae ay: a ick ee 2.45 0.15
2.276 m 2.28 0.24 2.308 m 2.29 0.10

Me : 2.23 0.06
ree eas ab rene ear 2.12 0.09
2.084 m 2.09 0.20 2.102 m - ea
1.987 vi eer aioe: 1.997 vf sue
ea: Se see 1.97 0.08
1.928-\
1.921 | m 1.92 0.32 1.912 st
1.905 m ee ee ‘ moe
1.88 m 1.87 0.24 - eS ean
1.826 f save ~ Ae 1.82 0.25
oA Be ar 1.82 0.25
; a 1.79 vi se
x eee 1.689 vi ie
1.671 vi es ws 1.66 0.08
1.602 m 1.60 0.16 1.615 m a.
te “or oe Saf 1.54 0.20
1.524 m 1.51 0.12 1.524 m : ne
1.48 vi 1.475 0.05 1.479 vf by: ius!
oe : sachs Nae —_ 1.450 0.02
1.488 f 1.489 0.08 1.485 m : ant
1.417 f 1.425 0.05 un fed
1.378 vi Set ae 1.375 0.25
1.360 vi 1.35 0.03 1.36 vi : sete
1.339 vi - ae ne ue aie
1.295 vi 1.295 0.05 1.296 f 1.299 0.04
ae oe ae 1.256 0.03
1.250 vi 1.243 0.03 1.241 f ae alee
233 vi ff sae: ; ae ane
sd - ; 1.228 0.03
1.201 vi . aes - 1.200 0.06
1.181 f 1.179 0.03 1.185 m 1.180 0.08
1.155 m 1.15 0.05 1.156 m 1.155 0.01
1.145 vt _ od 3 — ne
. 1.124 vi Af 2
or 1.080 0.04
1.064 vi 1.063 vi eh Ee
047 m 1.045 0.06 1.047 m 1.048 0.02
1.038 f 1.040? vi ad a
oe Aa. ae Aoi ae aad 1.035 0.01
1.011 f 1.014 a 1.014 vi 1.015 0.01
0.990 vi 0.987 f oe as
0.978 vi ee nae
0.964 f 0.967 f

DETAILED DESCRIPTION 69

D Measurements from an X-ray Powder Pattern Photograph of Ostracods, Compared
with the D Measurements of Calcite and Quartz.

OsTRACODS Ca.ciTe! CALCITE? ALPHA-QUARTZ
Angstrom Inten- Angstrom Inten- Angstrom Inten- Angstrom Inten-
units sity units sity units sity units sity

0.944 f 0.944 m

ae ee 0.925 vi
0.902 m
0.891 m
0.875 if
0.863 m
0.854 f
0.843 m

Key: vst— very strong; st—strong; m—medium; f—faint; vf— very faint.

4The figures in the first column for calcite and for alpha-quartz were taken from the file
cards in the chemistry department, University of Illinois.

2The d measurements for calcite listed in the second column were computed from the s distances
given by Heide (1924), according to the formula

-_ 7.68
~~ sin (0.714 s).

This formula is based on the average conversion factors required to derive the strong intensity
lines of calcite, aragonite, and mu-CaCO, as given by Heide.

The computed d distances are given in Angstrom units.

The X-ray analysis shows calcite and alpha-quartz present. There is
no indication of either aragonite or mu-CaCO, (vaterite B of Gibson,
Wyckoff, and Merwin, 1925, p. 331). The intensity of the lines corres-
ponding to calcite on the film indicates that there was a considerable
quantity present in the ostracod sample. The alpha-quartz may all be
attributed to the siliceous skeletons of diatoms present in the stomachs
of the ostracods.

It will be noted that there are some additional lines which do not cor-
respond to either calcite or quartz. These may possibly be lines from
organic remains of the ostracod, from the chitin, or from some mineralogic
contamination. The preparation of the original sample excluded any ap-
preciable quantity of impurities, and it is not known whether or not the
ostracod eats quantities of clay and other minerals with its food.

The lines with the greatest d values may be indications of organic
remains of some type. The clarity of the lines indicates the crystalline
nature of the material. The lines do not appear to come from chitin.
Clark and Smith (1936, p. 875) show powder patterns of chitin from the
lobster Homarus americanus to be very diffused, indicating an almost
amorphous structure. Chemically, chitin is identical with cellulose except
that the secondary hydroxyl on the alpha carbon atom of the latter is
substituted by an acetamide group. Chitosan is closely related to chitin.
The formulas given here are those given by Clark and Smith (1936, p.
864). There is no evidence at the present time that the substances of
crustacean shells called chitin by the zoologists are identical with the

70 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

prepared substances called chitin by the chemists. Clark and Smith
(1936, p. 864) found that lobster shell material treated with dilute nitric
acid, heated for four hours with 20 per cent NaOH, bleached with per-
manganate and bisulphite, and finally dehydrated with aleohol and
ether, produced a chitin nitrate, which was crystalline, probably orthor-

Cellulose Chitin Chitosan
|
| | |
O O oO
| | |
| 1
*€ C C
H x aa H ae ve H aN
. ~~ Va \. HO Bro
oO HCOH O HCNCCH; O HCNH
| | | | |
HOH.CCH HCOH HOH.CCH HCOH HOH.CCH HCOH
~ F N y \
\ \ Ye Ss vA
NOW 7 oy H hi I H va
Cc C Cc
| | |
O O O
| | |
c Cc c
fu CTS Ve aN
yA < OH << OH / Xe
HOCH O CH3CNCH O CH;CNCH O
| | | | | |
HOCH HCCH,OH HOCH HCCH.OH HOCH HCCH,0H
‘ G % J ~ we
Sy ay Se
c C C
| | |
O oO O
| | |

hombic. Chitosan was also prepared from lobster chitin by the action of
fused KOH at 180° C., and was found to produce orthorhombic crystals.
Meyer and Pankow (1935, p. 590) prepared chitin from the tendons of.
Palinurus vulgaris by treating it with caustic soda, hydrochloric acid,
and finally extraction by alcohol. They were then able to obtain definite
lines on an X-ray powder pattern of the substance. Again, the crystal-
line substance from which the powder pattern was made was not in its
natural biological occurrence.

The writer made an X-ray powder pattern of dried Daphnia longis-
pina, since these cladocerans do not have any calcium carbonate in their
shells, which are said to be made entirely of chitin. The film showed only
very diffuse halos of high d values (approximate values of 4.5 and 11.7
at the center of the diffuse bands). These match diffuse halos on the

DETAILED DESCRIPTION 71

powder photograph of the ostracods, but the lack of definition excludes
the conclusion that they are both caused by chitin.

SECRETION OF THE SHELL

There do not appear to be any special cells which secrete the shell
material. It seems to be formed by all of the epidermal cells. Furthermore,
there is no apparent difference between those epidermal cells of the imner
layer which secrete only chitin and those which secrete the duplcature.
The whole process of shell secretion in the ostracod is entirely different
from that in the pelecypod. The pelecypod adds material continuously as
the mantle grows; and although the growth is rapid during the summer
and inhibited during the winter months, it cannot be said to be discon-
tinuous. The ostracod, by contrast, sheds the entire shell with each molt-
ing and secretes a new one, of different size and shape. The actual process
of shell formation may show rhythmic activity, as Zschorn (1937, pp.
323-48) found to be the case for other arthropods.

No one has investigated the biochemical conditions which initiate the
molting process and those which stimulate the sudden precipitation of
chitin and calcium carbonate for the new shell. Fassbinder (1912, pp.
556-57) established that the immediate source of the calcium carbonate
was from the body of the ostracod and not from the water. On April 26
he isolated seven instars, including those of Cypris pubera, Cypris virens,
and Cypris fuscata. All were placed in calcium-free water and fed on
sphagnum moss, which is acid and noncaleareous. The old shells were
removed after each animal molted to insure that there was no outside
source of calcium carbonate. The first animal molted on April 27 and
the sixth on the morning of May 2; the seventh animal did not molt. On
the evening of May 2 all the specimens were killed, and were found to
have hard shells. The calcium carbonate for the shell material must have
been stored up by the sixth animal at least five days previous to the
molting.

How the calcium carbonate is obtained and stored up by the animal
has been studied very little for the ostracod. However, the important
work of Mann and Pieplow (1938, pp. 1-17) on the calcium carbonate
changes in the crayfish during molting may have some bearing on the
problem of the ostracod. They found that prior to the molting, the total
weight of the crayfish shell is reduced to only one-fourth its normal value,
with a proportionate decrease in its calcium content. The progressive
decrease in the weight of the shell is accompanied by the appearance and
growth of gastroliths in the stomach of the crayfish. These gastroliths
contain calcium, but not in sufficient quantities to make up for all of the
decrease in the shell. They then analyzed the ecaleium content of the
blood during the molting process and found it to be 150 per cent of its

be THE MORPHOLOGY OF OSTRACOD MOLT STAGES

normal value. After the molting process the gastroliths decrease and dis-
appear as the shell increases in weight and proportionate calcium content.
However, the gastroliths are evidently not a source of the calcium for
the new shell, since (1) the calcium content of the shell after the gastro-
liths are lost is approximately three times the calcium content of the ori-
ginal gastroliths, and (2) the rate of calcium increase in the new shell
is the same before the disappearance of the gastroliths as it is after. If
the gastroliths contributed to the shell, there should be a rapid rate of
addition part passu with the diminution of the stones. The mechanical
abrasion of grinding in the stomach is cited as an explanation of the de-
pletion and disappearance of the gastroliths. Mann and Pieplow then
conducted feeding experiments on newly molted crayfish to determine the
source of the calcium. One group was placed in normal tap water and
left without food for twenty-one days. The shell was paper-like and elas-
tic. The animals were then fed on Chara, rich in calcium, for an additional
twenty-six days. The shells were unchanged. A second group of crayfish
was placed in soft water and fed on Chara; at the end of thirty-two days
the shells were little hardened and still elastic. The third group were
placed in flowing hard water without food; at the end of thirty-two days
the shells were completely hardened. The crayfish, Mann and Pieplow
concluded, derive the calcium for the new shell from external sources and
specifically from a large quantity of hard water. It was also found that
feeding with the flesh of other crayfish, rich in calcium, failed to produce
calcium increase in molted animals. These investigations show an entirely
different situation in the case of the crayfish from that reported for the
ostracod. Fassbinder’s experiment, showing that the ostracod ean store
calcium for the shell before the molting takes place, has already been
discussed. It is possible that the phylogenies of the crayfish and the ostra-
cod have produced not only morphological differences, but also differ-
ences in their biochemical processes.

There is apparently another difference between the crayfish and the
ostracod in regard to calcium assimilation. Experiments have shown that
the diet affects the weight and shape of the ostracod shell. Fassbinder
(1912, p. 563) set up two cultures of Cypris pubera O. F. Miller, a
normally smooth shelled form. One culture was fed on a diet of crushed
snails, rich in calcium. Animals in this culture developed a secondary
thickening of the shells, marked by conspicuous anterior and posterior
protuberances. Animals in the second culture were fed on a plant diet
and maintained the typical smooth form. Unless the history of the indi-
viduals had been known, most certainly those on the caleium-rich diet
would have been classified as a distinct species.

Wohlgemuth (1914, p. 21) conducted a converse experiment with Cy-
prinotus meongruens Ramdohr. Animals were fed on a near-starvation

DETAILED DESCRIPTION vie

diet, and developed saddle-shaped indentations in the posterior dorsal
border. Others in a control culture were of the normal shape.

Any ecological study of ostracods should include the food supply as a
possible cause of exotic shell shapes occurring within a given species.

THE CLosiInc MUSCLES

The muscles which serve to close the two valves have been referred to
as the closing muscles (Schliessmuskeln, Vavra 1891, p. 11; Claus 1893,
p. 14), adductors (Sharpe 1918, p. 790; Hoff 1942, p. 42), and occlusor
muscles (G. H. Fowler 1909, p. 221). Muscles from the two valves are
joined in the center of the body to a short, chitinous rod. The distal ends of
the muscles are attached to the chitin coating of the epidermis, which is
in turn fastened to the calcareous layer. There is no evidence that the
muscle fibers penetrate into the calcareous layer.

The muscle fibers, which are striated, change their character as they
enter the epidermis layer. The fibers diverge to cover a larger area, and
are no longer striated. The distal tips of the individual fibers appear to
be enlarged where they join onto the chitin layer. Where the closing mus-
cles penetrate through it, the epidermis hes in contact with the chitin
layer (Plate 3, No. 9; Plate 22, No. 145; Plate 23, No. 146). The epider-
mis in these areas is composed of very finely granular protoplasm, and
has no epidermal cell nuclei. The chitin in contact with the ends of the
fibers from each muscle appears to differ from that in the remainder of
the valve; in Cypridopsis vidua there is a secondary deposit of chitin in
the form of a low flat boss, to which the fibers are attached. There is one
boss for each muscle. These bosses are clearly set off from the rest of the
chitin layer by distinct lines of demarcation.

It is very difficult in the whole valve to tell whether the bosses are
present or not, for they have very little relief, and are apparently com-
posed of the same material as the rest of the chitin. It is the writer’s
opinion that the bosses are so firmly welded to the chitin coating of the
epidermis that they are molted with the other hard parts of the valves.
This means that these areas are of special significance in the formation of
the new shell. The chitin coating of the epidermis is apparently secreted
after the calcareous layer, since it separates the CaCO, deposits from
the epidermis which must have secreted them. Then the epidermis at the
ends of the muscle fibers must have a supplementary secretion of chitin
to fasten the muscles to the hard parts of the shell.

The muscle scars found on fossil ostracods are of different types as
well as designs. As seen from the inside surface of the valve, some are
raised areas, some are depressions, and some have many small pits. A
complete study of all living species might throw some light on the original
differences in muscle attachment. However, it should also be considered

74 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

that the differences may arise in part from selective replacement in the
fossil forms. If the thin boss and a part of the epidermis attached to it
were preserved, then the fossil form would have a strongly raised process
marking the former position of the muscle; but if the rest of the epidermis
were replaced and the portion with the muscle fibers were lost (by decay),
then the fossil would have only depressions as muscle scars. If the muscle
fibers penetrated through the epidermis in large bundles, then the muscle
scar could bear many pits. Since muscle scars are used in the taxonomy
of fossil forms, they deserve special study. Actually, very little is known
about them at the present time.

RESPIRATION

The ostracod has no special structure for obtaining oxygen from the
water in which it lives. Many writers have suggested that respiration is
carried on by absorption through the epithelium, which includes the body
wall and the lining of the epidermis of the shell (Edwards 1857, p. 118;
Claus 1895, p. 28; Bernecker 1909, pp. 583-630; Blochmann 1915, p. 391;
and others).

Even preliminary observations of ostracods show that they require
oxygen for life. They do not occur in waters which are oxygen-deficient.

At the present time morphological studies have neither confirmed the
respiratory role of the epithelium nor cast any doubt upon it. The exo-
podite plates of the maxillae are sometimes referred to as the respiratory
plates because they serve to circulate a fresh supply of water in the space
within the shell. They are in constant motion. There are no special res-
piratory structures in the plates themselves.

REPRODUCTIVE SYSTEM

Cypridopsis vidua is a parthenogenetic species, apparently at all times,
despite the statement by Weismann (1880, p. 83) that this species is
only temporarily parthenogenetic, and the report of a male by Spandl
(1925, p. 118). The latter is seriously questioned by Khe (1938a, p. 132).
The writer has maintained a culture through a period of two years, has
examined adult individuals at intervals throughout that period, and has
never seen a male.

The reproductive system of C. vidua contains the same parts as that
found in syngamic species, with no reductions whatsoever.

It must be made clear at the beginning that there are two distinct por-
tions of the system: the first is the circuit followed by the egg, and in-
cludes the ovaries and uteri; the second part is normally used in the
reception and storage of sperm, and includes the vaginas, the ‘copulation
bladders,” the spiral canals, and seminal receptacles. The left half of
the system is a mirror image of the right half, but the two are not con-
nected in any portion.

DETAILED DESCRIPTION 75

The ovaries originate in the hypodermis layer of the valves in the
posterior part of the animal. Each curves backward and downward,
forming approximately two-thirds of a circle, then extends forward and
upward parallel to the liver (Fig. 1). It then passes into the body, where
it is known as the uterus or egg tube.

The ovary of the ostracod offers an unusual opportunity for the study
of odgenesis, for the time of development of an egg cell can be estimated
from its position in the ovary. The first few microns of the ovary forms
a syncytium where the eggs originate. The various stages in partheno-
genetic development of ostracod eggs was first adequately described by
Woltereck (1898, pp. 602-8), who worked with Herpetocypris reptans
Baird and Cyprinotus incongruens Ramdohr. He distinguished two major
zones of development: the germinal zone, where the eggs originate, and
the growth zone, where the many changes in the eggs occur. The growth
zone is divided into three parts: (1) the synapsis zone, in which the
chromosomes are isolated at one side of the cell, (2) a “differentiation”
zone, in which the egg cells become distinguishable from the nurse cells,
and (3) the growth zone (restricted sense), in which the yolk is added
to the egg and further developmental changes take place in the egg and
nurse cells. The odcytes produced in the germinal zone pass through a
stage of synizesis (called simply “synapsis” by Woltereck) exactly the
same as that in the sexual egg (Wilson 1925, p. 793). Weismann and Iski-
kawa (1888, p. 21) state that the parthenogenetic development is diploid,
and only one polocyte is present. It is typical of the whole animal king-
dom that female-producing eggs always develop with the diploid number
of chromosomes. The developing egg increases its yolk content from two
sources: the first is from the yolk nuclei or vitelline bodies within the
cell; and the second is from separate nurse cells, whose nutritive sub-
stances are sacrified to the egg. These nurse cells develop with the same
synizesis as the true egg cells; indeed, Claus (1893, p. 21) believed them
to be abortive eggs, whose destiny it was to supply vitelline content to
the functional egg cells which had followed the same path with more
success. The nurse cells are exhausted in their progress through the ovary,
and they do not appear in the uterus.

The ovary turns into the body and becomes the uterus without con-
spicuous change. The actual opening or passageway from one to the
other hes posterior to the duct from the liver to the stomach (Plate 36,
No. 215). The uterus has a normal diameter of about 304, but can be
distended to 100» to pass the eggs. The outside wall of the uterus has a
well-defined boundary; the inner wall (bounding the lumen) is irregular
(Plate 37, No. 216). There are two sections of the uterus, not sharply
separated, based on the wall structure. The initial part is made up of
large cells with very finely granular protoplasm and some trabecular
tissue, giving it a spongy appearance (Plate 36, No. 214). In contrast,

76 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

the remainder of the duct contains large glandular cells (Plate 36, No.
215). The use of these cells is still only conjectured. The most logical
use of the cells in the posterior part of the uterus is to secrete the double-
walled shell of the egg (Miller 1894, p. 150: “Der scharf abgesetzte
glockenférmige Endabaschnitt ist von einem hohen Cylinderepithel aus-
gekleidet. Er diirfte sowohl als Befruchtungsraum dienen als auch eine
Eihiille liefern.’”’). The egg shell is complete upon leaving the animal.
Another suggested use of the cells is to furnish a secretion for formation of
the threads used to anchor the eggs (Woltereck 1898, p. 601: “Die Faden
und ihre urspriingliche Dehnbarkeit beobachtet man unter dem Mikro-
skop. — Das Spinnsekret wird, nach einer schriftlichen Mittheilung, die
ich der Giite des Herrn Hofrath Claus verdanke, wahrscheinlich von
einer Driise am Ausgang des Oviducts geliefert.’”’). It seems quite possible
that both of these functions may be performed by the glandular section.
The opening of the uterus is on the inner face of the genital lobe (Plate
40, No. 222). It is narrow and much elongated, difficult to see unless it is
distended by an egg in the end portion of the tube.

The rigid framework of the vagina has been discussed with the genital
lobe. It leads to the spiral canal, which terminates in the seminal recep-
tacle. There is some disagreement as to the nature of the connection of
the vaginal opening and the spiral canal. Bergold (1910, p. 28) reported
that the vaginal opening led to a large copulation bladder, situated above
the chitin framework, which tapered at the anterior end into the spiral
canal. Fassbinder (1912, p. 567) did not believe in this arrangement, and
described the connection as simply horn-shaped, with the smaller end
connected to the spiral canal. The writer has found an intermediate con-
dition in Cypridopsis vidua, where there is an enlarged tubular section
curving forward and upward to the more rigid spiral canal (Plate 39,
No. 221; Plate 49, No. 240). This tubular section is lined with glandular-
type cells, and lies to the inside of gland O, which it resembles very
much. It is here called “copulation bladder,” to correspond to Bergold’s
designation. The “copulation bladder” does not seem to be appropriately
named: apparently it does not function as a collecting place, or bladder,
but is actually the vagina. Unfortunately, this latter term has been ap-
plied to the chitin framework of the opening.

Gland O, the “copulation gland” of Bergold (1910, p. 28), has already
been described. It empties near the opening by a narrow duct.

The spiral canal is unusually well developed, even though the species
is parthenogenetic. From its junction with the “copulation bladder” it
passes to the outside of the genital region and forms a tightly wound
ball before ending at the posterior end of the seminal receptacle (Plate
53, No. 248). The canal is remarkably uniform throughout its length,
about 6» outside diameter and 4p inside diameter (Plate 40, No. 222).

DETAILED DESCRIPTION er

The total length is over 850u, but it is wound into a mass only 60, in
diameter.

The seminal receptacle, which in this species never contains any
sperms, is an elongate tube lying horizontal in the posterior part of the
animal (Plate 38, No. 219). It is connected with the spiral canal at the
rear. It is filled with a clear fluid substance, which might (in syngamic
species) serve as nourishment for the sperms until they are used. The
anterior blind end of the receptacle terminates in an unturned nipple-
shaped structure (Plate 48, No. 238). This structure may be the Pol
which was described by Zenker (1854, p. 48) as being opposite the en-
trance opening, and which Bergold (1910, p. 34) was unable to find.

There is another phase of the female genital system which is a subject
of disagreement, and which applies to the syngamic species directly.
A great deal has been written about how the sperm get into the seminal
receptacle, but very little about how they get from the receptacle to the
uterus, where the eggs are fertilized. Only one opening of the receptacle
has been found, and that opens into the spiral canal; thus the entrance
is also the exit for the sperms. Klie (1926, p. 37) and others have stated
that the spiral canal leads into the end section of the uterus, apparently
beheving that the vaginal and the uterine openings are one and the
same. The writer has seen no internal connection between the vagina
and the uterus. Bergold (1910, p. 35) offered a logical solution to the
problem, suggesting that the sperm travel out of the vaginal opening and
into the uterine opening when the two are in contact. The muscles
attached to the chitin “stick” pull the upper part of the vaginal frame-
work downward, turning the structure so that the opening faces directly
to the rear. This action brings the vaginal opening closer to the uterine
opening, and additional contraction of the muscles may bring the two
in contact. There is also a broad band of muscles connecting the anterior
and posterior ends of the genital lobe, which by contraction would move
the two openings closer together (Plate 49, No. 241). This explanation of
how the sperm travel from the storage space (seminal receptacle) to the
fertilization room (rear section of the uterus) fits the observed morpho-
logical facts very well.

It has been definitely established that one species Cyprinotus incon-
gruens Ramdohr, may reproduce either by parthenogenesis or by syn-
gamy. Reports of this species in nature shows that males and females
have been found in central Germany, Hungary, and North Africa, but
only females are reported in western and northern Europe and central
United States. This geographic distribution of parthenogenetic and syn-
gamic races of the species cannot be explained on the basis of climate,
food supply, or size of the bodies of water. There is no morphologic
difference between the two reproductive types.

78 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

Experiments carried out by Wohlgemuth (1914, pp. 57-63) show that
the parthogenetic condition may be induced in cultures. With all males
removed, the females reproduced parthenogenetically. All of the young
were females, and neither males nor spermatozoa were found on examina-
tion of the animals. Parthenogenesis was not a result of the isolation of
a syngamically produced female, for the cultures continued to reproduce
with no males. The ostracods from which the cultures were started con-
tinued to be syngamic.

Wohlgemuth (1914, pp. 62-63) was able to reverse the experiment,
producing a syngamic form from a parthenogenetic, in only one case.
An originally syngamic form of Cyprinotus incongruens was changed to
the parthenogenetic form by isolation of the females as above. Then
females from this race were fed on excrement and brown algal residue
and returned to the syngamic condition. These cultures were maintained
on a minimal diet of potato peelings and continued to reproduce male and
female offspring by syngamy. Four separate cases of changes from par-
thenogenetic to syngamic races in nature have been observed by Wohlge-
muth (1914, p. 65) with no seasonal return to parthenogenesis.

The exact role of the sperm in syngamic reproduction of ostracods is at
present only conjecture. After a study of the structure and motility of
ostracod sperm, Lowndes (1935, pp. 35-48) concluded that the sperms
were nonfunctional, and that copulation has continued in the ostracods
after its fertilizing function was lost. If copulation is an instinctive vesti-
gial habit without reproductive significance, there still remains the prob-
lem of why impregnated females produce young of both sexes, while
those which remain virgin produce only female young.

IV. Biology

The descriptions of life processes in this section are based primarily on
observations of Cypridopsis vidua. There are some important ecological
relationships which are not represented in the life history of this species,
and these are also included in this paper and credited to the proper
species. This is done to give a full picture of ostracod biology and rela-
tionships.

THE Ecc AND EMBRYONIC DEVELOPMENT

The eggs of Cypridopsis vidua are green in color. Each egg is nearly
spherical in shape, approximately 105 in diameter. It has a double-
walled cover of chitin impregnated with calcium carbonate. The inner
wall is concentric to the outer, separated from it about 5y all around.
The inner wall is held in place by numerous small chitin processes con-
necting to the outer wall.

The embryonic development of the egg has been studied for Herpeto-
cypris reptans Baird and Cyprinotus incongruens Ramdohr by Woltereck
(1898, pp. 609-23), for Cypris ovum Jurine (= Cyclocypris laevis O. F.
Miller) and Notodromas monacha (O. F. Miller) by Schlep (1909, pp.
390-431), and for Cyprinotus incongrwens Ramdohr by Miller-Calé
(19138, pp. 113-70). The results of their investigations show that the
cleavage is total and equal. The first two divisions are meridional, and
the next five are alternately latitudinal and meridional, resulting in a
128-celled blastosphere. Differentiation of the cells into entoderm and
ectoderm begins after the eighth division. The writer has not sectioned
any eggs of Cypridopsis vidua, and the very minute pits on the surface
of the egg shell make observation of the contents impossible.

The rate of development of ostracod eggs has a phenomenal range,
depending primarily upon the desiccation to which the eggs are sub-
jected. Sharpe (1917, p. 797) tells of an instance of samples of dried mud
being sent to England from Jerusalem and Cypris being raised therefrom
after a lapse of from twenty-four to thirty years. Sars frequently de-
scribed faunas which were raised by him in Norway from dried mud
samples shipped from distant lands, including South Africa (1895, pp.
1-56), Australia (1889, 1896), and South America (1901).

This ability to withstand desiccation is attributed by Wohlgemuth
(1914, p. 37) to the presence of a watery fluid between the two walls of
the cover. Woltereck (1898) observed that the two walls of the egg lie

[79 ]

80 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

in close contact while the egg is in the uterus, and do not separate until
the egg is expelled. The space between the walls then fills with “water,”
but whether this comes from an external or an internal source is not
clear. The egg also contains a very large amount of yolk material, which
according to Klie (1926, p. 30) may be a factor in sustaining life in the
egg over such unusually long periods.

Wohlgemuth (1914, p. 37) found that eggs of Herpetocypris reptans
would withstand drying of over a year, although this species did not
occur in his collections from ponds which annually dried up. There is
only one type of egg for ostracods, and winter eggs, such as the cladocera
produce under unfavorable conditions, are never found. It seems likely
that the eggs of all ostracod species are able to survive at least short
periods of drying out.

Ostracod eggs also have a great tolerance of cold, and temperature
has an important effect on the rate of development. It has been found by
Wohlgemuth (1914, p. 42) that eggs of Cyprinotus incongruens kept at
a temperature equivalent to that of their natural environment (9-11° C.)
required fifteen days from the time they were laid until they hatched;
other eggs placed at the same time in water kept at room temperature
(17-19° C.) needed only seven days to hatch; and a third group of eggs
placed in an artificially warmed aquarium (28-30° C.) hatched in only
three days.

When the egg hatches, it splits in a smooth plane into two equal halves.
Usually the two hemispheres remain attached together by a small bit of
unbroken chitin of the outer wall, but this is a very delicate connection
and is broken with the slightest disturbance. No studies have been made
to determine whether the position of the break in the egg shell bears any
relation to the orientation of the nauplius inside.

THE Process oF Ecc LAyIne

The eggs of Cypridopsis vidua are laid in the algae lining the bottom
of the aquarium. It would be a very difficult operation indeed to observe
the process in nature, and it can only be assumed that the animal would
choose a similar site in her natural environment.

The operation of the actual laying of the egg is difficult to observe be-
cause of the opacity of the shell. The mother animal stands motionless
in the algae with the valves partially opened at the beginning of the
process. When attempts were made to orient the shell on its back, so that
the procedure could be seen to better advantage, the disturbed female
partially closed the valves and apparently ceased egg laying operations.
It may be that the second and third thoracic legs assist in the removal
of the egg and pass it forward before the ejection from the shell, for
when the egg emerges from between the valves, it comes from the middle

BIOLOGY 81

of the ventral border. This agrees with the observation of Khe (1926,
p. 39) who suggested that the secretion of the gland of the first thoracic
leg (gland N) may play an important role in the egg laying process.

The eggs are laid singly, and not in clusters. Cypridopsis vidua does
not have an enlargement of the uterus to serve as a storage chamber for
the eggs, as does Candona. Of the many females of C. vidua examined
in this study, both by microtome and by needle dissections, the maxi-
mum number of eggs found at any one time in both of the paired uteri
was three. Wohlgemuth (1914, p. 38) reports as many as eight eggs laid
by C. vidua at one time. There are many periods of egg laying, so that
the progeny of any one female are spaced over a long period of time.
This is discussed more fully in a following section on the rate of re-
production.

The place where the female chooses to lay the eggs appears to bear a
relationship to the oxygen content of the water. Wohlgemuth (1914, p.
41) conducted an experiment with three cultures of Cyprinotus incon-
gruens to determine the effects of environment on the site of deposition
of the eggs. He found that in the culture with abundant algae and a sandy
bottom, the eggs were laid on the bottom; in the culture with a few plants
and a sandy bottom, the eggs were deposited under water half way up
the side of the aquarium; but in a culture without plants and a mud bot-
tom, the eggs were laid above the surface of the water.

It is not possibile to say whether this seeking of an oxygen-rich en-
vironment is caused by the extraordinary respiration requirements of the
female during the egg laying process, or by an instinct which nature uses
to insure a favorable environment for the eggs themselves.

THE Process OF MOLTING

The growth of the arthropods is characteristically discontinuous. Un-
hike the pelecypod or the gastropod, which have their soft parts exposed
along one side and can increase their armor by small increments to keep
pace with their body growth, the arthropod is completely encased by a
hard covering which must be broken open and shed each time the animal
adds to its body size. The ostracod is a typical arthropod. Each molting
of the shell introduces an animal differing from that of the previous
stage, not only in size but also in form. The old appendages may change
their form and function, and entire new appendages are added quickly
before the new armor is secreted. Each molting is a very crucial short
interval in the life history of the ostracod.

Relatively nothing is known about the biology of the molting process.
In other words, no one knows what internal reconstructions or what or-
ganic phenomena presage the act of molting; and observers cannot agree
even on how the animal escapes from his chitinized confines when they

82 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

become insufficient for his needs. Wohlgemuth (1914, p. 43) from his
observations on Cyprinotus incongruens, believed that the animal shed
the antennules first, then the other appendages in order toward the rear.
Schreiber (1922, p. 491) observed the molting of Hucypris virens and
concluded that the rear appendages were the first to be freed from the
old skeleton and the antennules were last. It is possible that the process
varies with different species.

The writer has observed one animal complete the molting, and has
killed three others in various stages of the process. The molting takes at
least two hours. It is accomplished by barely perceptible movements with
prolonged intervals in which the animal is apparently motionless. A pe-
culiarity that conspicuously marks the complicated procedure is that the
old shell, the old body wall, and the old covering of the appendages, all
are left lying approximately in their original attitude. It requires close
inspection indeed to determine how the animal, now crawling away and
secreting a new covering, could have escaped at all!

The ostracod which completed the molting was first observed lying on
its side at the bottom of a culture dish. The branchial plates were in nor-
mal rapid motion, but the animal did not attempt to right itself with the
antennae. The valves were slowly spread abnormally wide, so that the
animal came to rest on its back with the appendages upward. The first
break of the covering occurred when the chitin lining of the left valve
suddenly burst and the new shell thrust forward about 10 p, as though
propelled by a spring. This was followed by a rippling motion in the right
valve, and a short time later the new valve emerged on that side. Thirty
minutes had elapsed since the observation began. The edges of the new
valves were remarkably smooth, not crumpled at all. Slowly the rift in
the chitin lining spread toward the rear, following the inner margin of
the ventral edges, and allowing more of the new valves to spring out.
The outward movement of the new valves seemed to create a tension
on the body wall in the region of the head. The body wall separated from
the lining of the valves in the dorsal part of the head region. The an-
tennules were then withdrawn meticulously and ever so slowly from their
enclosing sheath, like fingers from a glove. The antennae followed, and
then the other appendages. The shell in the posterior region was freed
from the old chitin lining. This lining then acted as a spring, permitting
the old body wall and appendage coverings to be pushed upward, away
from the body. Using the antennae, the animal rather freely clambered
out through the front of the old skeleton. As soon as the animal was
free, the elastic lining of the old valves sprung back into place, partially
concealing the splits which served as an exit. Even a coating of the liga-
ment was shed, so that the valves remained united. The animal lay mo-
tionless for some time, then gingerly brought itself upright with the aid

BIOLOGY 83

of the antennae and began feeding. It had successfully passed from the
eighth to the ninth instar stage. The animal was eating two hours and
fifteen minutes after it was first observed, but the writer does not know
how long it had been in the original position on its side.

Fic. 33. Swimming movements of Cypridopsis vidua. A. The forward extension
of the natatory setae. B. The backward thrust of the antennules and antennae.

A second specimen was killed for study in the first stages of the seventh
molting. The new valves had not yet broken through, but were seen to be
buckled under the old valves in three broad warps. The old valves were
not extended as far as were those of the first case.

The third specimen was killed when the two valves had begun separa-
tion from the old ones. It was the eighth molting. The left valve was
completely free, while the right had only broken through at the anterior
edge. This unsymmetrical progression made the animal appear to have
three valves, one right and two left.

The fourth specimen was also in the eighth molting. The two new
valves were still imprisoned in the posterior region, but the antennules
were completely withdrawn, and were found to be complete, even to the
natatory setae.

It would appear from these observations that the process of molting
is somewhat irregular, depending upon where the chitin happens to split.

By the time the new shell emerges from the cast-off skeleton, it is rigid ;
however, no study was made of the rate of addition of calcium carbonate.
This could be done by using doubly polarized light, and noting the
appearance and spread of the lighted areas. Fassbinder (1912, p. 555)
stated that the precipitation began in the anterior end of the shell.

SWIMMING

The ostracod propels itself forward in swimming by swift, powerful
strokes of the antennules and antennae. The very long setae of the an-
tennules are thrust quickly upward and back, and in unison the setae of

84 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

the antennae are thrust downward and back (Fig. 33). This four-oared
motion of the two antennules and two antennae permits the animal to
swim freely at an observed speed of 10 mm./sec. when alarmed, despite
the heavy burden of the shell.

The nauplius or first instar spends most of its time swimming, and is
seldom observed on the bottom of the aquarium. The adult usually swims
short distances, stopping for longer periods of time to feed on the bottom.
However, when the water close to the bottom becomes foul and low in
oxygen, the adults also spend much of their time swimming near the top,
and feed on the algae on the sides of the aquarium.

WALKING

The second thoracic leg seems to be essential to the walking gait of
the adult ostracod. The younger instars, in which the second leg has
not developed, spend little time on the bottom. Their locomotion on the
floor of the aquarium appears limited to clambering with the two an-
tennae. The amount of time the animal spends in walking increases with
each instar, and many adults do no swimming for long periods of time,
but walk over the surface of the algae and even burrow into it.

The motion of the ostracod in walking is rather smooth, despite the
fact that it “hops” rather than ‘“ambles.” The legs move in unison rather
than alternately. To understand the motion, let us follow through a com-
plete cycle. The claws of the antennae support the weight of the an-
terior part of the ostracod, while the claws of the second thoracic legs
similarly support the posterior part. The complete cycle of the motion
involves six phases, as follows: (1) the body is horizontal, the second
legs are so strongly flexed that the weight rests on the convex dorsal edge
of the claws, and the antennae are partially flexed; (2) the antennae are
straightened, elevating the front part of the shell; (8) the extensor mus-
cles of the second legs contract, rocking the end claws forward on the
convex surface, and pushing the body forward; (4) the end claws of the
antennae are shifted forward to a new position; (5) the flexor muscles
of the antennae contract, pulling the shell forward; (6) the second leg
is flexed and shifted forward, bringing the animal to the first position
again (Fig. 34).

PH ToLERANCE

The pH value was determined for the water in an aquarium where
the Cypridopsis vidua fauna was increasing rapidly, and was found to be
7.8. The pH value of water from Crystal Lake, Urbana, Lllinois, where
Cypridopsis is abundant, was found to be approximately 7 in the summer.

Reed and Klugh (1924, p. 274) conducted faunal surveys of two pools
in close proximity, one in limestone and one in granite. Cypridopsis vidua

Fic. 34. Walking movements of Cypridopsis vidua. A. At rest. B. Antennae ex-
tended to lift the anterior end of the body. C. Antennae thrust backward and the
body rocked forward on the end claws of the second thoracic legs. D. Antennae
lifted free and extended to new positions (from ¢ to d). E. Flexing of the anten-
nae and the farthest extension of the second legs. F. Second thoracic legs lifted
free and brought forward to new positions. The cycle then repeats from B. Fig. A.
shows the antennules in position to “explore” the area immediately in front of
of the ostracod. The muscles shown are those used in each phase of the move-
ment.

was reported in the granite pool where the pH was 6.2 to 6.8, but was
absent from the limestone pool.

Klugh (1927, pp. 42-48) used HCl and NaOH to control the pH in a
set of experiments to determine the pH range of freshwater ostracods.
He found that Cyprinotus incongruens could survive two days in pH = 4,
one day in pH = 10, and none were killed in pH =7 and pH= 8. Cypria
exsculpta could survive one day in pH = 4, seven days in pH = 10, and
none were killed in pH = 6 and pH = 7. His specimens were from pools
having pH less than 7.2.

No experiments or collections have ever been made to determine if a
species can become adapted to pH values outside its experimental range.
This would be especially valuable in the interpretation of the environ-
ments of fossil species.

HEAT AND Coup TOLERANCE

The tolerance of heat and cold differs for species reproducing in the
early spring and those reproducing in summer. The forms which repro-
duce in the cold temperatures of early spring can withstand being frozen
fast in the ice, but expire at warm temperatures. On the other hand, the
species which typically reproduce during the hot summer months die in

[85 ]

86 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

very cold water, but maintain normal living processes at very warm
temperatures.

Cypris ornata O. F. Miller and Cypris virens Jurine could only be
sustained at a temperature of 16-18° C. for a maximum of three days,
according to Schreiber (1922, pp. 497-98). Cypridopsis vidua and Cypri-
notus incongruens Ramdohr, “summer” forms, were placed in the sun
in July where the mid-day temperature was 34° C. and continued swim-
ming about freely; under the same conditions Cypris ornata and C. virens,
“early spring” forms, ceased all swimming activity and crept about on
the floor of the container.

The tolerance of cold is phenomenal for certain species. Korschelt
(1914, pp. 106-20) conducted a series of experiments with Cypris virens
Jurine and Cyclocypris laevis O. F. Miller. At 7 p.m. on January 23
ostracods were placed in water with a temperature of 4° C. and the water
was then frozen; on January 25 the ice was melted and one Cypris and
one Cyclocypris were still living; observations were continued until Feb-
ruary 24, a which time both animals were still strong. In a second experi-
ment, ostracods were placed at 7 a.m. on January 24 in water at a
temperature of 4° C., the water was frozen, and the ice was broken into
pieces so that no trace of water could remain; on January 26, one Cyclo-
cypris was still living and appeared completely fresh; it was still living
on February 24 when observations were discontinued. In a third experi-
ment, at 9:30 p.m. on February 5 ostracods were placed in a small quan-
tity of water at 4° C., which was then frozen into a piece of ice the size
of a walnut; on February 6 four Cyclocypris and two Cypris were still
alive, and were still living on February 26. Schreiber (1922, p. 498) found
that Cypris ophthalmica Jurine could also be frozen fast in ice without
apparent ill effects, but that individuals of Cyprinotus incongruens, a
“summer” form, showed marked effects when brought to a temperature
of 2° C. They sank to the bottom and their color faded to the yellowish
tint typical of dead individuals of the species; they crept slowly about
the bottom with their shells half-open. They could not withstand the tem-
perature of 2° C. for longer than twenty-four hours. Other Cyprinotus
icongruens were placed in a container which was slowly cooled to 2° C.
during a six-hour period; the temperature was maintained at that level
for two to three hours, then gradually warmed to 11° C. The animals died
after two to three days.

No experiments have been made with Cypridopsis vidua to determine
its cold temperature tolerance. The writer has taken samples from Crys-
tal Lake, Urbana, Illinois, in early December when the temperature of
the air was between 5 and 10° C. The Cypridopsis vidua in the samples
were very few, about half adults and half intermediate instars. All of

BIOLOGY 87

them were very sluggish when first examined, but upon warming to room
temperature they became quite active.

RELATION OF HEAT AND GROWTH

The writer found that in laboratory cultures kept at room temperatures
Cypridopsis vidua developed from the egg to sexual maturity in approxi-
mately one month. Ferguson’s (1944, p. 719) records of field collections
indicate that the species in nature requires over two months for full de-
velopment. There is no information on the quantity or quality of food
supply available for the ostracods in Ferguson’s data, so that food can-
not be ruled out as a contributing factor to the slower growth rate. How-
ever, the writer believes that the temperature effects were chief factors
causing the difference in rate.

Klugh (1927, p. 46) has done the only quantitative work on the re-
lation of heat to the rate of growth in ostracods. He kept twenty 1mma-
ture instars of Cyprinotus incongruens Ramdohr at a temperature of 12
to 13° C. for one week, and twenty other instars of the species at a tem-
perature of 17 to 31° C. during the days and 7 to 12° C. during the nights.
The ostracods at he lower temperature showed an average increase of
204 for the week, while those at the higher daytime temperature in-
creased an average of 553 during the same period. Food and light were
the same for the two cultures.

It is apparent that the relation of heat to the ostracod in nature is a
complex ecological problem. If we consider the ostracod as a faunal con-
stituent, then the amount of heat supplied to its environment will affect
the amount and type of its food supply, the thermal gradient of the
water, the nature of the bottom sediments, the activity and food require-
ments of its natural enemies, the number of generations in a given time,
the amount and type of protective screening vegetation, the hydrogen ion
concentration of the water, and possibly other factors. The increase of the
species is thus much more complicated than the growth of the individual
in its relation to heat. Field records indicate that each species reaches its
greatest abundance when the temperature of the water is most favorable
for its reproduction and growth, but specific data are insufficient to sub-
stantiate this conclusion as true without exception. All available informa-
tion on habitat and biotic relationships should be considered in the study
of this problem.

PHOTOTAXIS

Cypridopsis vidua individuals can be segregated in a culture dish
by exposing a large area of the dish to a very strong hght for a few
minutes. The animals will all be found in the unlighted area, away from

88 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

the source of light. If half of the area under a flat-bottomed dish is made
white and the other half black, and the whole is exposed to strong over-
head light, more animals will be found over the black nonreflecting sur-
face after a few minutes. This has proved to be an efficient means of iso-
lating ostracods in a culture, so that individuals can be obtained for study.
Yet if placed in darkness for an hour, most individuals will immediately
head toward light of any intensity.

Towle’s (1900, pp. 345-65) experiments with this species also showed
that the positive response is temporary (longer in duration when the ani-
mal has not previously been exposed to light), while the negative one
persists as long as the animal is in motion. The animal’s direction is re-
versed when the animal is mechanically stimulated. Towle concluded
that mechanical stimulation is responsible for reversal of heliotropic re-
action, but the writer has observed that reversal of direction will result
with mechanical stimulation with even illumination, so that light cannot
be credited as a factor.

Yerkes (1900, p. 412) found that Cypris virens swam the second half
of the distance toward the light source more rapidly than the first half,
and that it swam quicker in strong than in weak light. Thus the intensity
of the light is proportional to the intensity of the stimulation effect it
produces on the ostracod.

The chemical condition of the water also appears to be a very decisive
factor in phototaxis. Ostwald (1907, pp. 384-408) found that with other
Entomostraca, the addition of macerated quince to the water changed
a strongly positive heliotropic reaction to a strongly negative one, and
vice versa, with the temperature maintained the same. He also found that
temperature increase can change a positive to a negative reaction, and vice
versa. These results emphasize that one series of observations is entirely
inadequate to describe the phototactic reactions of a species.

The strength of the initial heliotropic response is phenomenal. Yerkes
(1900, p. 419) found that when an acid barrier is placed in their path,
the directive influence of light is sufficient to lead ostracods (Cypris
virens) to their destruction. Franz (1910, p. 331) also found that the
phototaxis of lower animals is abnormally strong, stronger than the drive
of hunger or sex. It should be borne in mind in any ecological study,
therefore, that the directive power of the hight may bring ostracods into
harmful environments which they would otherwise avoid.

RELATION OF LIGHT AND GROWTH

Cultures of Cypridopsis vidua placed in full sunlight during the day
did not increase in numbers, and some of them died after several weeks.
The aquaria placed in the sunlight was not provided with any large types
of vegetation or artificial shading. Cultures placed in strong indirect sun-

BIOLOGY 89

light survived for two years. These results cannot be attributed wholly
to the effect of light, for no means were used to control the temperature
of the aquaria placed in the sun, and undoubtedly the water temperatures
became unfavorable during the middle of the day. The experiment shows
that ostracod cultures can survive for as long as two years without direct
sunlight.

These results of the ultimate increase of cultures is at variance with
the results obtained by Klugh (1927, pp. 45-47) on the individual growth
rate of Cyprinotus incongruens Ramdohr as affected by light. His elab-
orate experiments were so designed that temperature and food supply
was constant for all cultures. One typical experiment showed that in-
stars in full light grew an average of 189» per week; those in 50 per cent
grew 155 per week; those in 20 per cent light grew 92» per week; and
those in total darkness only 57» per week. Klugh also found that the in-
stars were affected by the color of the light. Filters of approximately equal
light transmission were used, and the ostracods subjected to red light
increased an average of 83.4u per week, to green light an average of
180.7 microns, and blue light an average of 205.9 microns.

The light requirements vary for the species. Some species of fresh-
water ostracods have even been described by Khe (1931, pp. 161-68; 1934,
pp. 193-99; 1936, pp. 1-13) from caves and other underground waters of
Europe. No experiments have ever been conducted to determine the
effects of light on the growth rate for these species which are adapted to
total darkness.

RATE OF REPRODUCTION AND LIFE SPAN

On December 2, 1947, the writer isolated ten adults of Cypridopsis
vidua into separate small vials. Since this species is parthenogenetic, all
the young produced in each vial would represent a clone. Each individual
was supplied at the beginning with a culture of algae for food. Distilled
water was added from time to time to make up for losses by evaporation.
The conditions of light, temperature, and aeration were maintamed.the
same for all ten ostracods during the course of the experiment.

At the end of the thirty-four days, an examination of the contents of
each vial was begun. All of the living ostracods were removed and meas-
ured, to determine what stages they had reached. Although the females
were in uniform environments, there were great variations in the number
of young produced. This may be attributed, in part at least, to differences
in their ages, for the adults were originally selected at random. The re-
sults of the final counts are shown in Table 1. Three of the females died
without leaving any progeny, while one produced fifty-three young. The
clone in vial B contained offspring in eight different stages; and although
three of the young had already reached maturity, it seems highly unlikely

90 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

TABLE 1
Instar Total

Vial 1 2 3 4 #5 6 7 + 8 Adults Young Days Remarks
A < 16 2 2 1 1 28 34

B 6 5 6 10 7 13 3 4 53 35

C 4 2) eee 1 10 35 2 fertile eggs
D 1 3 5 1 1 10 35 3 fertile eggs
E 5 2 1 il 8 36

F 2 1 2 36

G 2 1 4 7 36 Female died
Total
voung 1 15 14 27 16 16 19 7 3 118

that any of the younger instars were granddaughters of the original
ostracod. The clone in vial C ranged from fertile eggs to a seventh instar.
The spacing of the young in vial E indicates that the eggs were not laid
continuously, but in groups at intervals. It seems highly probable that the
females in vials F and G were older, for they ceased egg production
shortly after their isolation.

The results of the experiment indicate that: (1) the female lays eggs at
intervals, and not all at one time; (2) the complete cycle of growth can
be completed in thirty-five days; (3) a female may survive beyond her
capacity to lay eggs; and (4) under favorable laboratory conditions,
ostracods will reproduce during the winter, although in nature they do not
normally produce young during that season.

There are very few studies of the occurrence in nature of Cypridopsis
vidua. Wohlgemuth (1914, p. 55) maintained the species in a culture
throughout the year, but only found it in nature during the months of
May, June, July, and August. Miller (1900) also reported it in Septem-
ber. Ferguson (1944, p. 719) found adults in nature from February
through December, late instars in April, May, and June and in August,
September, and October, and young instars in April and August. He
believed from his investigations that there are two broods per year for the
species.

The longest life span recorded for Cypridopsis vidua is 134 days re-
ported by Korschelt (1920, p. 73). Schreiber (1922, p. 504) found that
the animals lived as adults 113, 53, 47, 40 and a fewer number of days.

We see, therefore, that there must either be more than two broods per
vear to maintain the species, or the development of the eggs must be

BIOLOGY 91

greatly retarded in cold water during the winter. Ferguson’s observations
of young instars in April probably corresponds to the general burst of
life in fresh water in the spring. The warming of the upper layers and the
sudden appearance of additional food must have affected even the small
pond which Ferguson used for his study. The writer obtained plankton
samples from Crystal Lake, Urbana, Illinois, a small body of water with-
out active flow. Samples were taken at intervals from April through
October, 1947, and from March through early December, 1948. Both
young instars and adults of Cypridopsis vidwa were present in all collec-
tions, although the numbers present in the spring and summer months
were about ten times those in December.

It would seem that reproduction takes place the year around in nature,
but the survival rate is much greater during the favorable spring and
summer months than during the rigorous late fall and winter months.

Foop

The food supplied to cultures of Cypridopsis vidua consisted of the
small spherical algae which Klugh (1927, p. 77) included under the term
“palmella forms.” No attempt was made to follow these algae through
their reproductive cycle to determine their generic status, but it is as-
sumed that they are included in Klugh’s listing of palmella forms:
Palmella, Chlorella, Gloeocystis, Chlorobotrys, Botrydiopsis, Chloros-
phaera, Palmellococcus, Plewrococcus, Schizochlamys, Sphaerocystis, Tet-
raspora, Chlorococcum, Planktosphaeria, Protococcus, and Heterococcus.

It was found advantageous to raise cultures of the algae. The algae
were collected from the same habitat as the ostracods, and small amounts
were added to the aquaria. At the same time were added small quantities
of detritus derived from boiled egg yolk which had been grated into
water, decomposed bacterially for a month at warm temperature, and
strained through a 100-mesh screen. It was found that this material gave
greater growth of algae than similar additions of humus or of macerated
leaves. It was also found that the growth was slightly greater in pond
water than in distilled water. No experiments were made with prepared
chemical solutions, such as Molisch Solution. The algae increased in
sufficient quantity so that amounts could be withdrawn for stocking other
aquaria before adding the ostracods. In some cases the algal increase in
the water was sufficient to offset depletion by the ostracods, but fre-
quently secondary additions from the stock of algae were found to be
necessary.

An examination of the stomach contents in needle dissections of ani-
mals collected at Crystal Lake, Urbana, Illinois, showed that the diet
of Cypridopsis vidua also includes the following: diatoms of the family
Naviculaceae, including the genera Pinnularia, Brebissonia, and Am-

92 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

phora; Chlorophyaceae of the family Desmidiaceae, tentatively identified
as Tetmemorus and Gymnozyga; and one flagellate, probably Trachelo-
monas.

Klugh (1927, p. 54) listed palmella forms, Chaetophora elegans, and
Conferva bombycina tenuis from his examination of Cypridopsis vidua
stomachs. Sharpe (1918, p. 798) reports that the species has been observed
making skeleton leaves.

The food of fresh-water ostracods in general was investigated by Wohl-
gemuth (1914, p. 20). He stated that of twenty-one species he was able
to raise in cultures, only Notodromas monacha (QO. F. Miiller) could not
be raised on an altered diet. He found that the other species could also be
brought to a diet of potato, crushed snails, or horse flesh. This is not in
accord with the writer’s experience with Cypridopsis vidua. All cultures
died out when supplied with meat, both cooked and raw, and in varying
quantities.

COMMENSALISM IN OSTRACODS

There are no biocoenotic relationships or associations known for Cy-
pridopsis vidua.

No ostracods are known to have adopted a parasitic habit, although
Marshall (19038, pp. 117-44) first described Entocythere as a parasite of
the crayfish Cambarus. This relationship was later shown by Hoff (1942b,
pp. 63-73) to be only commensal.

There are only two commensal genera of fresh-water forms reported.
One of these, Sphaeromicola, is limited to Europe, and the other, Ento-
cythere, has only been found in the United States and Mexico. All the
relationships have been with other crustaceans, with the ostracod clinging
to appendages of its larger relative to take advantage of the currents of
water with incoming food. Sphaeromicola topsenti Paris lives on the
isopods Caecosphaeroma burgundum Dollfuss and C. virei Dollfuss (Klie
1926, p. 54). Sphaeromicola dudichi Klie clings to the burrowing amphi-
pod Chelura terebrans (Klie, 1938b, pp. 317-22). The species of Ento-
cythere are commensal on the crayfish Cambarus (Hoff 1942b, pp. 63-73;
Roija 1942, pp. 201-4).

Taxonomic work on the American ostracods has been limited, and other
instances of commensalism, and possibly parasitism, may be discovered.

PARASITES OF OSTRACODS

Although no parasites were found in the writer’s collections of Cypri-
dopsis vidua, internal parasites have been reported by Hoff (1942a, p. 10)
in fresh-water forms from Illinois.

Larval stages of cestodes and acanthocephalans have been found para-
sitizing fresh-water ostracods. The cestodes were species which as adults

BIOLOGY 93

parasitize aquatic birds. Mrazek (1890, pp. 226-48) found cercocysts of
Taenia coronula Dujardin in the ostracod Cyclocypris ovum Jurine.
Lindner also found larvae of Drepanidotaenia gracilis Keal in Candona,
Dolerocypris, and Cypria (Klie 1926, p. 53).

The ostracod Cypria globula has been found by Ward (1940, pp. 327-
47) to be the first intermediate host of Neoechinorhynchus cylindratus
(Van Cleave), the adult of which parasitizes the largemouthed black
bass. Hoff (1942a, p. 10) also found acanthocephalan larvae in several
species of ostracods.

There are also ectoparasites found on fresh-water ostracods which may
not be very damaging to their hosts. The ciliate protozoans Rhabdostyla
ovum Kent and Opercularia lichtensteini Stein have been found on Cy-
pridae (Klie 1926, p. 53).

Marine ostracods are beset with additional types of parasites. G. W.
Miller, found Cythereis badly damaged by undetermined nematodes
(Klie 1926, p. 53). Monod (1932, pp. 1-8) discovered that Cypridina ser-
ves as host for two different parasites, a copepod larva of the family
Choniostomatidae and an isopod (Cyproniscus) of the family Crypto-
niscidae.

V. Immature Stages

The growth of an ostracod becomes apparent only at intervals when the
animal sheds the old carapace and secretes a new one. Each instar, or molt
stage, must be regarded as a completely integrated living unit, perform-
ing locomotion, feeding, respiration, and the other life processes. Each
molting of the ostracod introduces an animal differing from that of the
previous stage. The molting is quickly followed by a revision of the
tissues, before the new covering of chitin is secreted. Entire new append-
ages and organs are added, and the structure of previous appendages is
drastically changed. A most remarkable feature of this discontinuous
growth system is the change in function of an appendage, which may be
used as a walking leg in one instar and as an accessory feeding mechanism
in the next.

The morphology of the various instars has been described by Claus,
G. W. Miller, Schreiber, and Scheerer-Ostermeyer. At first, a comparison
of their reports seems to show great variance. However, a detailed com-
parison of their descriptions reveals that the differences arise not from
the observation of what is present in any one instar, but from the inter-
pretation of the appendages in immature individuals. The same append-
age which Claus describes as an incipient second leg is referred to by
Miller as an incipient furea. Thus the order of appearance of the various
appendages differs considerably according to different authors, al-
though their observations are in agreement.

Claus (1868, pp. 151-66) made the first extensive study of early instars.
He gave the following order of appearance of the appendages and sex
organs, based on Cypris ovum and C. fasciata:

Instar Appendages —
1 Al An Md

2 Al An Md (Mx) .... (L2)
3 Al An Md Mx .... (L2)
4 Al An Md Mx (L1) (L2)
5 Al An Md Mx Ll (TD. cole + aven ee weak nar eee eee (Fe)
6 Al An Md Mx Ll L2 (5S Puke aera ote gaeeretne Fe
7 Al An Md Mx Ll L2 L3 (ORL co ake g Sack tetee rere Fe
8 Al An Md Mx Ll L2 L3 Ov (Gn) oo aeteledie
9 Al An Md Mx Ll L2 L3 Ov Gi: «oka ee
Al = antennule Mx = maxilla Ov = ovary
An = antenna Ll = first thoracie leg Gn = genitalia
Md = mandible L2 = second thoracie leg Fe = furca
( ) = anlagen, incomplete L3 = third thoracic leg

[ 94 ]

IMMATURE STAGES 95

The next contribution was that of G. W. Miiller (1894, p. 182), who
gave the following sequence for the Cypridae:

Instar Appendages —
Al An Md

1

2 JTS aN Stabe) Es RR OIA Ea) a (Fe)
3 PRUE VEC INI WAU See cstete Siew. ba duane Canad «adage deeweed (Fe)
4 eerie eNike Ae ie caine obec ode ee eh ea ueleb es (Fe)
5 Al An Md Mx Ll (12) ana Wr a oes gr ear CP a Nl Fe
6 Al An Md Mx Ll EZ Rr la hee cat ies oe aah aah ateagie Sa Fe
a Al An Md Mx Ll L2 ae (CON) ie geese ean Fe
8 Al An Md Mx Dt L2 L3 Ov (Gn)........ Fe
9 -Al An Md~ Mx Ll L2 L3 Ov Gip <a ee

This system was followed in general by Schreiber and Scheerer-Oster-
meyer later, and it agrees with the observed facts for Cypridopsis vidua.
It will be seen that the number of appendages for each stage in the two
analyses is the same. In Miiller’s system the furca appears early and the
body appendages are added in orderly sequence from the anterior to the
posterior, which agrees with the pattern observed for other crustaceans.

The orderly appearance of new appendages led Miiller to propose a
theory that would account for the rate at which they appear. One new
appendage is added at each molt stage except the third. Miller (1894,
p. 179) postulated that the second maxilla was lost late in the history of
the ostracod, and that the original ostracod added one appendage at each
instar. With this second maxilla (which does not develop in the present
ostracod) represented by a dash, the sequence in the ostracodal ontogeny
assumes the orderly arrangement:

Instar Appendages and Organs —
Al An Md

1

2 7 ViameATIMV d -05| AVI Vink vaplct eas siete oo a ieia cr oes we cata ont dk aaa tara es (Fe)
3 PmmeTine VEC | Vine) Mrs ace ie eee ese See ac ee bla awe a (Fe)
4 Al An Md Mx so (ey) eer aie he RC eee cre (Fe)
5 Al An Md Mx — tee een race wes Fe
6 Al An Md Mx — Ll 1 it 9 rene cere meena Fe
fi Al An Md Mx — Tad L2 Lo (OV) ee pce Be
8 Al An Md Mx — Ll L2 3 Ov (Gn)... Fe
9 Al An Md Mx — Ll L2 L3 Ov Gn ... Fe

Whether Miiller’s postulate is justified or not, it offers an explanation of
the appendage sequence.
First INSTAR

The shell of the first instar, or nauplius, is wellrounded, reflecting the
elliptical shape of the egg shell from which it hatches. The shell is very

96 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

weakly calcified. The eye is large in relation to the size of the shell. The
three pairs of appendages are antennules, antennae, and mandibles. Each
antennule consists of four podomeres set upon a stump or projection of
the body, so that it functions as five podomeres. There are only five setae,
three of which are terminal (Chart 4). The antenna has two podomeres
set on a long projection from the body. The terminal podomere has a
constriction one-third of the length from the end, but does not appear to
be completely divided. It is of note that the penultimate podomere bears
a short cylindrical seta on its ventral border, which later develops into
the “sense club.”” The mandible is pediform, composed of two short podo-
meres set on an elongate extension of the body. There is a strong seta
at the end of this backwardly directed appendage. The base of the mandi-
ble has an anterior lobe which lies at the side of the mouth.

The mouth itself is set far back on the body, in the posterior half of
the shell. An enlargement of the alimentary tract can be seen through the
transparent shell, with only a slight medium constriction to set it off into
a stomach proper and a rear gut. There are two lateral livers opening into
the stomach, but they do not reach to the epidermis of the valves. Schrei-
ber (1922, p. 511) isolated first instars of Cyprinotus incongruens with-
out food, and found that they molted at the same time as those with
adequate food supply. It is entirely possible that the ostracod passes
through the first instar stage utilizing remnants of the yolk as nourish-
ment.

Excretory gland B has been described for Cyprinotus incongruens in
the first instar (Schreiber 1922, p. 509), but it could not be discerned in
stained total mounts of Cypridopsis vidua.

SECOND INSTAR

The first molting of the valves initiates the second instar. The shell is
larger and slightly thicker. The rim of the shell is still very simple. The
eye is approximately the same size as in the first instar, and is still located
near the middle of the shell. The antennule is still composed of four
distinct podomeres and a basal projection of the body. The antenna is
now made of three distinct podomeres set on a long projection from the
body. The “sense club” is now on the antepenultimate podomere, so the
division of the terminal podomere resulted in the increased number in
this instar. The terminal claws of the terminal and penultimate podo-
meres are only weakly developed as setae. The mandible is greatly altered
from its pediform structure of the first instar. The basal podomere is
completely set off and equipped with incipient teeth at its distal end.
The leg-like development which was directed posteriorly in the previous
stage is turned 180° about the base, and now becomes modified as the

IMMATURE STAGES 97

palp. This palp, composed of three distinct podomeres, is set onto a projec-
tion of the basal protopodite, and represents the endopodite. There are
also the beginnings of the mandibular exopodite plate.

The anlagen of two new appendages are interpreted as the maxilla and
the furca. The maxilla is a swollen section of the body with a nipple-
shaped pointed projection at the anterior ventral corner. There is also a
slight lobing of the body in the dorsal posterior area, which may be inter-
preted as the anlagen of the exopodite plate. The furea is represented by
a strong stump-like projection of the body with a long terminal seta ex-
tension (Chart 4).

The mouth has shifted to the middle of the body. The digestive system
more closely resembles the final arrangement. The livers are still simple
lobes and do not reach the epidermis of the valves.

THIRD INSTAR

The third instar is marked by the further development of the append-
ages already present, and no new anlagen appear. The antennules con-
sist of the same number of podomeres, and the main change is the in-
creased length of the natatory setae. The antenna has the same form,
but the natatory setae appear in abbreviated length. The mandible is
also essentially unchanged. The basal podomere is stronger and more
elongate, of approximately the definitive form. The end of the maxilla is
divided into “masticatory” processes but without a palp. The exopodite
plate bears six setae. The furea is of the same form as in the second in-
star, a stump of the body with a long, strong seta, and still has not
assumed its definitive form.

There is a pair of knob-like body extensions between the maxillae and
the furcae which Claus (1868, p. 155) interpreted as the beginnings of
the first thoracic legs. These lobes are not sufficiently developed to be
regarded definitely as the anlagen of the first legs.

The mouth is still in a median position.

FourtH INSTAR

The outline of the shell of the fourth instar (Chart 4), like those of the
other instars, was drawn from all measurements of all specimens plotted
in Chart 1. This composite outline does not show any inbuckling of the
ventral border as was described by Claus (1868, p. 156) and by Schreiber
(1922, p. 519).

The antennule has five podomeres. The antenna has the same approxi-
mate form as before, but with stronger end claws and three natatory
setae. The second podomere of the protopodite of the mandible is now
separated from the basal podomere, but the general form remains the

98 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

same. The maxilla approaches the definitive form with the addition of
an unmembered palp, and the increase in the number of setae on the
respiratory plate.

There is a definite anlage of the first thoracic leg, a roughly triangular
plate with the forward corner attached to the body, the ventral lobed
corner hanging free, and the rear corner equipped with a short curved
claw. The ventral part is the incipient “masticatory” process of the pro-
topodite, and the rear part is the endopodite.

The furea is strongly developed, proportionately larger than the final
form.

The mouth is shifted slightly forward. The livers still do not reach
into the valves. The cerebrum can be discerned in this stage.

Firru INsTar

The shell of the fifth instar has a more complex rim and a thicker
structure. There is also a better-defined color pattern, very similar to
that of the adult.

The antennule is composed of the same five podomeres with an in-
crease in the length of the natatory setae. The antenna is also changed
very little, with the three natatory setae reaching to the mid-point of the
end claws. The mandible is increased only in size. The palp of the maxilla
is now divided into two podomeres, and the respiratory plate is larger
and equipped with approximately ten setae. The first thoracic leg is
further developed. The “masticatory” process bears three short setae at
its distal end. The endopodite has two distinct podomeres set onto a
projection of the protopodite, and bearing a strong curved claw at the
end. This backwardly directed pediform process appears to perform the
functions which are later taken over by the second thoracic leg.

There is an anlage of the second thoracic leg. This is an elongate, back-
wardly directed process of the body, terminating in a very blunt claw-like
process. It 1s attached above and immediately behind the first thoracic leg.

The furea approaches the definitive form, with the terminal seta re-
duced to the “flagellum” typical of the Cypridopsinae.

The liver extends laterally into the epidermis of the valve, but is not
recurved toward the ventral posterior end.

StxTH INSTAR

In the sixth instar for the first time the ostracod has all of the append-
ages present. The remaining ontogenetic stages show further development
of the appendages and the anlagen and completion of the sex organs.

The antennule has six podomeres with well-developed natatory setae.
The antenna has the same number of podomeres, and the natatory setae
reach to the end of the terminal claws. The mandible, which already

IMMATURE STAGES 99

reached its definitive form, is slightly larger. The maxilla also has
reached its definitive form in the previous instar, except for the number
of setae, which are increased in this instar. The first thoracic leg has a
“masticatory” process with a few setae, a three-membered endopodite
with three terminal setae, and the anlage of the exopodite plate. The
second thoracic leg has three podomeres set one to a projection of the
body, and a well-developed, slightly curved terminal claw. There are
also two short setae on the ends of the ventral borders of the penultimate
and antepenultimate podomeres.

The anlage of the third thoracic leg is an elongate, backwardly directed
process of the body with a stubby chitin claw at the end. It resembles
the anlage of the second thoracic leg in the fifth instar.

The furea has the definitive form, including the small seta on the dorsal
edge.

One of the most remarkable features of microtome sections of these
immature instars is the lack of well-defined boundaries for the internal
organs. Differentiation of the cells continues to the adult stage, and the
early anlagen of some organs are difficult to distinguish from the connec-
tive tissue in which they are embedded. The ventral chain of ganglia is
proportionately much larger than in the adult stage. L glands are present
in the large upper lip, but they are not set off sharply from the sur-
rounding tissues. The dorsal wulst is very well developed by this instar.
The livers are distinct, and recurve posteriorly a short distance in the
epidermis of the valves. The muscles connecting the mandibles to the
endoskeleton are very large and well-defined. The eye differs from that
of the adult only in the lesser amount of pigment. The rake-shaped organs
are already well advanced, and possess eight teeth each. The contents
of the stomachs show that the diet is approximately the same as that of
the adult, composed largely of small spherical algae.

SEVENTH INSTAR

The seventh instar has all of the appendages well defined, and the
anlagen of the sex organs. The internal structures become more distinct,
but do not approach the final form.

The antennule is composed of six podomeres set onto a basal projec-
tion of the body. The natatory setae are better developed than in any
previous instar. The antenna approached the definitive form, except for
the protopodite, which is not divided into separate podomeres but re-
mains as an elongate lobe of the body. The mandible is only increased in
size. The maxilla shows greatest change in the exopodite plate, which is
much larger and equipped with the definitive number of setae. The first
thoracic leg is considerably altered; the endopodite palp is no longer
separated into podomeres, and the exopodite plate is much larger. The

100 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

second thoracic leg has the definitive number of podomeres, but the end
claw is proportionately smaller than that of the adult. The third thoracic
leg is small but otherwise complete.

With an acid fuchsin stain the ovaries can be seen in the epidermis
layers of the valves. There is no development of the genital lobes and the
external genitalia.

The upper lip is still much larger than in the final form (Plate 91,
Nos. 390-93). Gland L is present, but lacks the smooth outline which
characterizes it in the adult (Plate 91, No. 390). The dorsal wulst is
very large (Plate 91, No. 392). The excretory glands A (Plate 91, No.
391) and B (Plate 91, No. 390) can be located, but have irregular out-
lines. The anlagen of the spiral canals do not show any passageways
through them (Plate 938, No. 401).

The chitinous rake-shaped organs are well developed and have eight
teeth each (Plate 92, No. 397). The endoskeleton is large and distinct
(Plate 92, No. 395). The teeth of the mandible are arranged in seven
rows (Plate 96, No. 416).

The muscles of the appendages appear to agree with those of the adult,
as seen in the microtome sections (Plates 89-96). The mandibular and the
closing muscles are large and well developed.

The nervous system has all the elements present, but the cerebrum is in
proportion smaller (Plate 90, No. 389) and the ventral chain of ganglia
larger (Plate 92, No. 395) than in the adult.

EIGHTH INSTAR

The eighth instar resembles the adult very closely except for size.
The appendages are all in the definitive form. The greatest change from
the previous instar is the shifting of the mouth forward and the develop-
ment of the genital lobe. Excretory gland C and gland O have not ap-
peared in definite form.

The spiral canals and the other genital organs in the genital lobe are
still only anlagen (Plate 81, Nos. 360, 361). Gland N is also incompletely
developed (Plate 88, No. 380).

The cerebrum is much larger than in the seventh instar (Plate 85, No.
372) and the gangha of the various appendages are more distinct.

THE ADULT

The adult differs from the eighth instar in (1) stronger chitinous devel-
opment of the appendages; (2) completion of the internal glands; (3)
addition of the external chitinous genital structures and the completion of
the sex organs; (4) enlargement of the dorsal posterior portion of the
valves, greater thickness, and more complex rim structures; and (5) the
shifting of the mouth forward with corresponding changes in the shape
of the upper lip.

Chart 1

CHART

SPECIMENS

DISTRIBUTION OF 5090

SIZE

= a
2 3
s >
z = = a] Jele} slant elalafo :
Fd =lolololo. Slo} ofojofol— Blo} ol s| S| =| a] a) e| 5] =
Od ied od i) fd o
S ololofo ojofolo = )2) SIFElsis >
2 elo ee 9] 9} a] oe) n/a] ol alo 2
io} o}o) olo ele} al o| A] Ho] S| el] ol Ola
° ast} eolo =
3 olojolo| ‘lo SS} Fl FS] a) 5 $45
4 =lo}olololo[= =lo/=[o 2 =| «| «al ale] elololo =
3 9|0}/—lo/olo|/—|0) =|clofojo|— Ol} a] | 2) | a) ml ol als fa
= =lolelololofolojojo (ol ofofofo|— =LIPIPI SI Sl alas] ae <
e ololol[ololojojololo/—lojo!— lo] d/o} 0] colo] —[o} —| = =
o >
Ps lololololofofo}o| ololofolojojo| = | et) EA) Ba) be] Ba) Be) Bd a
8 =|=|ofo[=|= ailoloj—[o]— 8
sy lojolo ololo! a
3 lo} oO &
s
g E aE 3
= =[ofolojo}
& | ololofojo $
= olo}olo|—
$ =|< =|=|=|=[e|= 3
CI im elo olfofojojo
all SoS ‘aol —|— 8
ol-|=|= °o}=|=lo}=\o)
ca | a[—lwlo | =|-lo|-|-[el-|-|-|— g
| lolojojo 1] olololololojojofo |
°
fd q =|} o|ro|ra] ou LTT | J-l-l-l-l-i- al —l|-|— I 3
ea |—lo|olo|—|ofo|=|[- ial ofo}e|=lofoj— [ ©
il ololola|=lofal— | [=|=|s=[ol= & <4
=lolofolo|=lolofo|= I =|o[=|=|o VA
°
2 aE —lololo|—|ofo/— —|-[-[olo 2s
ofo|mlolo olololaulol—| ; =
8 ololofol ofolofolo 8
[a 9|o/o|o) Slolo|o
Als ammo g
a o|-|=[o} =[olol=
eet Latalt + my :
[| || Be ololololo o|=lolo im |
2 =lofolofol= | o|—|ofo|=| 3
: to a :
olololo' | olololo
2 +--+ °
2 | =lol= | | a | bs
3 3
: — :
oe eth fsa ene IRASoSS ina ia i
FE SG es =lo[-|-[-T [I =|sJo] = fea | 2
as} ees oS Ye ae [os anf es ncha| nS | Tol=of=|— SOSOCOCEmE l bS
Sl afra[a [pale TEBE CT i lol) 9|=lo} «4 alo} o] = I ol :
BER RAE fic Pal at] |] a] | —|0°|m|o]— wo} ul ofo}—lo |
2 |= eu} caper] | SOdEsoOS aca =|
—|O} a] —|—|—j o] — —|—|N/ ols —|o]o}
2 =|=|<]a/o]=lolo| el of ofa] =Jo|=la|= o
: ae
=o} ei/au|=[a] ofa} | o|=|=|—[o]m|ol =
g ofal—|=[o] o]ofo/=I =[o/=|=[o)/=|=| £0
= o|—|=[a[ofolo} | —|o|=|=]=| =
2 =|=[e]alalo =|=|s[a)a[o 3
ss lo|a[ofo|= o|=|=|ofolol=| 3
a oj alolo =[S[o}o[=|9) Ey
=lolfo|= =|o}o}of=|
Ss i= 2
s =lolo o}=| 3
2 TE = = 2
5 |_| | by
5 a [| l= a= e
° II lo} =|=Io] a Hy
EE | aaulolo O|mlo]—
° = J 3
2 o | [ | ofa] mlo[— al stlolo} & bs
i) =| nu
Sel il ola alolalo} _
3 {| | —lol= o|=lolofeslaul ia Ean |
alt Hel je =[ol+o —[o]ra|+]m[—[ol 5
e) =|} feu} ra| ro —|=-|o!m|—l au] a] of — not
+ iE =la}olalol— =[alrofralalo) iF
ety 2
a ia —|-[olo]— -|-[alclolo is 2
| mO|O =[ololal—lol= a
$ [ iE o|-|= ofolol-|= 2
=i o[-| =|ojolo}
2 2
e 1 al -|9| o|- 3
io] is]
3 3
or = =) oo
a a —lo}oloj= o}—|—
° r - 2
= ia ofofalelol=' =|s[olealer eb
=lel=|n[= a—|=|=l=lo
° ea
= | | BSG 19|r9| [wn] cu] — gg
lofn aul —|m|—|—lo E
° iH — eo
s = [= [ro] —| —lalalo Ey 5
= Sth —|-|o! ofojn =
a Gs olol— Ss g
er + 32
E Tt : + { = io
Tinta: T a5 LL a] —lojm |_| lulO|—|ro s B
3 t pa | -|=|=-|- ofolaj=|— c
ry fa HE Shen 1b m)n|ol|—lo [=[elolafefolea 8 <4
Stel ails ag T o|mlefelololfol— olol=[R ie le 5
seit 1 | = 22 CT =|m|m|+[aulolo alt [mo[o By ic
oy te t|4 et de f u]—jo]— —|-jola rs =
a 2 8 5 ae i GI
s | eas 25s [
e nteweces Slal= fy
8 ean a5 Lt | IE | Ogi s A
° — =o] cul cy a[—lol[m|— oe
2 r_| fs} s<
e}4 _| ia mote eufofolr Edens
ie [sfeu] ofc Ola] ol ou]—[— a
2 y ESAS a | alole —]ra} olor 3 Zz
aE == Ae
2m 2
PtH oO bs
if { a= 4
8 4 {+t g &
2 In Bee sali wo $<
eet PIs oO
3 tal Esl a o sz
| i ©
20 TE Bl i ra] —| Ea tS
} - j++ |- sf nd] ce | ee |—lo oe
1 ei — ; ; ofolrl=[ 3 &
1 sl Yd) FF Ft HE HF ent a [ + [I=[e[-T tT}, 2
Aes i [ SS age EH TT [TI g
= $ 2 8 2 $ 8 3 8 8 § 8 = 5g (8) so (Suhel csiieiccBiciicipeipo mc cmcm cnc mow ENCHIEC MCE ECMEC
Ce er ee ee eet i ee Cnet yo Set emcee y oe rhs Ch tome rp EE sch tS =

- LHOIZH
<— 30nvusia

LenctH —>

VI. Variations in Size of Instars

After a culture of Cypridopsis vidua had been maintained for several
months, the residue in the bottom of the aquarium was removed for ex-
amination. Five hundred valves were selected at random, and outline
drawings were carefully made with the use of the camera lucida. These
drawings were then measured for length, height, and distance from the
anterior edge to the line of greatest height (see Chart 1), using the proper
scale to the nearest 5y interval. Then the area of each drawing was meas-
ured with a polar planimeter, and the readings converted to square mi-
crons.

An effort was made to orient the shells at right angles to the line of
sight when the drawings were made, but some distortion could not be
avoided. The length was measured as the greatest length of the outline
drawing, without reference to the position of the hinge or any other
structure. The height was then measured as the greatest height at right
angle to the length. The lines of length and height were marked on each
drawing, and the distance from the anterior edge of the shell to the line
of greatest height was measured along the line of the length.

A plot of the length vs. height and of the length vs. distance from the
anterior edge to the line of greatest height is shown in Chart 1. It can
be seen that the measurements fall into nine groups, one for each growth
stage or instar. However, there are overlaps in the measurements of
heights for adjacent instars; we can state with assurance that height
alone is not a certain criterion for determining to what instar a given
shell belongs.

There is no direct linear relationship of the length vs. height as shown
in Chart 1. Therefore, the ratio of the height/length is not a constant for
a species, but varies within an instar and also from one instar to another.

Brooks’ Law

Fowler (1909, p. 224) proposed a formula for the growth of ostracods
which he termed Brooks’ Law. He believed that during growth, each stage
increases at each molt by a fixed percentage of its length, which is ap-
proximately constant for the species and sex. This may be expressed as
a formula:

I PO Ore oa 8)

4(n 4
where k is the constant percentage for the species and sex and L, repre-

1 101 |

102 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

sents the length of any molt stage. Skogsberg (1920, p. 132) apphed this
formula to several species of marine ostracods, and the large variations
between computed and observed lengths led him to state that Brooks’
Law should be applied with extreme caution. Table 2 shows the observed
and computed lengths of instars for Cypridopsis vidua. The variations in
the last three stages are too great for the formula to be of value in this
species.
TABLE 2

Comparison of Actual Length with Length Computed by Brooks’ Law.

Instar Observed Length Computed Length *

1 132.2 132.2
2 155.5 158.6
3 188.2 190.3
4 226.8 228.4
5 269.8 274.1
6 333.4 328.9
7 418.0 394.7
8 528.0 473.2
9 617.0 567.8

« Computed from Ly 41) = L (0.20 + 1)

VII. Variations in Shape of Instars

A comparison of shape of two valves is not a simple matter of choosing
descriptive terms. There are no large structures on the surface of Cypri-
dopsis vidua, and this lack of ornamentation compels us to seek criteria
in the general outline of the valves. A complete study should include the
thickness, as well as the length and height, but the writer found it very
difficult to obtain an accurate reading for this factor. With the very
small instars a slight change in the angle at which the valve is viewed
will cause considerable variation in the readings. The thickness in fossil
specimens is found to be deformed more than any other diameter through
the shell, and many species are rarely found without crushed sides. Since
thickness is difficult to measure accurately in modern specimens and has
only limited application to fossil specimens, it was not included in this
study.

“ELONGATION”

A simple height/length ratio for each instar will give a comparison of
the “elongation” of the shell. Table 3 shows this ratio is largest for the
first instar and lowest for the seventh and eighth instars. The first instar
has the most shortened outline, therefore, and the seventh and eighth in-
stars have the most elongated outlines. If we start with the egg, which
has a ratio of 90 to 100 per cent (spherical), we find a general elongation

TABLE 3

Instar Average Height Average Length Height/Length

microns MIUCTONS per cent
1 92.0 132.2 69.6
2 106.0 155.5 68.2
3 123.8 188.2 65.8
4 145.6 226.8 64.2
5) 169.7 269.8 62.9
6 203.8 300.4 61.2
7 250.5 418.0 60.0
8 316.2 528.0 60.0
9 373.0 617.0 60.4

of the outline of the shell through the eighth instar. The adult shell
(ninth instar) is found to have a slightly greater increase in height than
in length from the previous instar.

[ 103 ]

104 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

“BLUNTNESS”

The distance from the anterior edge to the line of greatest height is an
indication of the ‘‘bluntness”’ of the front of the shell. The shell with the
greatest degree of bluntness would have the greatest height at the an-
terior end, and one with a low degree would have the greatest height in
the middle. The “bluntness” factor, it will be noted, can only be applied
to those ostracods with a convex hinge line.

Charts 3 and 4 show the relationship of three factors: length, height,
and distance from the anterior edge to the line of greatest height. These
were plotted on a percentage basis so that direct comparisons could be
made between instars. Chart 2 has smooth curves of height vs. length and
of distance from the anterior edge to the line of greatest height vs. length,
based on the information shown on Chart 1. Chart 3 shows the percentage
relations of the three factors mentioned above, taken at 5- intervals
from Chart 2. Chart 4 gives percentage relations of the three factors
based on the average figures for each instar.

Table 4 gives the ratios of distance from the anterior edge to the line
of greatest height/length for each instar. This shows the greatest degree
of bluntness to be in the third instar, and the least degree to be in the
adult (ninth instar).

These observations hold for the single species under observation and,
whereas other ostracods may show similar progressive shifts in bluntness,
each should be investigated independently before valid generalizations
ean be made.

TABLE 4

Ratios of Difference from the Anterior Edge to the
Line of Greatest Height/Length.

Instar Average Distance® Average Length Distance/Length

microns microns per cent
1 56.4 132.2 42.7
2 64.6 155.5 41.5
3 754 188.2 40.1
4 91.9 226.8 40.5
5 109.7 269.8 40.7
6 139.4 333.4 41.8
7 174.2 418.0 41.8
8 225.9 528.0 42.8
9 282.0 617.0 45.6

a Distance from the anterior edge to the line of greatest height.

‘““ROUNDNESS”

In addition to these measurements of “elongation” and “bluntness,”’
the valves can also be compared for “roundness” from the ratio of the
area of the outline figure to the area of a circumscribed circle. The ratio

Chart 2

SHE
+

al
(ie
—
cea IS
=e
:

_|] SMOOTHED CURVES OF LT ro
Ht Lvs: ho eAND saleaveuD 44

=

| |
|
|

CC CH tT Hott oe TEE
||

=

1

VL
iy
|

|

|

II

i

~

o

=

cS = =
ee cil -u

130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 450 460 470 4680 490 500 5/0 5;

530 540 850 560 570 $80 590 600 610 620 630 640 650

VARIATIONS IN SHAPE OF INSTARS 105

~

TABLE 5

Comparison of Roundness of the Valves.

Instar Average Area Area of Circum- Area of Valve
of the Valve scribed Circle — Area of Circle

sq. & Sq. Ue per cent
1 10,059 13,726 73.3
2 13,227 18,991 69.7
3 18,426 27,818 66.2
4 26,485 40,399 65.6
5 36,479 57,171 63.8
6 54,345 87,301 62.3
7 83,198 137,228 60.6
8 131,963 218,957 60.3
9 180,847 298,993 60.5

for each instar is shown in Table 5. The greatest degree of roundness
is found in the first instar, and the least degree is found in the eighth
instar. The adult has a more rounded outline than the eighth instar, and
the additional space inside is utilized by the sex organs which reach their
full development only in the final stage.

APPLICATIONS OF HUXLEY’S CONSTANT DIFFERENTIAL
GrowTH-Ratio FoRMULA

J. 8S. Huxley (1924, p. 895; 1932, pp. 6-8) first proposed a formula for
comparison of relative growth rates which has been used in many sta-
tistical studies in embryology and growth. His formula is based on the
assumption that the ratio of the relative growth-rate of an organ (or a
particular dimension) to the relative growth-rate of the body remains
constant for a given species and sex. If y is the size of an organ, and x
is the size of the rest of the body, then

a ae
Fp aeG and di = 0G,

where a is the specific constant of the body, 6 is the specifie constant of
the organ, G is derived from conditions of growth, and dt is a time in-
terval. Since the organ and the rest of the body are growing under the
same environmental conditions, the value of G is the same in both equa-
tions, and therefore

dy by

dx ax
Integration reduces this equation to

Yy — Cyrb/a

which can also be expressed as
Y —= Ca*

106 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

where k is the constant differential growth-ratio, by definition the same
as b/a, the ratio of the relative growth-rate of the organ to the relative
growth-rate of the body. C is a constant arising from the integration.

The general application of this formula has been to specific organs as
compared to the rest of the body, but it is equally applicable to other
dimensions as compared to the total length.

It is not to be supposed that the value of k will not vary throughout
the life of any organism, but it is of importance because it gives a quanti-
tative evaluation of growth in any given growth cycle.

The equation y = Cx" can also be written as

log y =k log x + log C.

This form is easier to use in the determination of the values of k and C
over a range of measurements.

It is obvious from Tables 2 and 3 that the height and the distance
from the anterior edge to the line of greatest height do not have constant
ratios with the length throughout the ostracod’s ontogeny. Huxley’s
formula can be applied to determine if the rate of their growth has a
constant ratio to the relative growth-rate of the length. The computed
values for height agree remarkably well with the actual measurements in
all of the immature instars.

TABLE 6
Instar Measured Measured Computed Measured Computed
length height height* distance — distance”
1 132.2 92.0 90.3 56.4 56.2
2 155.5 106.0 104.5 64.6 66.0
3 188.2 123.8 124.2 75.4 79.8
4 226.8 145.6 146.9 91.9 96.0
5 269.8 169.7 171.9 109.7 114.0
6 333.4 203.8 208.1 139.4 140.5
7 418.0 250.5 255.2 174.2 175.8
8 528.0 316.2 315.2 225.9 221.5
9 617.0 373.0 362.8 282.0 258.5
ah = Clk, where C = 1.0965, k = 0.9038.
bd = Clk, where C = 0.4467, k = 0.99. Distance refers to the distance from the anterior

edge to the line of greatest height.

The computed values for the distance from the anterior or edge to the
line of greatest height do not vary greatly from the actual measurements,
except in the adult. The values of C and k in each case are median values
obtained from computations for each instar stage.

We see from this statistical study that the proportions of the ostracod
shell have a nearly constant differential growth ratio in all of the im-
mature instars, but change in the adult.

Chart 3

CHART 3

100 PER CENT 3-FACTOR DIAGRAM

DISTANCE

FROM ANTERIOR EDGE TO LINE OF GREATEST HEIGHT

SHOWING THE PERCENTAGES OF LENGTH,
HEIGHT, AND DISTANGE FROM ANTERIOR
EDGE TO LINE OF GREATEST HEIGHT
FOR EACH 5- MICRON DIVISION OF
LENGTH IN INSTAR STAGES OF
CYPRIDOPS/S VIDUA

LLVVV xX AAT
AO
LAK PAVAVAOAN

LIVIA bie
Lo ee en

WVANIVIVANNVLYY AES (N20

monean EX 2 ae = aN
Sas vat, ss

LVL

NINN AN
LLDLQL-
LARLALA
LAKLALA
ROY) VINX

LEE,
COMPLETE DIAGRAM TO
SHOW POSITION OF THE
ENLARGED SECTION

AY
Lh/ SOARES
AESNSESM Ta AS

{Vi
~ OOK WAV, SAY,
Le ee e

NEO

\ZN
ALES A TANANAN AVA 8 TAY ANSTANANAS
Xe WYYARABABAABABELALSA
AAV ANAV ANAVANAYAVANAS aay fees AY, ee LN AY AAVATAVAYANAUAVATAYA
AS ew OH fies OD COLO OOF OOH DOLE OOOOOO
BEE O XX O TaN XO * ees fe Oe A VANTIN
OK Z\ KK L\ a DOE OOK KK G
= SO fo may BOA OOO) REIS LED HOLE LEN
AEE SRR NE SRS Ease
ee wa COOOOee:
BEE OOOO? I\KININIWZS ES OOK Z\ ee Bees AAV AVX

LENGTH

HEIGHT

SMALL FIGURES ARE LENGTHS OF SPECIMENS {FROM SMOOTH CURVES)

VARIATIONS IN SHAPE OF INSTARS 107

D’Arcy THOMPSON’s GRAPHIC EXPRESSION OF GROWTH-GRADIENTS
APPLIED TO VALVES OF INSTARS

D’Arecy Thompson (1917, Chapter 17) devised an application of the
principle of Cartesian co-ordinates to the problem of animal form. A
rectangular grid of co-ordinates laid over the figure of an original form
can be enlarged and deformed to bear the same relationship to the figure
of the form in an advanced stage. The size and amount of this deformation
in any part of the grid is an index to the relative amount of growth.

Although the results may give a clear presentation of the growth-
gradients acting to change the shape of an organ or a species, they are
only qualitative. In a smooth outline, such as that of many ostracods,
there are no “guide points” to be followed through the various instars,
and this method of comparison offers a general pattern of the changes
which occur.

Figure 35 shows outlines of the instars centered on the lines of greatest
height and greatest length. Each of the outlines is based on average meas-
urements from all the specimens used in this study. Figure 36 shows the
graphic analysis of the growth pattern prepared according to the system of
D’Arcy Thompson. It can be seen that the dorsal anterior quadrant has
not grown as fast as the rest of the shell. We may say that its heterogony
(relative rate of growth as compared to the growth of the entire shell) is
negative, and that the value of the k in Huxley’s formula is less than 1.0
for this quadrant is positive throughout the development. The dorsal
posterior quadrant appears to be heterogonically negative through the
eighth instar, and changes abruptly in the final instar. It would also
appear that the heterogony of the ventral posterior quadrant is negative
through the fifth instar, but becomes positive in the later instars. As
we see in the following section, quantitative work on the same outline
drawings (Fig. 35) reveals that the graphic method gives false results
in some instances. Considerable caution is required in the evaluation of
D’Arey Thompson’s method, for it does not tell with certainty whether
the growth of any part is heterogonically positive (greater than the rest
of the body), isogonic (the same as the rest of the body), or heterogonic-
ally negative (slower than the rest of the body).

ScCHMALHAUSEN’S FORMULA APPLIED TO VALVES OF INSTARS

Schmalhausen (1927, p. 48; 1930, p. 294) has developed a formula for
the true growth-rate (G,) of an organ for a period of time from ¢ to ¢,
during which time the size of the organ increases from y to y,:

log y, — log y

Gy = 0.4343 Ca

Fic. 35. Average outlines of the various instars in lateral view, based on camera
lucida drawings of all specimens listed in Chart 1.

PILL]

ieeeog

=

LL/

Z
| TE
in:

Ea
ry

a

Fic. 36. D’Arey Thompson’s system of Cartesian co-ordinates applied to the
average outlines of instars shown in Fig. 35.
[ 108 ]

Chart 4

CHART 4

lOO PER CENT 3-FACTOR DIAGRAM

DISTANCE
SHOWING THE PERCENTAGES OF AVERAGE LENGTH, HEIGHT, AND

DISTANGE FROM ANTERIOR EDGE TO MAXIMUM HEIGHT FOR EACH KA
INSTAR STAGE, A

ars anten
wes MANDIBLE ae
wae waxieea

Be oe ss a

COO?
AX BARAK

i eee aia rope
ee Leo is rex DOO OOO?
ERE RS

VAN
IVAN
a ZAVAVAVAVAVAVAVAY,
VES
DIVVININA
Le Sl eee aL EA VAVAN,

VZ WA VV AAV ANAVAN ned
peas Bee ee
oO ( ees pee, A oe OM BOS oe raya aun

PAPA Nf
DD/VIN/SINISLYSLLBSES BOD
AVA WAVAVAVA KK oe DALY YZ

VAAAALAZ O12

BLLVN/ SA WAV ALLA

¥¥ Parana BALILALDILVLYVSLYLN YN
COO OOK

BOO WVAVAN KKK WALLA

—~

WAVAN
AX WAVAVAV, LVN 900) 0 OK

WAVAVAVAV A, DALY xX
KOO TRS mee OKA OOM

HEIGHT

VV O Oo a OO) VV/V\ AY Ot OO Ox
Oo ABR OREE ASAVANAT ANA oe BA

LENGTH

Mo Ms (by)

VARIATIONS IN SHAPE OF INSTARS 109

The true growth-rate of the body during the same period of time can
be similarly expressed:
log x, — logx

Co = 9 4343 (hee

The constant differential growth-ratio (k) is the ratio of these two

formulas:
G,__ log y, — log y

G, logx,— logs

This k is the same as the k in Huxley’s formula.’ This formula is based
on the total volume or weight, but it can also be applied to areas, since
the factor 24 in both numerator and denominator will cancel.

The area (in lateral view) of quadrants can therefore be compared
quantitatively with the area of the entire valve. Table 7 gives the values
of k for the quadrants of the ostracod valves, covering the growth in-

TABLE 7

Constant Differential Growth-Ratios by Quadrants.

Instar interval

Quadrant 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9
Dorsal anterior 0.66 0.87 0.89 0.90 0.93 0.87 0.84 0.95
Ventral anterior 0.99 1.07 1.08 1.07 1.06 1.05 1.31 1.25
Ventral posterior 1.22 1.17 1.10 1.08 1.07 1.04 1.16 0.96
Dorsal posterior 1.11 0.99 0.95 0.98 0.97 0.99 0.85 0.93

tervals from the first instar to the other instars in sequence. This statis-
tical treatment shows clearly that growth in any given instar is not con-
stant throughout the development, and that during any one interval the
growth varies from one quadrant to another. When we compare these
results with Thompson’s system of Cartesian co-ordinates, we see Imme-
diately that the numerical analysis has greater validity than the graphic
in evaluating growth.
* The transformation :

log y: = k log x, + (log yo — k log 20),
where yo is the size of the organ at its first appearance, and x, the corresponding
size of the rest of the body. Since (log yo — k log x.) will be a constant,
log y: = k log x, + log C
c= Car,

VII. Relation of Appendages and Internal

Organs to the Shape of the Valves in Instars

Each instar bears a definite relation to the preceding and the follow-
ing instars, since they are all only stages of the same amimal. The con-
tinuity of substance is accompanied by progressive changes of form.
Each part of an animal bears a definite relation to the other parts, and
the summation of these parts (the total animal) functions to carry on
those processes necessary for its survival in its environment ~— for if the
animal does not function successfully then the species cannot survive.

Since the carapace is the most important taxonomic structure of the os-
tracod, we are interested in any valid correlations between the shape of
the valves in the instars and the appendages and internal organs. A
mathematical comparison of the appendages and organs to the shell can
give a quantitative evaluation of the rates of growth which cannot be
attained by mere observation. However, any formula must be applied
with discretion.

Schmalhausen’s formula may be stated

_ log Yin +1) log Yn
~~ log x 1 — logz, ’

(m +

where n and n + 1 are successive instars, and k is the constant differen-
tial growth-ratio for the interval between them. As we have seen, this
formula can be applied to areas as well as volumes. It would be a
difficult task, subject to numerous errors, to determine the volume or
weight of an appendage in an ostracod. However, we can use a planimeter
to determine the areas of appendages and valves seen in lateral view,
provided all drawings are made to scale and each drawing is based on
a number of individuals to give average values. The errors of this method
are not sufficient to destroy its quantitative value.

Table 8 lists the computed values of the constant differential growth-
ratios of the appendages and portions of the valves. A complete analysis
of ostracod structure should also include the digestive system, the nervous
system, the glands, and connective tissues, but these were not measured
in sufficient cases to warrant their inclusion.

Study of the data in Table 8 has led the writer to believe that the
growth of individual appendages is relevant to the growth of the en-
closing portion of the valves. In general, the growth profile of the ap-

[110]

RELATION OF APPENDAGES AND ORGANS TO SHAPE OF VALVES 111

pendages and the rest of the body is directly reflected in the growth pro-
file of the valves. There is agreement of growth-ratios of appendages and
sections of the valves in individual instars, and there appears to be
concomitant variation of these two factors through the complete growth
cycle. Inasmuch as the ostracod apparently derives no external functional
advantage from the changes in shell shape, it may be assumed that such
changes bear some degree of relevance to internal structures. If this is
true, then our logic in seeking relationships between appendages and
valves is valid, and we have not committed a fallacy of cwm hoc ergo
propter hoc.

FIRST TO SECOND INSTAR

During this interval the greatest growth of an appendage occurs in the
mandible, which has changed from its pediform structure in the first
instar to its typical form. In the process of reorganization, the mandible
has moved from the middle of the posterior half of the valve toward the
anterior end; the 54-84 increment of the valve (from which the mandible
moved) has a growth-ratio of 0.89, while the 14%-%¢ increment (to which
the mandible shifted) has a growth-ratio of 1.10. The influence of the
mandible on the valve is also seen in the large growth-ratio of the pos-
teroventral quadrant. The maxilla appears as a small anlage in the second
instar; the value of k would therefore be infinity for this interval, but
such an interpretation is meaningless.

SECOND TO THIRD INSTAR

The antenna and the mandible show the greatest growth of the ap-
pendages. Both are shifted forward from their previous positions. This
agrees with the high ratios in the anterior half of the valve. The mawilla
and the small furea have low growth-ratios, and there is a corresponding
trend in the posterior half of the valve.

THIRD TO FourtTH INSTAR

The distribution of appendages in the fourth instar is somewhat dif-
ferent from that of the third. The position of the mouth has been shifted
forward so that the mandibular palp, the antenna, and the antennule are
now closer to the anterior end. The anterior one-fourth of the valve has
a low growth-rate, just as do the antennule and the antenna. The large
ratio in the 14-%% interval of the length corresponds to the forward shift
of the large mandibular palp and the base of the antenna. The maxilla
and the adjacent mid-sections of the valve have large growth-ratios.

It may be noted here that the growth-ratios for the increments inter-
cepted by intervals of the length do not always agree with the growth-
ratios of the quadrants of the valve. Chart 4 shows that the distance

112 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

TABLE 8

Constant Differential Growth-Ratios of Appendages and
Portions of the Valves of Instars.

Instar interval

Organ 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9
Antennule 1.05 0.52 0.16 0.98 0.68 1.05 0.70 2.33
Antenna 0.00 1.05 0.74 1.27 0.10 1.78 1.08 1.83
Mandible 2.07 1.52 0.26 1.66 0.17 1.17 1.13 2.18
Maxilla ve 0.48 1.25 1.15 0.65 1.40 1.35 1.90
Ist leg eae ar eae 3.81 0.00 0.89 0.84 1.92
2nd leg ees ae ee pee 3.61 0.56 1.89 2.23
3rd leg ec ate ae oh: eee 2.77 1.02 2.52
Fureca rere 0.23 1.08 —0.90 0.39 0.00 1.85 1.26

Increments of the Valve Intercepted by Intervals of the Length

Anterior

0-1/8 0.76 1.08 0.91 1.43 0.91 0.92 0.98 0.81
1/8-1/4 1.20 1.09 0.96 1.00 1.00 0.95 0.97 0.91
1/4-3/8 1.28 1.02 1.09 0.91 0.94 1.01 1.02 0.90
3/8-1/2 1.02 1.04 1.02 0.91 0.99 0.99 1.01 0.93
1/2-5/8 1.10 0.93 1.05 0.93 1.01 1.04 0.99 1.04
5/8-3/4 0.89 1.05 0.96 0.93 1.05 1.00 1.00 1.14
3/4-7/8 1.01 0.91 1.02 1.00 1.06 1.04 1.02 1.18
7/8-1 1.17 0.80 0.89 1.21 1.06 1.05 1.00 1.15
Posterior
Quadrant
Anterodorsal 0.66 0.93 1.01 0.96 1.01 1.03 1.14 1.05
Anteroventral 0.99 1.13 1.09 1.06 1.03 0.98 0.97 1.20
Posteroventral 1.22 1.13 0.98 1.02 1.04 0.93 0.91 0.79
Posterodorsal 1.11 0.89 0.89 1.05 0.94 1.05 0.98 1.00

from the anterior edge to the line of greatest height reaches its minimal
value in the third instar, and increases in all subsequent instars. This
means that a different proportion of the length is included in the an-
terior quadrants in each instar. Shght differences in the growth gradient
along the mid-dorsal edge can shift the apex of the valve forward or
back, and thereby influence the position of the dividing line between
the two anterior and the two posterior quadrants. Thus the increments
of the valve intercepted by intervals of the length offers a clearer picture
of growth changes in the valves than that offered by the quadrants.

FourtTH To FirtrH INSTAR

The first leg has an unusually high growth-ratio, and has assumed a
pediform structure in its endopodite in the fifth instar. On the other
hand, the furea actually decreases in size; this is the only negative
erowth-ratio encountered in the ostracod. The whole form of the furea
is changed, and the robust pediform structure of the fourth instar is re-

RELATION OF APPENDAGES AND ORGANS TO SHAPE OF VALVES 1S

placed with the delicate degenerate caudal appendage typical of the
Cypridopsinae. It seems to be more than coincidence that when the pedi-
form structure of the thoracic region is taken from one appendage (the
furca in this case) and transferred to another (the first leg), the former
has a low or even negative growth-ratio while its successor has a strong
counterbalancing growth-ratio. The same situation occurs in the follow-
ing growth interval where the second thoracic leg develops a pediform
structure at the expense of the first leg. This indicates that a pediform
structure is necessary for the thoracic region, and that the ostracod will
develop it at the expense of other appendages.

In this interval the strong growth of the antenna is reflected in the
large growth-ratio of the anterior portion of the valve.

The development of the first leg and the anlage of the second leg ex-
tends the length of the body toward the posterior end of the valve (see
Chart 4), where the growth-ratio is relatively large.

FIFTH TO SIXTH INSTAR

In this growth interval the second thoracic leg develops into a pedi-
form structure, while the palp of the first leg begins to lose its pediform
aspect. The increase of the thoracic pediform appendage again holds
true; the second thoracic leg has a large growth-ratio, while its predeces-
sor (the first leg) shows no growth during this interval.

The antennule, antenna, mandible, and maxilla are all located in the
anterior half of the valve. These appendages have low ratios, and so does
the anterior half of the valve.

The second thoracic leg is a large appendage and its large ratio is re-
flected in the ratios of the posterior half of the valve. The ratios of the
quadrants show also that the growth of the valve is centered in the
posteroventral region.

SIXTH TO SEVENTH INSTAR

In this interval all appendages are present. The third thoracic leg,
present as an anlage in the sixth instar, has a large growth-ratio.

The large ratios of the antenna and mandible have a corresponding
large ratio only in the 14-%¢ increment of the valve. The posterior half
of the valve has larger growth-ratios than the anterior half, probably
caused by the anlage of the ovary, which overshadows the growth pro-
file of the appendages.

SEVENTH TO EIGHTH INSTAR

The antenna, mandible, and maxilla show strong growth, as does the
4-38 and %-% increments of the valve.

114 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

The large ratios of the posterior half of the valve are probably related
jointly to the large increase of the large second thoracic leg and to the
anlage of the genital system.

EIGHTH TO NINTH INSTAR

All of the appendages show large growth-ratios as they assume the
robust character of the adult. The large growth of the posterior half of
the valve is related directly to the full development of the genital lobe.

Chart 5

HEIGHT ———>

EEE

CHART 5

Ma Ma (li)

CYPRIDOPSIS V/DUA INSTAR @

Ride)

AVERAGE

SHOWING

CYPRIDOPSIS VIDUA

SWZAZ Sy OF

THE

INSTAR 9 (Adult)

CYPRIS FASCIATA
INSTAR IF

OVERLAPPING OF

INSTAR

STAGES

LENGTHS

N

\
FSR

SA“

OF

AND

FOUR

HEIGHTS

SPECIES

[1ST Sha lola |e
TSESE TCI 4.
Bee HH
S55 ame
seuaan
SSG BB Pen
a
Bey 390
Sam
ET 300
on

7
z

Sec
NAT
EN

Q<
Pa

CYPRIDOPSIS VIDUA
INSTAR 3

CYPRINOTUS INCONGRUENS I]

SEeueuue

INSTAR 1

Ce

LENGTH ——>

40
$30 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 Be) S10 520 530 340 550 560 570

EEE EEE EEE EEE EE EEE

60 590 600 610 620 630 640 650 660

IX. Height-Length Ratio as a Valid Character

for Determination of Species

Height-length ratio has been used by various taxonomists as specific
character. They have supposed that a given height-length ratio is asso-
ciated with all instar stages of a species and they have assigned many of
the small ostracod valves of Paleozoic age to a particular species on the
basis of their having the proper height-length ratio.

It is a difficult process to draw all the boundaries of a living ostracod
species, where the appendages, the soft inner parts, and the fine details
of the shell are all present for examination. It seems unjustified to base
a classification on the ratio of two measurements in fossil forms, where
the appendages are absent and the shape of the valves is often distorted
in the process of burial and fossilization.

To test the dictum that the height-length ratio has specific significance,
the writer has compared the valves of living ostracods in which the
species are known to be definite by laboratory cultures. In a comparison
of species of Cypridae, the writer has found the ratio theory to be fal-
lacious in limitation of species. Chart 5 is based on the averages of the
instars of Cypris fasciata Miiller (averages from Claus 1868, p. 164;
figure constructed from description and figures of other instars of this
species), Cypris ovum Jurine (averages from Claus 1868, p. 164), and
Cyprinotus incongruens Ramdohr (averages and figures from Schreiber
1922) plotted on the same chart of height vs. length as Cypridopsis vidua
O. F. Miller. The dotted areas show the ranges of instars of C. vidua.
When the average heights and lengths of some instars of the other species
fall within the range of C. vidua, it is plausible that many of the indi-
vidual specimens of the different species have the same precise height and
length, and therefore, the same ratio. Even if two species did not have
the same height and length, the ratio of height to length could be the
same for individuals of both species.

An inspection of the figures shown in Chart 5 for comparison suggests
that an evaluation of factors other than height and length, such as the
distance from the anterior edge to the line of greatest height, would
serve to separate many of the individuals with duplicated height-length
ratios into their proper species.

However, it seems likely that if all possible diameters are compared
for specimens, some species will be found to have overlaps with others.

[115]

116 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

Using current techniques and measurements, it is probable that some of
the fossil smooth Cypridae are divided into “form species,” which contain
more than one actual species.

Ostracods can increase in importance as geologic indices only when new
criteria are found to improve the taxonomic classification. Since the
valves are the only parts preserved, except in rare instances, they should
be studied in greater detail in both living and fossil forms. The patterns
of muscle scars, particularly those in the dorsal area, may give additional
information. Such patterns are difficult to work out in living species, but
the value of the information promises to outweigh the time and effort
necessary for its achievement.

Bibliography

* The writer has not seen the originals of those references marked by an
asterisk.

ALEXANDER, C. I.
1933. Shell structure of the ostracods genus Cytheropteron, and fossil
species from the Cretaceous of Texas. Journal of Paleontology,
vol. 7, no. 7, pp. 181-214.
ALM, GUNNAR
1916. Monographie der Schwedischen Stisswasser-Ostracoden nebst sys-
tetnatischen Besprechungen der Tribus Podocopa. Zoologica Bidrag
fran Uppsala, vol. 4, pp. 1-248.
BAIRD, W.
1849. The natural history of the British Entomostraca. The Ray Society
London, 364 pp.
BERGOLD, ALFRED
1910. Beitrige zur Kenntnis des innern Baues der Siisswasserostracoden.
Zoologische Jahrbiicher, Abt. fiir Anat. und Ont. der Tiere, vol. 30,
pp. 1-42.
BERNECKER, A.
1909. Zur Histologie der Respirationsorgane bei Crustaceen. Zoologische
Jahrbiicher, Abt. fiir Anat. und Ont. der Tiere, vol. 27, pp. 583-
630.

BLOCHMANN, VON F.
1915. Das respiratorische Epithel bei Ostracoden. Zoologische Anzeiger,
vol. 45, no. 9, p. 391.
BRADLEY, P. C. SYLVESTER
1941. Shell structure of the Ostracoda. The Annals and Magazine of Nat-
ural History, 11th series, vol. 8, pp. 1-33.
BRADY, G. S.
* 1867. A synopsis of the recent British Ostracoda. Intellectual Observer,
vol. 12, pp. 110-130.
BRADY, G. S, and NORMAN, A. M.
* 1896. Monograph of the marine and fresh-water Ostracoda, sec. I. Trans.
Royal Dublin Soc., ser. 2, vol. 5.
BRADY, G. S., and ROBERTSON, D.
1870. The Ostracoda and Foraminifera of tidal rivers. The Annals and
Magazine of Natural History, ser. IV, vol. 6, pp. 1-33.
BRONNSTEIN, Z. S.
1924. Matenaly k Loznaniyu Ostracoda Moskovskoi Gubernii. Russ.
Hydrobiol. Zhurnal, vol. 3, pp. SO-88.
BRONNSTEIN, Z. 8S.
1925. Beitriige zur Kenntnis der Ostracodenfauna U.S.8.R. und Persiens.
Archiv fiir Naturgeschichte, vol. 91, no. 9, pp. 1-30.

[ 117 ]

118 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

CANNON, H.G.
1925. On the segmental excretory organs of certain fresh-water ostra-
cods. Philosophical Transactions of the Royal Society, London,
vol. 214, pp. 1-27.
CASPER, A.
1913. Die K6rperdecke und die Driisen von Dytiscus marginalis. Zeit-
sechrift fur wiss. Zool., vol. 107, pp. 387-509.
CHAMBERS, V. T.
1877. New Entomostraca from Colorado. Bull. U.S. Geol. and Geog.
Survey, vol. III, no. 1, Art. IV, p. 155.
CHYZER, C.
1858. Uber die Crustaceen-fauna Ungarns. Verhandl. der k. k. Zoolog.-
botan. Gesellschaft in Wien, pp. 505-518.
CLARK, G. L., and SMITH, A. F.
1936. X-ray diffraction studies of chitin, chitosan, and derivatives. Jour-
nal of Physical Chemistry, vol. 40, no. 7, pp. 863-879.
CLAUS, CARL
1868. Beitrage zur Kenntnis der Ostracoden. I. Entwicklungsgeschichte
von Cypris. Schr. Ges. ges. Naturw., Marburg, vol. 9, pp. 151-166.
1893. Beitrige zur Kenntnis der Susswasser-Ostracoden, I. Uber den
Korper- und Ghedmassenbau der Cypriden. Arb. zool. Inst. Wien,
vol. 10, pp. 147-216.
1895. Beitrige zur Kenntnis der Stisswasser-Ostracoden, II. Arb. zool.
Inst. Wien, vol. 11, pp. 17-48.
CUSHMAN, JOSEPH A.
1907. Ostracoda from southeastern Massachusetts. American Naturalist,
vol. 41, pp. 35-39.
DADAY, E. VON
1905. Untersuchung uber die Stsswasser-Mikrofauna Paraguays. Zoo-
logica (Stuttgart), vol. 44, pp. 1-374.
DEBAISIEUX, PAUL
1944. Les Yeux de Crustacés. La Cellule, Tome 50, Fase. 1, pp. 1-122.
DOBBIN, CATHERINE N.
1941. Fresh-water Ostracoda from Washington and other western lo-
ealities. Univ. Washington Pub. in Biology, vol. 4, pp. 174-246.
DUDICH, E.
1929. Die Kalkeinlagerungen des Crustaceenpanzers in polarisierten Licht.
Zoologische Anzeiger, vol. 85, pp. 257-264.
EDWARDS, H. MILNE
1857. Lecons sur la Physiologie et l’Anatomie Comparée, vol. 2. Paris.
FASSBINDER, K.
1912. Beitrige zur Kenntnis der Stsswasserostracoden. Zoologische Jahr-
bicher, Abt. fir Anat. und Ont. der Tiere, vol. 32, pp. 533-576.
FERGUSON, EDWARD
1944. Studies of the seasonal life history of three species of fresh-water
Ostracods. The American Midland Naturalist, vol. 32, no. 38, pp.
713-727.
FOREL, F. A.
1883. Die pelagische Fauna der Stisswasserseen. Biologische Zentralblatt.,
Jahrgang II, pp. 299-305.

BIBLIOGRAPHY 119

FOWLER, G. H.
1909. The Ostracoda. Biscavan Plankton, Part XII. Transactions of the
Linnean Society, Zoology, vol. 10, part 9, pp. 219-336.
FOWLER, HENRY W.
1912. The Crustacea of New Jersey. Annual Report New Jersey Museum,
1911, pp. 29-651.
FRANZ, V.
1910. Photoaxis und Wanderung. Internationale Revue der gesammte
Hydrobiol. u. Hydrog., vol. 3, pp. 306-334.
FRIC, ANTON
1872. Die Krustenthiere Bohmens. Archiv der Naturwissenschaftliche
Landesdurchforschung von Bohmen, Arbeiten der zoologischen Sec-
tion, vol. 2, no. 4, pp. 206-296.
FURTOS, NORMAN C.
1933. The Ostracoda of Ohio. Ohio Biological Survey, vol. 5, pp. 411-524.
1936. Fresh-water Ostracoda from Florida and North Carolina. American
Midland Naturalist, vol. 17, pp. 491-522.
GARBINI, ADRIANO
1887. Contribuzione all’ anatomie ed alla istologia delle Cypridinae.
Bulletino della Societa Entomologica Italiana, Firenze, vol. 19, pp.
35-51.
GAUTHIER, HENRI
1939. Sur la Structure de la Coquille Chez Quelques Cypridopsides a
Furca Réduite et Sur la Validité du Genre Cyprilla (Ostracodes).
Bull. de la Soc. Zool. de France, vol. 64, pp. 203-228.
GIBSON, R. E., WYCKOFF, H. W. C., and MERWIN, H. E.
1925. Vaterite and p-calcium carbonate. American Journal of Science,
vol. 210, pp. 325-333.
GRAF, HERBERT
1940. Zur Kenntnis der ostalpinen Muschelkrebs Fauna. Archiv fiir
Hydrobiol., vol. 36, pp. 483-490.
HANSTROM, BERTIL
1924. Beitrag sur Kenntnis des zentralen Nervensystems der Ostracoden
und Copepoden. Zoologische Anzeiger, vol. 61, pp. 31-38.
1928. Vergleichende Anatomie des Nervensystems der wirbellosen Tiere
unter Berucksichtigung seiner Funktion. Berlin.
1929. Das Deutocerebrum der Crustaceen. Zoologische Jahrbiicher, Abt.
fur Anat. und Ont., vol. 51, pp. 535-549.
1933. Neue Untersuchungen iiber Sinnesorgane und Nervensystem der
Crustaceen II. Zoologische Jahrbiicher, Abt. fiir Anat. und Ont.,
vol. 56, pp. 887-517.
1934. Neue Untersuchungen tiber Sinnesorgane und Nervensystem der
Crustaceen III. Zoologische Jahrbiicher, Abt. fiir Anat. und Ont.,
vol. 58, pp. 101-144.
HANSEN, H. J.
1893a. A contribution to the morphology of the limbs and mouth parts of
Crustaceans and insects. Annals and Magazine of Natural His-
tory, ser. 6, vol. 12, pp. 417-434.

120 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

1893b. Zur Morphologie der Ghedmassen und Mundtheile bei Crustaceen
und Insekten. Zoologische Anzeiger, vol. 16, pp. 193-198, 201-212.
1905. Two new forms of Choniostomatidae: Copepoda parasitic on
crustacea Malacostraca and Ostracoda. Quarterly Journal of Micro-
scopic Science, vol. 48, pp. 354-375.
HARTWIG, W.
1901. Uber das Sammeln, Auslesen und Konservieren der Ostracoden.
Sitzungsberichte der Gesellschaft Naturforschender Freund zu Ber-
lin, 1901, pp. 11-14.
HARVEY, E. NEWTON
1917. Studies in Bioluminescence, IV. The chemistry of light production
on a Japanese ostracod Crustacean, Cypridina Hilgendorfi Miiller.
American Journal of Physiology, vol. 42, pp. 318-348.
HEIDE, FRITZ
1924. Uber den Vaterit. Zentralblatt fiir Mineralogie, Geologie, und Pale-
ontologie, Jahrgang, 1924, pp. 641-651.
HERR, 0.
1921. Hydrobiologische Beobachtungen aus dem _ Riesengebirge. Zool-
ogische Anzeiger, vol. 53, pp. 12-16.
HERRICK, C. L.
1887. Contribution to the fauna of the Gulf of Mexico and the South.
Memoirs of the Denison Scientific Association, vol. 1, no. 1, pp. 1-46.
HIRSCH MANN, NIKOLAJ
1912. Beitrag zur Kenntnis der Ostrakodenfauna des Finnischen Meer-
busens. Acta Soc. Fauna Flora Fennica, vol. 36, no. 2, pp. 1-66.
HOEVEN, J. VAN DER
1856. Handook of zoology. Translation by W. Clark, London.
HOFF, C. C.
1942a. The ostracods of Illinois, their biology and taxonomy. Illinois
Biological Monographs, vol. 19, nos. 1-2, pp. 1-196.
1942b. The subfamily Entocytherinae, a new subfamily of fresh-water
Cytherid Ostracoda, with descriptions of two new species of the
genus Entocythere. American Midland Naturalist, vol. 27, pp.
63-73.
1943a. The Cladocera and Ostracoda of Reelfoot Lake. Journal of the
Tennessee Academy of Science, vol. 18, pp. 49-107.
1943b. Seasonal changes in the ostracod fauna of temporary ponds. Ec-
ology, vol. 24, pp. 116-118.
1944. The origin of Nearctic fresh-water ostracods. Ecology, vol. 25, pp.
369-372.
HOLMES, A.
1937. Ostracods of Lake Ohrid (Jugoslavia-Albania). Archiv fiir Hydro-
biologie, vol. 31, pp. 484-499.
HUXLEY, J. 8.
1924. Constant differential growth-ratios and their significance. Nature,
vol. 114, p. 895.
1932. Problems of relative growth, Methuen & Co., Ltd., London.
JOHANSEN, FRITZ
1921. The larger fresh-water crustacea from Canada and Alaska. The
Canadian Field-Naturalist, vol. 35, pp. S8-94.

BIBLIOGRAPHY 121

JOHNSTON, J., MERWIN, S. E. and WILLIAMSON, M. D.
1916. The several forms of calcium carbonate. American Journal of
Science, vol. 191, pp. 478-513.
JURINE, LOUIS
* 1820. Historie des Monocles, qui se trouvent aux environs de Geneve.
Geneve.
KAUFMANN, A.

1900a. Zur Systematik der Cypriden. Mitt. naturf. Ges. Bern, pp. 103-
109.

1900b. Cypriden und Darwinulidae der Schweiz. Revue Suisse Zoologie,
vol. 8, pp. 209-423.

1900ce. Neue Ostracoden aus der Schweiz. Zoologische Anzeiger, vol. 28,
pp. 131-155.

KIERNICK, EB.

1908. Uber einige bisher unbekannte leuchtende Thiere. Zoologische An-

zeiger, vol. 33, pp. 376-880.
KLIE, WALTHER

1926. Ostracods. Biologie die Tiere Deutschlands, vol. 22, pp. 1-56.

1931. Zwei neue Arten der Ostracoden-Gattung Candona aus unterird-
ischen Gewissern im siidéstlchen Europa. Zoologische Anzeiger,
vol. 96, pp. 161-168.

1934. Zwei neue subterrane Ostracoden der Gattung Candona. Zoologische
Anzeiger, vol. 106, pp. 198-199.

1936. Neue Candoninae aus dem Grundwasser von Belgien. Bulletin Mu-
seum Historie Naturelle Belgique, vol. 12, no. 15, pp. 1-15.

1938a. Ostracoda, Muschelkrebse. Die Tierwelt Deutschlands und der
Anerensenden Meersteile, vol. 34, pp. 1-250.

1938b. Sphaeromicola dudichi n. sp. (Ost.), ein Kommensale des Boh-
ramphipoden Chelura terebrans. Zoologische Anzeiger, vol. 121, pp.
317-322.

1940. Siisswasserostracoden aus Nordostbrasilien. Zoologische Anzeiger,
vol. 130, pp. 59-72.

KLUGH, A. B.

1921. Notes on Canadian Entomostraca. Canadian Field Naturalist, vol.
30, pp. 72-73.

1927. The ecology, food relations and culture of fresh-water Entomos-
traca. Trans. Royal Canadian Institute, vol. 16, pp. 15-99.

KOFOID, C. L.

1908. Plankton Studies. V. The plankton of the Illinois river, 1894-1899.
Part Il. Constituent organisms and their seasonal distribution.
Bulletin Ulinois Laboratory Natural History, vol. 8, pp. 1-361.

KORSCHELT, E.

1914. Uber das Verhalten verschiedener wirbelloser Tiere gegen niedere
Temperaturen. Zoologisch Anziger, vol. 45, pp. 106-120.

1920. Lebensdauer und Altern bei Copepoden und Ostracoden (nach
Untersuchungen von Dr. E. Walter und Dr. E. Schreiber). Sit-
zungsberichte der Gesellschaft zur beforderung der gesammten
naturwissenschaften zu Marburg, 1920, pp. 67-75.

LATREILLE, P. A.

1802. Histoire naturelle, générale, et particuliére des Crustacés et des In-

sects, vol. 3. Paris.

122 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

LIENENKLAUS, E.
1900. Die tertiir-Ostrakoden des Mittleren Norddeutschlands. Zeitschr.
der deutsch. geol. Gesell., vol. 52, pp. 497-550.
LOWNDES, A. G.
1934. Inheritance in fresh-water ostracods. Nature, vol. 133, p. 873.
1935. The sperms of fresh-water ostracods. Proceedings of the Zoological
Society of London, 1935, Part 1, pp. 35-48.
LOEB, J.
1890. Weitere Untersuchungen iiber den Heliotropismus der Thiere und
seine Ubereinstimmung mit dem Helhotropismus der Pflanzen.
Archiv fiir ges. Physiologie, vol. 47, pp. 391-416.
LUDERS, LEO
1909. Gigantocypris agassizi (Miiller). Zeitrschrift fiir wissenschaftlichen
Zoologie, vol. 92, pp. 105-148.
MANN, H., and PIEPLOW, U.
1938. Der Kalkhaushalt bei der Hiutung der Krebse. Sitzungsberichte der
Gesellschaft Naturforschender Freunde zu Berlin, Jahrgang 1938,
no.Lopp. 141%,
MARSHALL, W. S.
1903. Entocythere cambaria nov. gen. et nov. spec., a parasitic ostracod.
Transactions of the Wisconsin Academy of Science, vol. 14, pp.
117-144.
MASI, LUIGI
1909. Deserizione di aleune Cypridae itahane. Archivo Zoologico (Na-
poli), vol. 3, pp. 347-407.
MEYER, K. H., and MARK, H.
1928. Uber den Aufbau des Chitins. Berichte der Deutschen Chemischen
Gesellschaft, vol. 61, pp. 1936-1939.
MEYER, K. H., and PANKOW, G. W.
1935. Sur la constitution et la structure de la chitine. Helvetica Chimica
Acta, vol. 18, pp. 589-598.
MCNOD, TH.
1932. Uber drei indopazifisehe Cypridiniden und zwei in Ostracoden
lebende Krebstiere. Zoologische Anzeiger, vol. 98, pp. 1-8.
MRAZEK, AL
1890. O eysticerkoidech nasich Korysu sladkovodnich. Prispévek k. bio-
logit a morfologil cestodu. Sitzungsberichte der k. Bohmischen
Gesellschaft der Wissenschaften, pp. 226-248.
MULLER, G. W.
1889. Die Spermatogenese der Ostracoden. Zoologische Jahrbiicher, Abt.
fiir Anat. und Ont. der Tiere, vol. 3, pp. 677-726.
1890. Neue Cypriden. Zoologische Jahrbiicher, Abt. Syst. Geog. und Biol.,
vol. 5, pp. 211-252.
1894. Die Ostracoden des Golfes von Neapal und der angrenzenden
Meeressbschnitte. Fauna und Flora des Golfes von Neapal, Mono-
graph 21.
1898. Die Ostracoden. Sonderabdruck aus den Abhandlungen der Sencken-
bergischen naturforschenden Gesellschaft, vol. 21, no. 2, pp. 257-
259.
1900. Deutschlands Stisswasser Ostracoden, Zoologica, (Stuttgurt), No.
30, pp. 1-112.
1912. Ostracoda, Das Tierreich, vol. 31, pp. 1-454.

BIBLIOGRAPHY 123

MULLER, O. F.
* 1776. Zool. Danicae Prodomus. Havniae.
* 1785. Entomostraca seu Insecta testacea, quae in aquis Daniae et Nor-
veglae reperit, descripsit et iconibus illustravit. Lipsiae et Hawniae.
MULLER, WILHELM
1880. Beitrag zur Kenntnis der Fortpflanzung und der Geschlechtsver-
haltnisse der Ostracoden. Zeitschr. ges. Naturw., vol. 53, pp. 221-
246.
MULLER-CALE, K.
1913. Uber die Entwicklung von Cypris incongruens. Zoologische Jahr-
bicher, Abt. fir Anat. und Ont., vol. 36, pp. 113-170.
NORDQUIST, 0.
1885. Beitrag zur Kenntnis der inneren minnlichen Geschlechtsorgane der
Cypriden. Acta Soc. Sei. Fenn., vol. 15, pp. 1-41.
NORMAN, A. M., and SCOTT, T.
1906. The Crustacea of Devon and Cornwall. Wesley & Son, London.
NOWIKOFF, M.
1908. Uber den Bau des Medianauges der Ostracoden. Zeitschrift fiir wis-
senschaftliche Zoologie, vol. 91, pp. 81-92.
OKADA, YO K.
1926. Luminescence et Organe Photogene des Ostracodes. Bull. de la Soe.
Zool. de France, vol. 51, pp. 478-486.
OSTWALD, W.
1907. Zur Theorie der Richtungsbewegungen niederer schwimmender
Organismen. III. Uber die Abhingigkeit gewisser heliotropischer
Reaktionen von der inneren Reibung des Mediums sowie iiber die
Wirkung “mechanischer Sensibilisatoren.” Archiv fiir gesammete
Physiologie, vol. 117, pp. 384-408.
RADL, E.
1901. Uber der Phototropismus einiger Arthropoden. Bio'ogisches Zen-
tralblatt, vol. 21, pp. 75-86.
RAMSCH, ALFRED
1906. Die Weiblichen Geschlechtsorgane von Cypridina mediterranea
Costa. Arb. zool. Inst. Wien, vol. 16, pp. 383-398.
RAWSON, DONALD 8.
1930. The bottom fauna of Lake Simcoe (Ontario) and its role in the
ecology of the lake. Univ. Toronto Stud. Biol., vol. 34, pp. 1-183.
REDEKE, H. C., and DULK, A. DEN
1940. Ostracoda of the Netherlands. Archives Néerlandaises de Zoologie,
vol. 4, pp. 189-148.
REED, G. B., and KLUGH, A. B.
1924. The correlation between hydrogen ion concentration and the biota
of granite and limestone pools. Ecology, vol. 5, pp. 272-275.
RETZIUS, GUSTAV
1909. Die Spermien der Ostracoden. Biologische Unterschungen, Neue
Folge, vol. 14, pp. 5-14.
RICHARD, J.
1896. Note sur un Limnicythere du Bois de Boulogne. Bull. Soc. Zool. de
France, vol. 21, p. 173.
ROBBINS, BRODY, HOGAN, JACKSON, and GREENE
1928. Growth. Yale University Press, New Haven, Connecticut.

124 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

ROIJA, E.

1942. Description de una especia y una subspecie neuvas del genero
Entocythere Marshall procedentes de la cueva chica. Ciéneia, vol. 3,
pp. 201-204.

ROME, DOM REMACLE

1947. Herpetocypris reptans, I. Morphologie Externe et Systeme Nerveux.

La Cellule, vol. 51, pp. 51-152.
RUTTNER, F.

1914. Bemerkungen zur Frage der vertikalen Planktonwanderung. Inter-
nationale Revue der gesammte Hydrobiol. u. Hydrog., Biol. Sup.,
pp. 1-12.

SARS, G. 0.

1889. On some fresh-water Ostracoda and Copepoda, raised from dried
Australia mud. Forhandlinger 1. Videnskabs-Selskabet 1 Christiania,
pp. 1-79.

1890. Oversigt af Norges Crustaceen, med forelobige Bemaerkninger over
die nye eller mindre bekjendte Arter. Forhandlinger 1. Videnskabs-
Selskabet 1 Christiania, pp. 1-80.

* 1895. On some South-African Entomostraca raised from dried mud. Chris-
tian. Selsk. Skr. I. Math.-nat. Kl., no. 8, pp. 1-56.

* 1896. On some West Australian Entomostraca raised from dried mud.
Archiv. Math. Naturv., vol. 19, no. 1, pp. 1-385.

1901. Contributions to the knowledge of the fresh-water Entomostraca of
South America as shown by hatching from dried material. Archiv
Math. Naturv., vol. 24, no. 1, pp. 1-52.

SAWAYA, PAULO

1942. Contribuicao para a fisiologia do aparelho de apreencao dos alimen-
tos e la glandula do intestino médio do Ostracodo. Acao de substan-
cias colinérgicas. Universidade de Sao Paulo, Boletin de Fauculdade
de Filosofia, Ciéneias e Letras, Zool., vol. 25, no. 6, pp. 107-147.

SCHEERER-OSTERMEYER, ELSE

1940. Beitrag mur Entwicklungageschichte der Stsswasserostrakoden.
Zoologische Jahrbiicher, Abt. fiir Anat. und Ont. der Tiere, vol.
66, pp. 349-370.

SCHLIEP, W.

1909. Vergleichende Untersuchung der Eireifung bei parthenogenetrisch
und bei geschlechtlich sich fortpflanzenden Ostracoden. Archiv fur
Zellforschung, vol. 2, pp. 390-431.

SCHMALHAUSEN, J.

1927. Beitriige zur quantitativen Analyse der Formbildung. IT. Das Prob-
lem des proportionalen Wachstums. Archiv der Entw. Mech., vol.
110, pp. 33-62.

1930. Uber Wachstumformeln und Wachstumstheorien. Biologische Zen-
tralblatt, vol. 50, pp. 292-307.

SCH MALZ, JOSEF

1912. Zur Kenntnis der Spermatogenese der Ostracoden. Archiv fur Zell-

forschung, vol. 8, pp. 407-441.
SCHREIBER, ERNA

1922. Beitriige zur Kenntnis der Morphologie, Entwicklung und Lebens-
weise der Siisswasser-Ostracoden. Zoologische Jahrbiicher, Abt.
fir Anat. und Ont. der Tiere, vol. 45, pp. 485-539.

BIBLIOGRAPHY t25

SCOTT, HAROLD W.
1944, Permian and Pennsylvanian fresh-water Ostracodes. Journal of
Paleontology, vol. 18, no. 2, pp. 141-147.
SHARPE, R. W.
1897. Contribution to a knowledge of the North American fresh-water
Ostracoda included in the families Cytheridae and Cypridae. Bull.
Illinois Laboratory Natural History, vol. 4, pp. 414-482.
1903. Report on the fresh-water Ostracoda of the United States National
Museum, including a revision of the sub-families and genera of the
family Cyprididae. Proc. U. 8. Museum, vol. 26, pp. 969-1001.
1918. The Ostracoda. Ward and Whipple, Fresh Water Biology, pp. 790-
827.
SKOGSBERG, TAGE
1920. Studies on marine ostracods. Zoologiska Bidrag fran Uppsala, Sup-
plement 1, pp. 1-754.
SPANDL, HERMAN
1925. Die Tierwelt voriibergehenden Gewisser Mitteleuropas. Archiv fur
Hydrobiol., vol. 16, pp. 74-152.
STRAUS, H. E.
1821. Mémoire sur les Cypris, de la classe des Crustacés. Mem. Mus.
d’Hist. Nat., vol. 7, Paris.
STUHLMANN, F.
1886. Beitrage zur Anatomie der inneren minnlichen Geschlechtsorgane
und zur Spermatogenese der Cypriden. Zeitschrift fiir wissensch.
Zool., vol. 44, pp. 536-569.
THIENEMANN, AUGUST
1912. Die Faktoren welche die Verbreitung der Stisswasserorganismen
regeln. Archiv fiir Hydrobiol., vol. 8, pp. 267-288.
THOMPSON, D’ARCY W.
1917. Growth and Form. Cambridge University Press, 793 pp.
TOWLE, ELIZABETH W.
1900. A study of the heliotropism of Cypridopsis. American Journal of
Physiology, vol. 38, no. 8, pp. 545-365.
TURNER, C. H.
1895. Fresh-water Ostracoda of the United States. Second Report of the
State Zoologist of Minnesota, pp. 277-3837.
1896. Morphology of the nervous system of Cypris. Journal of Compara-
tive Neurology, vol. 6, pp. 20-44.
1899. Synopsis of North-American Invertebrates, V. Fresh-water Ostra-
coda. American Naturalist, vol. 35, pp. 877-888.
UNDERWOOD, LUCIEN M.
1886. List of the described species of fresh water crustacea from America
north of Mexico. Bull. Hlinois Laboratory of Natural History, vol.
2, pp. 323-386.
VAVRA, V.
1891. Monographie der Ostracoden Bohmens. Archiv nat. Landesdurch-
forschung Bo6hmens, vol. 8, pp. 1-116.
1909. Ostracoda, Muschelkrebse. Brauer, Die Siisswasserfauna Deutsch-
lands, vol. 11, no. 2, pp. 85-136.

126 THE MORPHOLOGY OF OSTRACOD MOLT STAGES

WARD, HELEN L.
1940. Studies on the life history of Neoechinorhynchus cylindratus (Van
Cleave, 1915). Transactions of American Microscopical Society,
vol. 59, pp. 327-347.
WEBER, MAX
1879. Uber den Bau und die Thitigkeit der sogenannten Leber der Crus-
tacean. Archiv fur Mikrosk. und Anatomie, vol. 17, pp. 385-457.
WECKEL, ADA L.
1914. Free-swimming fresh-water Entomostraca of North America. Trans-
actions of American Microscopical Society, vol. 35, pp. 164-203.
WEISMANN, A.
1880. Parthogenese bei den Ostracoden. Zoologische Anzeiger, vol. 3, pp.
82-84.
WEISMANN, A., and ISHIKAWA, C.
1888S. Uber die Bildung der Richtungskorper bei thierischen Eiern. Ber-
ichte der naturforschenden Gesellschaft zu Freiburg, vol. 3, pp. 1-
44.
WILSON, EDMUND B.
1925. The cell in development and heredity. Third edition, the MacMil-
lan Company, New York.
WOHLGEMUTH, R.
1914. Beobachtungen und Untersuchungen iiber die Biologie der Siiss-
wasserostracoden; ihr Vorkommen in Sachsen und Boéhmen, ihre
Lebensweise und ihre Fortpflanzung. Internationale Revue der Hy-
drobiol., Biol. Supp., vol. 6, pp. 1-72.
WOLF, JOHANN P.
1919. Die Ostracoden der Umgebung von Basel. Archiv fiir Naturges-
chichte, Abt. A., vol. 85, no. 3, pp. 1-100.
WOLTERECK, RICHARD
1S98. Zur Bildung und Entwickling des Ostrakoden-Eies. Zeitschrift fiir
wissenschaftlichen Zoologie, vol. 64, pp. 596-623.
YATSU, NAOHIDE ,
1917. Note on the structure of the maxillary gland of Cypridina Hilgen-
dorfu. Journal of Morphology, vol. 29, pp. 485-439.
YERKES, R. M.
1899. Reactions of Entomostraca to stimulation by light. American Jour-
nal of Physiology, vol. 3, pp. 157-182.
1900. Reactions of Entomostraca. 2. Reactions of Daphnia and Cypris.
American Journal of Physiology, vol. 4, pp. 405-422.
ZADDACH, E. G.
* 1844. Synopseos Crustaceorum Prussicorum Prodromus. Dissertatio zool-
ogica. Regiomonti (Konigsberg).
ZENKER, W.
1854. Monographie der Ostrakoden. Wiegmann’s Archiv fiir Naturges-
chichte, vol. 20, pp. 1-87.
ZSCHORN, JOHANNES
1937. Beitrige zur Skelettbildung bei Arthropoden. Zoologische Jahr-
bucher, Abt. fiir Anat. und Ont., vol. 62, pp. 323-348.

Plates

Plate 1

Nos. 1-4. Adult Cypridopsis vidua O. F. Miller, 10 frontal sections, stained
with Ehrhch’s haematoxylin and eosin. The sections progress from the dorsal area
to the ventral.

| 128 |

PLATE |

chitin coating
of the hypodermis

anterior overlap eye excretory giond 8

longitudinal
muscles
of the gut

stomach

i@) antennule

rear soc of ganglion of the

100 excretory gland 8 oa! : antenatie

200 4 4
r< =i) ¥ \ ‘ liver

liver a, eo Te | secretion

food ball : SZ

egg
uterus
rear gut

S\N

epidermal cells

[ 129 ]

Plate 2
Nos. 5-8. Adult, 10 frontal sections. These sections follow those shown in
Plate 1.

1 130 ]

PLATE 2

chitin coating
of the hypodermis

ontennule

rear sac of orifice of oe lining
excretory rear sac 9 e
gland 8

hypodermis

stomach ge Mer
nucleus
uterus of egg
ve be Pe 2
x N, #4
subdermal ‘\ ; <
cell «* .
\ ye fo
5 all i subdermai
5 «fF ff = pet ” j cells
1g x 6 .
anterior
overlap
body wall
forehead epidermal
cells
~
end sac of ’
excretory
gland 8 \
\
} closing
i muscles
food ball ‘
ovary
egg

»=—— epidermal
cells

[131 J

Plate 3

Nos. 9-12. Adult, 10u frontal sections. These sections follow those shown in
Plate 2.

1 132 |

anterior overlap

—_———

epidermal
cells

forehead

excretory
gland B

dorsal Wulst

closing
muscles

liver
seminal

receptacle | 4 ~ a
‘© long! ae . liver
\, #e soi: ed P
;

£99

ovary

ovary

antennule —

antennae

antenna —__ cerebrum

N
orifice of gland

excretory

glond A (y » :

excretory
gland A

closing
muscles
third
thoracic
leg
excretory ging
gland ©
; =
, opening ~ ed
ay of uterus “wy J 2§
spiral ee gi 2
canals s y oe
11 ; “ °

[2 Me hte

Plate 4

Nos. 13-16. Adult, 10 frontal sections. These sections follow those shown in
Plate 3.

[ 134 ]

PLATE 4

anterior
overiap

cerebrum enjeang

excretory
glond &

closing

excretory
muscles

gland G

liver liver Siang 6
gland O
spiral
canal
spiral . i }
canal Pug / “genital
lobe
ef
ovary
chitin coating
of the hypodermis epidermal
calls cerebrum

chitin lining
of the
hypodermis

endoskeleton

esophagus
—gland N
branchial ‘
plate of
maxilte :
opening
of vagina
oes ~ body wold
thoracic
leg muscles
opening
of uterus
furco —— ovary

ol i y wy > ‘a Sag
5 <¥ vk 16 Nw “a

[ 135 ]

Plate 5

Nos.17-20. Adult, 10u frontal sections. These sections follow those shown in
Plate 4.

[ 136 ]

PEATE. 5

£ aa >. epidermol cells
‘

pharynx

antenna muscies
endoskeleton
mandible
branchial
plate of gland N_
o4ille maxiila
ventral chain Pi ¢
f ganglia :
of gang leg
spiral
canal second
thoracic
genital leg
jobe ‘ { :
‘ ; a,
is Ve &] ovary
i
upper lip
esophagus gland L re
branchial mandible
piote
_ maxilla
gland N —
first
thoracic
leg
second
thoracic

leg

| 137 ]

Plate 6

Nos. 21-24. Adult, 10, frontal sections. These sections follow those shown in
Plate 5.

[ 138 ]

PLATE 6

antennae

uoper flip
mondibulor i
polp giond L
; mandible
exopodite a
mandibulor
palo

maxitia _____—._ hypostome

: maxilla
first
thoracic first
leg thorocic
leg
second
thorocic
leg
% \ 0
; --ic0
aoe
we Pee L—- 2O0
antenna ff 4% ~
Pe he, —
‘ |
mandibulor '
alp pate
Z . glond M
mandible —
maxilla
moxilio ——~—=~_ hy postome
exopodite
plate of
first fea
first
theracic
leg

[ 139 ]

Plate 7

Nos. 25-28. Adult, 10 frontal sections. These sections follow those shown in
Plate 6, and reach to the ventral border of the shell.

Nos. 29-54. Adult, 10u sagittal sections, stained with Ehrlich’s haematoxylin
and eosin. The sections progress from the left to the right side.

[ 140 ]

PLATE .-7

ay
§
:
i
a) maxillery
y setae
upper lip y
‘= | :
otrium ‘ 4 eA

chitin coating

of hypodermis 4
SS $ i

Ne
a
We.
ao

25 a "

6
POOP I 5 ae
*
A,

0 100 200. x
ee 30 31

chitin =
coating 4 epidermal
: mR —icelis

do at
a }
Closing
muscles ~~.
yentrol closing ~
muscles si liver
er epidermal
“ae
cells
od
\ £ '
&
%
aw \

[ 141 ]

Plate §

Nos. 35-40. Adult, 10u sagittal sections. These sections follow those shown in
Plate 7.

[ 142 ]

PLATE 8

chitin coating
of the
hypodermis

closing
muscles

liver

od 36

giand B
3 ; 5 conal

end soc ‘ a from liver
NG ga A rear ede to stomach

closing
muscles chitin
lining

egg
epidermal

cells
branchial
* plate of
< chitin maxilla
cooting

40

[ 143 ]

Plate 9

Nos. 41-46. Adult, 10m sagittal sections. These sections follow those shown in
Plate 8.

[ 144]

PLATE 9

chitin

lining conal
from liver chitin
to stomach coating

uterus

ovary

ai ‘as® 4g Ne 43

antennule
antenna

eye : p-eye

: ‘ stomach
maxilla

excretory
gland A

bronchial %
plote

j spiral

j canals

~~ bronchial
plate

nucleus

[ 145 ]

Plate 10

Nos. 47-52. Adult, 10u sagittal sections. These sections follow those shown in
Plate 9.

| 146 |

fics ann % ontennule

stomach

rear

awe y
ae “seminal
receptacle
spiral. circular
canal muscles
oN rear
, NS gut
\ 48 49 \
47 onus
\
pharynx muscle
d i un esophagus
Wulst Watst \ eee MD cerebrum
" \ \ ‘ forehead
: < cerebrum \ upper \ VAS orehead
: ips e/. ZX

_ofrium

“hypostome

jpeow

Nephi

stomach

genital
lobe

gland O

oer S| 52. MINES

[ 147 ]

Plate 11

Nos. 53-58. Adult, 10u sagittal sections. These sections follow those shown in
Plate 10.

[ 148 ]

ventral
chain of
ganglia |

opening

uterine

opening £9q

furca

epidermal
cells

upper
lip

56

) endoskeleton

excretory

endoskeleton gland A

nucleus

54

conal
from liver
to stomach

spiral

epidermal
cells

ovary

[ 149 ]

Plate 12

Nos. 59-64. Adult, 10u sagittal sections. These sections follow those shown in
Plate 11, and conclude the sequence which began on Plate 7, No. 29.

| 150 |

PLATE (2

- 2 0
a , a
. | Ss
aD ’ ‘
: ay : . ~
m ; ~ ie “i
in maxille a ay : i, \ mandibular
a fe ee palp
ss : mandible ‘ oe

S74

WEF SS

Ht see af

a LA a : mandible
moxilis—7 ~ t a.

exopodite

A :
endopodite liver

Bes j
ae
;
” 0
ovary ;
60 oe
100
5 chitin cooting 2004
enige: ms! of the
hypodermis
mondible
maxilla
mandible
liver ;
closing

muscles

|
J cells
fe chitin coating

chitin lining

[151]

Plate 13

Nos. 65-75. Adult, 10 transverse sections, stained with Ehrlich’s haematoxy-
lin and eosin. The sections progress from the anterior to the posterior end.

[ 152 ]

PLATE 13

antennule

anteana

[ 153 |

Plate 14

Nos. 76-84. Adult, 10” transverse sections. These sections follow those shown
in Plate 13.

| 154 |

ligament
\

forehead . ¢' [aa >
orehead 6p Aap hy oy \\ Sitannute
; x

excretory
giond B

*

Ij mandibular
palp

80 * 81

ganglion of
the antennule

84

Plate 15

Nos. 85-90. Adult, 10 transverse sections. These sections follow those shown
in Plate 14.

[ 156 J

100
mandibular
palp
200u
ventral chain of ganglia
Wir
Soe fn

rear soc of

excretory cland B —4-* & +.

end soc of

% £ ff *
excretory glond B— a ' Bee 7
4) tip cf Sete
mendible i . 1h
dorsal Wulsf * Ly i, :
mae endoskeletonS.s x
oy 4 .
ventral chain cf ganglia 44s ee maoxilie
8 ay & :
‘ x ~ £ % : ‘
moaxilfe —"* a ZL . mandible
% a >
ws Lae g-
\ :
87 Ma 88
ak first thoracic leg hy pastome
- €i
{© - yo axcretory giond B
p & excretory ’

gland A
A if : ot Stomoch

mandible ‘ 7 sw > mandible
a -

branchial plate-———"~

) of maxilla “ % 6 ai 1 j
\ \ €s
first thoracic leg 90

Plate 16

Nos. 91-96. Adult, 10 transverse sections. These sections follow those shown
in Plate 15.

| 158 |

PLATE 16

‘ eines . ‘ __—rear sac of
s *s : ae oe % ( = excretory gland 6

_ mandible
mandible ©

chain of 7,
gonglia + BE te

ae dees!
first Viva

thoracic leg 4

{e)

100

liver —
gland N-
200u

ventral chain ~

of ganglia
branchial plate —

93

“3rd leg

stomach _

‘dl : -_— liver
he ;
liver a % a 4 ‘ s
j liver — gland N
H \
\ =
} ‘ eho
‘“ ee Ws —+~ bronchial plate
aD A
‘ setae of j td a * f
branchial plate e mS
os ~ oe la “third thoracic leg
* “3rd thoracic leg a al ee
B i second thoracic leg
2nd thoracic leg 96 ~
3rd leg

[ 159 }

Plate 17

Nos. 97-102. Adult, 10, transverse sections. These sections follow those shown
in Plate 16.

| 160 ]

PLAIE (7

muscles supporting
the gut system

‘rear sac of food ball

rear sac of
excretory gland 8
liver

closing muscles
2

giond N

excretory gland G

=
Me

branchial plate
3rd leg

econd thoracic leg

—100
uterus excretory
gland ©
liver
; branchial
2004 plote

™ second
* thoracic leg

\
\

third thoracic leg

closing muscles

—bronchial plate

™ second thoracic leg

© —— third thoracic leg

[ 161 J

Plate 18

Nos. 108-111. Adult, 104 transverse sections. These sections follow those
shown in Plate 17.

[ 162 ]

PLATE 18

intestine

spiral
canal

2nd leg

genital lobe

[ 163 ]

—=clow of 2nd leg

intestine

105

giand
te)

genital
lobe

claw of 2nd leg

Plate 19

Nos. 112-120. Adult, 10, transverse sections. These sections follow those
in Plate 18.

| 164 |

PLATE 19°

< 9 = \ <3
i 14 furca

anus 3 ¥«)

ie) oe 2004
ii
rs in! ~ aoe ce
‘ chitin Vink Se we -

a coating

8 = 119

[ 165 ]

Plate 20

Nos. 121-127. Adult, 104 transverse sections. These sections follow those
shown in Plate 19, and conclude the sequence of transverse sections which began
in Plate 13.

Nos. 128-155. Adult, 10u frontal sections, stained with Ehrlich’s haematoxy-
lin and eosin. These sections progress from the dorsal to the ventral edge.

[ 166 ]

chitin
coating

chitin ry
coating

_ontennule

» medion
lens

lateral
lenses y

[ 167 |

Plate 21

Nos. 156-161. Adult, 10 frontal sections. These sections follow those shown
in Plate 20 beginning with No. 128.

[ 168 J

PLATE 21

rear soc of
excretory .
gland BY,

© ganglion of

Px

: .
& %

f ; . - antennule
A oe”
' te es
os 4 : antenna
,,

excretory

cerebrum _

A, -forehead

~
circular
muscles

€

seta of
~* + branchial

" ‘ plate
a 4

[ 169 ]

Plate 22
Nos. 142-145. Adult, 10, frontal sections. These sections follow those shown
in Plate 21.

1 170 |

PLATE 22

“antenna

. o \ — epidermal cells
c antennule 2
\ ; ; 2

antenno
~

antennule

ontenna

cerebrum
cerebrum

stomach
end soc of excretory giand BI

liver

o 143 ¥ ses

cerebrum _ °F
: * excretory

* v4 gland A
dorsal Wuist -

closing muscles -—.

net
}

setae of —— wT 2
branchial plote

ae . Pee
ae. Py . rear gut
eg a
% 4 \
i Ee *% : uterus
F : wt
OS A =< ny
a

144 ; i456 he

Civ]

Plate 23

Nos. 146-169. Adult, 10, frontal sections. These sections follow those shown in
Plate 22.

[ 172 ]

PLATE 23

_-antenna

ontennule

upper lip

base of antenna
cerebrum

closing
y closing muscles

seminal
receptacle

epidermal cells

esophagus |

endoskeleton

axcretory glond C

liver

seminal receptocie~

Plate 24

Nos. 150-154. Adult, 104 frontal sections. These sections follow those shown
in Plate 23.

1 174 ]

PLATE 24

taal

ontenna

upper lip
palp

esophagus
mandible
mandible

14 upper lip

polp
polp

mandible
Ist
leg
2nd

[175]

Plate 25

Nos. 155-161. Adult, 10 frontal sections. These sections follow those shown
in Plate 24, and conclude the sequence of frontal sections which began in Plate
20, No. 128.

| 176 |

PLATE 25

maxillo

maxilla branchial

opening ;

terminal
pincers of
3rd leg

ovary

rr hypostome

Plate 26

Nos. 162-175. Adult, 10 sagittal sections, stained with Ehrlich’s haematoxy-
lin and eosin. These sections progress from left to right.

[178 ]

PLATE 26

ies 164

chitin

lining
closing
muscles
liver branchial liver
plate ~¥J
branchial
- plate
egg
spiral -
canal spiral
conal
uterus

| 179 |

Plate 27

Nos. 174-178. Adult, 10 sagittal sections. These sections follow those shown
in Plate 26.

| 180 |

PEATE 27

branchial
plate
\

liver liver

liver

bronchial
plote

branchial
plote

3rd
leg

uterus

3rd ~~ “4 PF uterus

leg vacinal

spiral opening

canal
giend O

174 A 175 176

excretory gland A

mandible

mandibie —

maxilla

maxilla

3rd thoracic leg

axcretory
gland C

furca —

~reor gui
reor gut
furca

[181]

Plate 28

Nos. 179-182. Adult, 10m sagittal sections. These sections follow those shown
in Plate 27.

[ 182 ]

PEATE 28

mandible

excretory gland 8
“ excretory gland B
e

‘~ maxilla —
liver
SS -
& 4) seminal
Mi receptocle
2nd thoracic leg )
second leg~
qo rear gut
rear gut

Fa
mandibular paip $e - _antenna

mandible

~~

mondible

excretory gland B

maxilla — maxilla

a first leg—
Q LS 2 cel ae
Ist thoracic leg “ar pad EM

ventral chain stomach wal!

of ganglia

longitudinal

seminal gut muscles

receptacle
second leg-

ig 1
2nd thoracic coy % 4 ] (é
i‘: ” PY rear gut Be

genital Q

lobe »%
t

\*

-rear gut

18!

[183 ]

Plate 29

Adult, 10 sagittal sections. These sections follow those shown

[ 184 ]

PEATE 29

antenna

ot Oe antenna

antennule
7

mandibular palp
palp = cerebrum
mandible -
ventral tissue
nglia supportin
gangit _ cells of the / the ereen
stomach woll
hypostome
gland N
gland N —

2ndleg— 4

genital

spiral —
lobe canal
ovary —__.4 i -
i JS ovaty—
% ©
183 i ares
, . ee al
* was” 184 “ Crd
r, poe ontenna », antenna
antennule
oo _antennule
palp—__ _cerebrum
upper lip _
: _ cerebrum
upper lip —
base of ( _ base of
mandible antennule “~ antennule
ventral — d |
| gengii = goite
hypostomse ——4 _Sstomach :
excretory — stomach
gland ©
spiral canal
spiral —
canal ; ; : i
) \ J
‘ » , 2 ovary —-> : ee
>.> re a - £ ;
® . . é, Z
“os \ fo gt
4 Ox
~ se ned ~ ‘ — ovary

[ 185 ]

Plate 30
Nos. 187-191. Adult, 10 sagittal sections. These sections follow those shown
in Plate 29.

PLATE 30

giond L a

y. ganglion
W\, of the
, ae

' ‘

“stomach

antennule antennule
cerebrum

frontal lens

lateral lens = Intecol

lenses
Ist thoracic
leg

branchial plate

bronchial plate

| 187 ]

Plate 351

Nos. 192-195. Adult, 10m sagittal sections. These sections follow those shown
in Plate 30, and conclude the sequence of sagittal sections which began in Plate 25.

[188 ]

PLATE 3i

ontenna

forehead ; sy 5 antenns

upper lip
ontennule

mandible ganglion at

base of the

mandible
antennule

moxillo

closing muscles

-muscles supporting
~ the mandible

liver -

ovary

192 | 193

antennas

antennule

palp

—~ ganglia of

mandible the antenna

ganglia of +
the
mandible

closing muscles —

liver —¥

I 189 ]

Plate 32

Nos. 196-200. Adult, 20 sagittal sections, stained with Ehrlich’s haematoxy-
lin and eosin. The sections progress from the right side to the left.

[ 190 |

PEATE 32

end sac of
excretory
gland 8

196 . 197

198

i epidermal
“4 v4 cells
lateral << Zr,

lens *

duct from
liver into |

~
stomoch

stomoch
stomoch-

reor gut —

[ 191 |

Plate 33

Nos. 201-204. Adult, 20 sagittal sections. These sections follow those shown
in Plate 82.

| 192 |

PLATE 33

antennule_

eye —___-_

food ball —

rear gut —

ontennule
antenna

\ 1
\
frontal \
jens 4
\ of nee 57 1M
- mandibulor palp

~ spiral canal

~~, ‘ ; antenna

[ 193 ]

Plate 34

Nos. 205-208. Adult, 20 sagittal sections. These sections follow those shown
in Plate 33.

[ 194 ]

PLATE 34

pharynx
muscle = antenna iP antenne
a =
Me i
cerebrum se gland L
eS . cerebrum

maxilic
_ maxilla
ventral
chain of
ganglia ~Ist thoracic leg
gtond N ~ —— 2nd thoracic leg

claws of 2nd legs
=. vA

a RY

Zs

205

antenna ontenna

glond L
upper lip

teeth of

mandible teeth of

_- mondible
maxilla

chitin
" framework ~

of the head

C +—— Ist leg

hypostome

ventral chain _
of ganglia

giond N—
A*
‘ f —3rd leg
e995 - spiral 4
cane! » _ spiral
canal

Plate 35

Nos. 209-213. Adult, 20m sagittal sections. These sections follow those shown
m Plate 34, and conclude the sequence of sagittal sections which began in Plate 32.

| 196 ]

PEATE 39

_-antfenno

_- mandibular paip

teeth of
gland Bo = .. ¢ - mandible
: gland B_
maxilla
mandible
— branchial
liver plate
liver —
‘ aes epidermal
ovary cells
ovary -

209 ee ae

giond B

epidermal
cells

mandible

5 Atal
: AG gs
gp AS r o>
closing — 7 A : =} a &, #
; < "pial oh
muscles > ry oS
F . 4

liver

~<

een 212 |

[ 197 ]

Plate 36

Nos. 214-215. Adult, 10 frontal sections, stained with Ehrlich’s haematoxy-
lin and eosin. These sections progress from dorsal to ventral.

[ 198 ]

BLATE ‘36

2l14 liver

duct from liver
into stomach —

food ball

egg with nucleus aia [at a |_|

digestive fluid (from liver) surrounding food ball in stomach

entrance from ovary into uterus

nee gr

[ 199 |

Plate 37

Nos. 216-217. Adult, 10, frontal sections. These sections follow those shown
in Plate 36.

[ 200 ]

PLATE 37

(9) 100u

uterus | | | | { | Li |

epidermal
calls

216 ovary

5 ovor
liver y

closing
muscies

stomach —

217 egg nucleus

[ 201 ]

Plate 38

18-219. Adult, 10u frontal sections
7

Nos. 2 . These sections follow those shown
in Plate 37.

[ 202 ]

PLATE 38

218 liver

closing eS”

muscles

dorsal Wulst —____

219.

food ball

(a rear gut

oS

egg in uterus
seminal receptacle

liver

\
Ete aman caainaadl
a"
i wt

\ 3rd leg anus
fluid in seminal receptacle

Plate 39

Nos. 220-221. Adult, 10, frontal sections. These sections follow those shown
in Plate 38.

[ 204 ]

PLATE 39

seminal receptacie fe) 1004u

spiral cana! | |

— 899

iand : ®
g “copulation bladder

closing
muscles

giand N

ey \ 3rd leg opening of uterus

excretory gland G

Plate 40

No. 222. Adult, 10 frontal section. This concludes the sequence of frontal
sections which began in Plate 36.

No. 223. Adult, 10u transverse sections. The dorsal end of the section is at
left. The following sections progress from anterior to posterior.

[ 206 |

PLATE 40
excretory gland C ovary

closing muscles genital lobe

base of furco

222 excretory gland G opening of uterus

: antenna .
antennule upper lip

ligament

onten
225 antennule : nf mandibular palp

[ 207 |

Plate 41

Nos. 224-225. Adult, 10 transverse sections. These sections follow that shown
in No. 223.

[ 208 ]

PLATE 4!

0 eley7a
|
ep ele a eléad- L's

224 igament antennule

excretory gland B

frontal! lens of eye

*

mondibular palp

225 excretory gland B

antenna

| 209 J

Plate 42

Nos. 226-227. Adult, 10” transverse sections. These sections follow those
shown in Plate 41.

[ 210 ]

PLATE 42

lateral lans of eye mandibular palp

optic nerve

| /

/ ee

cerebrum upper lip
f

lateral lens of eye

pigment

227 excretory gland mandibular palp

[ 211]

Plate 45

Now. 228-229. Adult, 104 transverse sections. These sections follow those
shown in Plate 42.

[ 212 ]

PLATE 43

) 100u

cerebrum Chit ti

upper lip

mondibular palp

228

cells of gland M
cerebrum

mandible

mandible

excretory giand B

\
\
| ; \
| \
\
229 excretory gland B mandibular palp

Plate 44

Nos. 230-231. Adult, 10, transverse sections. These sections follow those
shown in Plate 45.

[ 214 ]

PLATE 44

excretory gland A mandibular polp

| ns maxilla

wo

“ "2 mandibular palp
=

230 excretory gland B exopodite plate of mandible

us

excretory gland A :
“rake-shaped organ’

atrium

stomach wall

23 | excretory gland A

exopodite plate of mandible

Plate 45

Nos. 252-233. Adult, 10 transverse sections. These sections follow those
shown in Plate 44.

| 216 |

PLATE 45.

endoskeleton

\ :
2352 setae of exopodite of mandible

ventral chain of ganglia

duct from fiver into stomach
3 endoskelefon maxilla

»

maxilla

233

mandible

Plate 46

Nos. 254-255. Adult, 10m” transverse sections. These sections follow those
shown in Plate 45, and conclude the sequence of transverse sections which began
in Plate 40, No. 223.

[ 218 ]

PLATE 46

dorsal Wulst endoskeleton
liver mandible ventral chain of ganglia

maxilla

hypostome
maxilla
-

mondible

a 4

Oe |

234 rear sac of excretory gland 8
duct from liver into stomach
maxilla
liver hypostome

/

tissue supporting
the stomach

23D sPomach liver oxi

[ 219 ]

Plate 47

Nos. 236-237. Adult, 10 sagittal sections through the genital region. The
sections progress from left to right.

PLATE 47 as a
reor gut nucieus Etec ates)

chitin lining

apiral conal 236 chitin coating of the hypodermis

tood ball rear gut

excretory
gland G

branchial
plate

2aT spirel canal eqg

Plate 48

Nos. 238-259. Adult, 10m sagittal sections. These sections follow those shown
in Plate 47.

Co
iw)
to
bo
a

PLATE 48

seminal receptacie

rear gut

stomach gland O

egg

238 spiral canal

giond © rear gut

stomach

seminal
receptacie

239 spiral conal

225 |

Plate 49

Nos. 240-241. Adult, 10, sagittal sections. These sections follow those shown
in Plate 48.

[ 224 |

PLATE 49

re)
giond Oo : eee Peet

anus

seminal receptacle . "copulation bladder” 240

genital lobe —

241 chitin "stick"

Plate 50

Nos. 242-245. Adult, 10m sagittal sections. These sections follow those shown
in Plate 49.

PEATE 50

242 2nd thoracic leg furce

69g

seminol
receptocile
<<

Ny

: ‘
243 2nd thoracic leg furca

uterine opening

Plate 51

Nos. 244-245. Adult, 10u sagittal sections. These sections follow those shown
in Plate 50.

PEATE 5]

\
baat ‘
2nd leg 244 vaginal opening

nucleus

' ; ” chitin “stick”
“copulation bladder genital lobe 245

[ 229 ]

Plate 52

Nos. 246-247. Adult, 10 sagittal sections. These sections follow those shown
in Plate 51.

[ 230 ]

ry

PEATE 32

giand O

>— chitin
coating
™? —~ epidermal!

cells

246 spiral conal

gland 0

| 231 |

Plate 53

No. 248. Adult, 10m sagittal section. This section follows those shown in
Plate 52, and concludes the sequence of sagittal sections which began in Plate 47.
No. 249. Adult, 20 sagittal section through the soft parts of the valve.

[ 232 ]

PEATE 53

fe) 50u

ovory

x

248 spirol canal

ovary

gland B—

excretory gland 6

249

end sac of excretory gland B

[ 233 J

Plate 54

No. 250. Adult, needle dissection. The antennules as seen from below. The
eye 1s also seen in position.

No. 251. Inner face of the left antennule.

No. 252. Terminal podomeres of the right antennule. The bases of some of
the natatory setae are shown.

No. 253. A distal portion of the right antennule.

No. 254. The second and third podomeres of the antennule.

| 234 J

PLATE 54

POP

254

[ 235 ]

Plate 55

No. 255. Adult, needle dissection. Inner face of the left antennule showing
the attachment to the forehead.

No. 256. Portion of the proximal podomere of the left antennule.

No. 257. Distal end of the left antennule.

No. 258. Basal podomere of the right antenna. Anterior is at the top, ventral
at the left of the photograph.

No. 259. Inner face of the left antenna.

No. 260. First podomere of the endopodite of the left antenna, showing the
“sense organ’ and the natatory setae.

No. 261. Distal end of the left antenna, showing the attachment of the termi-
nal claws.

[ 236 |

PLATE. 55

—— basal podomere

ie chitin rod
Pe, me tS ot i

260 »26l

[ 237 J

Plate 56
No. 262. Inner faces of the left antenna and mandible, showing their respec-
tive positions.
No. 263. Terminal claws of the antenna.
No. 264. Endopodite plate of the mandible.

No. 265. Antennae.
No. 266. Branchial plate of the right mavnilla.

[ 238 |

PLATE 56

BYP, | 0 100K

fen 50

265 266

239 |

No.
No.
No.
No.

267.
268.
269.
270.

Plate 57
Inner face of the left antenna.

Anterior portion of the body in needle dissection.
Distal teeth of the mandible.

Anterior portion of the body as seen from below

[ 240 ]

PLATE 57
ee ie (OPH

process
above ist leg

Endbige!

antenne
x

267

mandibular

palp
i
mandible

te) 1004

J
0 100
boa el

antennule
x

right antenna i

left antenna

\
- \
/ 2 . @ \
mondible “& = ey
maxilla —~ \ E
x <
dof palp
Ist leg—— F
i oe exopodite
hypostome ‘
— \
left Ist leg mandible
maxilla

~ brachial plate —

270

[ 241 ]

Plate 58

No. 271. Inner face of the left mandible.

[ 242 ]

OS

7001

PLATE 98

(as1podopua) djod

ayoyd ayipodaxe

ty
mlecsoxe yO edja

$ipos ajosnw

[ 248 |

Plate 59

No. 272. Second thoracic legs and genital lobes.

No. 273. Terminal claw of second thoracic leg.

No. 274. Mandible, manilla, and first thoracic leg in position.

No. 275. First thoracic leg. Anterior is at the top, and ventral at the nght of
the photograph.

[ 244 ]

PLATE 59

+

exopodite

[ 245 ]

Plate 60

No. 276. Outer face of right mandible, manilla, and first thoracic leg.
No. 277. Third thoracic leg.

No. 278. Ovary.

No. 279. Genital lobes as seen from below.

No. 280. Mandibular teeth.

| 246 |

PLATE 60

279 280

| 247 |

Plate 61

Nes. 281-282. Adult, 10u frontal sections through the eye. The sections pro-
gress from dorsal to ventral.

PLATE 61

fe) Ke) 204
PEACE ES ty

anterior
extension
of the eye

lotera!
lenses

/
28) pigment optic cup

lobes of the
4 frontal median lens

[ 249 ]

Plate 62

No. 283. 10 frontal section through the eye, following the sections shown in
Plate 61.
No. 284. 10, frontal section through the bases of the antennules.

[ 250 ]

PLATE 62
frontal median lens lil |

05: ¢

283 pigment

\ eobeneed
284 \

ganglion of the antennule

[ 251 ]

Plate 63

Nos. 285-286. Adult, 10, frontal sections through the middle of the body. The
sections progress from dorsal to ventral.

PLATE 63

dorsal Wulst

Y gland N
100u
excretory
gland ©
0
excretory
gland ©

286 gland N

[ 253 ]

Plate 64

Nos. 287-288. Adult, 10 frontal sections through the middle of the body.
These sections follow those shown in Plate 63.

PLATE 64

gland N

excretory
gland G
excretory
gland C
aie
endo- 2
skeleton :
50u
4
0

288

—
bo
Or
or
a

Plate 65

No. 289. Adult, 10, frontal sections through the middle of the body. These
sections follow those shown in Plate 64.

No. 290. Adult, 10 frontal section through the cerebrum, excretory gland A,
and dorsal wulst.

| 256 |

PLATE 65

endo-
Skeleton

duct of
excretory
gicnd ©

excretory
gland A

290

dorsal Wulst

Plate 66

No. 291. Inner face of the nght valve.

PLATE 66

291

[ 259 |

Plate 67
No. 292. Right valve seen with transmitted hght.
Nos 293-296. Left valve seen with double polarized light in successive posi-
tions.
No. 297. Adult, 10, frontal section through the cerebrum.

[ 260 ]

PEATE 67

20
Yabo

294

299

cerebrum

yon ®

(eo. %,e
296 297 excretory gland A

[ 261 ]

Plate 68

Nos. 298-501. Adult, 104 frontal sections through the central nervous system.
The sections progress from dorsal to ventral.

| 262 ]

PLATE 68

excretory gland A

a.

BS

dorsal
Wulsi

cerebrum

cerebrum-

ee
\ Sate

300 dorsal Wulsr 30I 0 50u

[ 263 |

Plate 69

Nos. 302-305. Adult, 104 frontal sections through the central nervous system.
These sections follow those shown in Plate 68.

| 264 |

PLATE 69

ganglion of the antenna

endo-
“ skeleton
esophagus
¢
302 303
: . al
-
endo-
skeleton

endo-
skeleton

304 circumesophageal ganglion 305 6

50u

[ 265 ]

Plate 70

Nos. 306-309. Adult, 10u frontal sections through the central nervous system.
These sections follow those shown in Plate 69.

| 266 |]

PLATE 70

mandible

307 ventral chain of gangiia

gangiicn of _*

the mandible

_hypostome

308 Ganglion of the maxilla 309 gangltog opine

first thoracic leg

Plate 71

Nos. 310-312. Adult, 10 sagittal sections through the left first thoracic leg.
These sections progress from the left to the right side.

| 268 |

PEATE (71

exopodite plate

'

\

a <a oe
Wy

muscles of the mandible——

masticatory process of maxilic.

muscies of the mandible
/ \ prolopeciis 310 endopodite palp

masticatory process of first ‘horacic leg

3rd leg

endopodite palip

Sil Masticatory process 3rd teg

ween

muscles of the mandible —

ganglion of the maxilia oe

Calabi na 312 \ stsonaditeyeey

masticatory process

[ 269 ]

Plate 72

Nos. 513-518. Eighth instar, 10” transverse sections, stained with Ehrlich’s
haematoxylin and eosin. The sections progress from anterior to posterior.

PEATE 72

antennule

antennule antennule

antenna antennule

antenna
XX

ee o

antenna

315 antenna 314

antennule
sf

antenn \
antennule antennule x \ antennule
wf \ \ /
Spgs a we!
a
{ a a 4
2 ar
oot a
is
i:
‘ ”
315 Reece SIG % dover ite
CUNT) antenna
antennule
: \ ontennule
antennule antennule ON ene
\
. X
ORI
ee
ts re
aK
, Ve «<
i hoe
ah we
S&,. >:
\ -

417 upper lip 318 upper lip

(6) 100pn

[ 271 ]

Plate 73

Nos. 519-322. Eighth instar, 10” transverse sections. These sections follow
those shown in Plate 72.

| 272 |

PEATE 73

antennute

antennule

excretory gland B —___

chitin coating of hypodermis

mandiputar paip

\
antennute | \
\ antennule | \
} 319 \ mandibular pulp

cerebrum

entenna

_-- excretory gland B

—antenne
--mandibular palo

excretory giand B

forehead
hinge

te
320 mandible ceredrum \ ;

cerebrum

mandibular palp

hinge

. & ee
ape . \
eye | 32} ‘ mandibular palp

upper lip

——--—-—-- chitin coating of the vaive

———-—- antenna

mandibular palp

322 | mandible

\
maxillary polp

spiderma! cells

273 |

Plate 74

Nos. 323-326. Eighth instar, 10” transverse sections. These sections follow
those shown in Plate 73.

[ 274 ]

mondibie —_
exopodite plote of mandible —__

masticatory processes of maxiiio ——

excre i
ade aiend dorsal Wuist

t f
323 eeaible ae paip

—— excretory giansd
——base of antenna

— mandible

A

324 masticatory processes
of the moxillia

dorsal Wulst

mandible —

masticatory processes of maxilia

dorsal Wulst

325 \ i; % mondible

masticatory processes of maxilla

ventral chain of gangita

hypostome

mondibie

maxiltia

hypostome

—
bo
~J
or
—

Plate 75

Nos. 327-330. Eighth instar, 10u transverse sections. These sections follow
those shown in Plate 74.

[ 276 ]

PLATE 795

maxilla —_

Ist thoracic leg —

bronchial plate
\ stomach

\ |
- maxilis

hypostome

chitin connective of closing muscles

giand N

I \

\

328 ist leg \ ier lag

hypostome

closing muscles ——

ist thoracic leg-

closing muscles
|

329 ist thoracic ieg

closing muscles

~chitin coating of the epidermis

[ 277 ]

Plate 76

Nos. 331-354. Eighth instar, 10m transverse sections. These sections follow
those shown in Plate 75.

[ 278 ]

PLATE 76

branchiol plate

base of 2nd jeg

closing muscles
branchial piate

base of 2nd leg

branchial plate

332 andieg

2nd thoracic leg

2nd thoracic leg

posterior end of Ist leg (endopodite)

3rd leg

bronchial plate

2nd thoracic leg

{e) 100u

ho
=I
vo)
a

Plate 77
Nos. 335-338. Eighth instar, 10” transverse sections. These sections follow
those shown in Plate 76.

[ 280 ]

PLAIE 77

3rd leg
’ Aniagen of genital organs

i

branchial plate -

=
3rd leg 2nd thoracic leg——-——————
end jeg
‘\ food ball in rear gut
\ 2nd leg |
\ \ ;
\, \ \ |

335 \ 3rd thoracic jeg

2nd thoracic leg

branchial plate

pranchiai

: 1 rear gul
— /

336 / / 3rd leg

3rd thoracic leg-

2nd thoracic feg

Anlagen of
} genital organs

} \

\ 3rd thoracic ieg
|

2nd thoracic leg

—- Anlage of ovary

plate

genital organs

i i .

| 337 | \ Aniagen of
ee \
|

Plate 78

Nos. 389-349. Eighth instar, 104 transverse sections. These sections follow
those shown in Plate 77. This ends the sequence of transverse sections starting on
Plate 72.

| 282 ]

PLATE 78

rw > ft

Foal
: *

Sag 340

343 344
7?
SO g
346

ud 348 349
347

Plate 79

Nos. 350-355. Eighth instar, 104 transverse sections, stained with Ehrlich’s
haematoxylin and eosin. Sections progress from anterior to posterior.

[ 284 ]

dorsal Wulst

FEATE 79

r
liver.

closing muscles—_._..__&

stomach 350

\
\

mandible mandibular
teeth palp
_— junction of palp and mandible
__ exopodite plate of mandible

stomach
;

mandible /
maxilla
mandible

closing muscles

liver

exopodite

mandible ir
maxilla plote

maxilia

“ a "roke-shaped organ”
352

a

———-— mandible

++ exopodite plate of mandible

| maxilla

353 maxilla

“rake-shaped organ"

Plate SO

Nos. 554-557. Eighth instar, 10m transverse sections. These sections follow
those shown in Plate 79.

[ 286 |

PLATE 80 ey Ue

liver
i

maexilic

liver

maxilla
ventral chain of ganglia

hypostome

closing muscies

stomach liver

}
j

Ist leg j hypostome |

i |
moxilte maxilla

399

brenchial plate ——- ——— %&%

food bali

maxilia

ist leg 356

branchial plate

i \ x
ial plate 1st le Ist leg io) 100z
branchial pia st leg \ 357 i eal

ee hypostome

Plate Sl

Nos. 358-561. Eighth imstar, 10u transverse sections. These sections follow
those shown in Plate 80.

PLATE 81 bose of 3rd leg feod ball

branchial plate with setoe —

sad Ist leg
end ieg branchiai plate
2nd leg

bronchial plate

“——-— 3rd leg

359 branchial plate

f \
3rd leg / 2nd leg \ Ist leg
2nd leg

sf

| | ee \
‘: | i

2nd leq

hinge line Hy et x

2nd leg

28
~ branchial plate with setae

; é ssi? BP nec
\ x! se
<<. \I Antagen of organs in genital lobe
; 4 e aN

Li

36l | 2nd leg

OOu

Plate S82

Nos. 362-365. Eighth instar, 10” transverse sections. These sections follow
those shown in Plate S1. This concludes the sequence of transverse sections begin-
ning on Plate 79.

[ 290 ]

PLATE 82

Anlagen of spiral canal

362

epidermal cells — ———

$rd leg ——__..

hinge 3rd ieg

3rd leg

lO0u

[ 291 ]

Plate 83

Nos. 366-568. Eighth instar, 10m transverse sections. Sections progress from
anterior to posterior.

PLATE 83

mandibular palp

mandibular palp

mandibular palp

368

\
gland L upper lip

[ 293 ]

Plate S4

Nos. 369-371. Eighth instar, 10a transverse sections. These sections follow
those shown in Plate 83.

| 294 ]

PLATE &4

fri.) i) «(369

ontennule ——

antenna

mandibular paip

end claws of
mandibuior paip

entennule

antenna

/ > se ~

370 teeth of mandible A .

i Ag eer

ae

a
: om

e &
. |

© 3
yr

cerebrum

moandibte

mandibular paip—_

f \ EN
maxilla maxilla mandibular polp

[ 295 |

Plate 8d

Nos. 372-873. Eighth instar, 10m transverse sections. These sections follow
those shown in Plate S84.

[ 296 ]

PLATE. 85

S12

{e}
E cerebrum

504u

mandibulor palp

“roke-shaped organ”

"

"rake-shaped organ"

excretory giand B

excretory glond B

exopodite plate of mandible

} maxilla
375 hypostome

[ 297 ]

Plate 86

Nos. 374-376. Eighth instar, 10m transverse sections. These sections follow
those shown in Plate 85.

[ 298 |

ELATE 86 excretory gland A

excretory giond B

mandible —

x

oe
exopodite plate of mendible —————

excretory gicnd A
excretory gland 8 \ \

mandibular palp

exopodite plate

dorsal Wulst

mondible

exopodite plate of mandible

375 ventral chain of ganglia

endoskeieton ——

50u branchial plate

maxilla hypostome maxilla
Ist leg Ist leg a7¢6

Plate 87

Nos. 3877-879. Eighth instar, 10 transverse sections. These sections follow
those shown in Plate S6.

| 300 |

PLATE 87

branchial plate ——————

dorsal Wulst
x

ne

branchial
plate

Ist leg

closing muscles ——

branchial plate -——

379

+

a

Ist leg

[ 301 |

|

hypostome

378

stomach
y,

Ist leg

liver

. me ee
. Dy ad branchial plate

liver

branchial plote

Plate S88

Nos. 380-381. Eighth instar, 10 transverse sections. These sections follow
those shown in Plate S7.

[ 302 ]

PLATE 88

hinge
stomach liver

closing

eae

closing :
muscles

= bronchial
plate
branchial ;
plate :
gland N

€ ’ 1s : » m : 3
gland N \
Tst leg Ist leg 380

) 50u
i

___-———_ slasing
muscles

closing
muscles

branchial plate / 2nd le ond leq branchial plate

lst leg Ist leg
381

[ 303 ]

Plate 89

Nos. 582-385. Seventh instar, 10” transverse sections, stained with Ehrlich’s
haematoxylin and eosin. The sections progress from anterior to posterior.

[ 304 ]

0 lO0n

ntenna

}
ontennule

384 antenna

antennule

subdermal celis

385 antenna antennule antenna

[ 305 ]

Plate 90

Nos. 386-389. Seventh instar, 10 transverse sections, stained with Ehrlich’s
haematoxylin and eosin. These sections follow those shown in Plate 89.

[ 306 |

PLATE. 90

wg -
ey : ; 3
Ga me *
Be { = “2 % ee of ontennule
a %

7
° ~
&

3 . g; 7) x ie i Le ot
yt a }
U he :

ay > excretory glond 8
. \
% iy

j

i
386 antenna antennule

antenna

fe
clows of antenna

~ > Hl |
AN Hig
Th, Af
; claws of antenna
eee lip

388 anrenna

claws of antenna

389

base of antenna

upper lip

[ 307 |

Plate 91

Nos. 890-3893. Seventh instar, 10u transverse sections, stained with Ehrlich’s
haematoxylin and eosin. These sections follow those shown in Plate 90.

[ 308 |

PEATE Sl

stomoch
}

330 mondibulor palo

mondioduiar palp

~~ mandibutor paip

~

\
392 poly mondible Upper! EP

chitin lining of the epidermis ————

Se)

/ upper lip \
base of mandibular paip \

mondibular palp

[ 309 J

Plate 92

Nos. 394-397. Seventh instar, 10p transverse sections, stained with Ehrlich’s
haematoxylin and eosin. These sections follow those shown in Plate 91.

[ 310 ]

396

RELATE 92

liver

mondibie

/
exopodite plate of mandibie

maxilla

maxilla ——_

stomach

|

upper lip

‘ aoe
ake te 3
re. FE + mandibular palp

endoskeleton

4 _- mandible
6
¥

SOT.

| 311 J

"rake- shaped orgons"

395 upper lip

°
i

|

|

}
exopodite plate
of mandible

~exopodite plate of mandible

closing muscles

masticatory processes
of maxilla

Plate 93

Nos. 398-401. Seventh instar, 10u transverse sections, stained with Ehrlich’s
haematoxylin and eosin. These sections follow those shown in Plate 92.

[ 312 ]

PLATE 93

stomach 9 1004

ventro} chain of ganglia

masticatory processes of maxilia

liver

398 maxilla

hypostome

Sed leg

$39

~
x :
3rd ieg
rear gut
hypostome merilia
Ist leg branchial
ist leg plate
a a X branchici plate of maxilla
4 ft. Ae
Maney Gy
ite es rear gut Anlagen of
y /¢ ae genital organs
festa. \ , é
7 bey s
400 ist leg Ist leg ie
hypostome
base of 2nd {eg LL. a a
%
“Neti,
3rd leg te
{
. ;
i
¢
base of 3rd leg

: we

oe AN,
Nae

4O| 274 tego base of 2nd leg | 3rd 'eg branchial

Ist leg piote

[ 313 J

Plate 94

Nos. 402-405. Seventh instar, 10u transverse sections, stained with Ehrlich’s
haematoxylin and eosin. These sections follow those shown in Plate 93. This con-
cludes the sequence of transverse sections which began on Plate 89.

[ 314 |

PLATE 94

(e) 1004

_ Aniogen of spiral canal

— genital lobe

= setae of branchial plate

402 3 ae leg | Nara “4 ai

2nd leg 2nd Py \ « %, ”

Ist leg

403 de 3 : %.
Ne ® =
\ fey {yg

d f
37se x
j} ee
/ \ \ »
Bae \
‘A : 3rd leg | \ \ Bra. leg
oi 2nd leg \ x
a yx 2nd leg \,
ay Ist leg
at Zi ve :
A jj

« chitin coating of the shell
») rs x
PQ a

404 | | Sra teg ae

~
405 2nd leg \ 3rd leg

[ 315 ]

Plate 95

Nos. 406-413. Seventh instar, 10m transverse sections, stained with Ehrlich’s
haematoxylin and eosin. The sections progress from anterior to posterior.

[ 316 |

PLATE 95

am x 406

) antennule
ow .

na ta
Peg 7
‘ *
he Ls omen
x

408

: : é antennule 4|
ae
t, “aio

antennul

: Ses pharynx muscle

~ontenna

upper lip ene

fms, antennule
a ‘

mandibular
palp

upper lip

gt Bere

Ss
antenna-_

antennule

. foe
% ee
. eRe Ln
A *
3 eee
eA
¥

407

ntennule

:
A Re ga J

a

eye
409 Ra

lee

eae -
Beas ia a

y,

412 413 gland L

[317]

claws of

oe
Yop

antenna

gland L

Plate 96

Nos. 414-419. Seventh instar, 10m transverse sections, stained with Ehrlich’s
haematoxylin and eosin. These sections follow those shown in Plate 95, and con-
clude the sequence of transverse sections.

[ 318 J

PLATE 96
4i4 ye : antenna 415 eye

o.
?

¢

mondibuylar palp mandibulor polp mandibular /
palp upper lip
dorsal Wulst

and sac of excretory gland B stomach /

* % i
®*
heal a he

417 / Sy

mandible “rake-shaped organ"

maxillary mandibte

palp maxillary palp

mandible

yer dorsal Wulst

masticatory processes masticatory process Z é hypostome
of the maxilla of the maxilla masticatory processes

\
of the maxilla 419 moxa
418 — “roxe-snaped organ"

[ 319 ]

Index

Accessory cell, 64
Adductor muscles, see closing muscles
of mandibles, 26
Adjustor muscles of mandible, 25, 27
Adult, 3, 4-78, 84, 90, 94-95, 100, 102,
103-109, 114, 128-268
Algae, 57, 81, 84, 89, 91-92, 99
Alpha-quartz, 69
Anlage, of first thoracic leg, 98
of furca, 97
of maxilla, 97
of second thoracic leg, 98
of sex organs, 99
of third thoracic leg, 99
Antenna, 4, 8, 16, 17, 19-24, 27, 41, 50,
60, 82, 83, 84, 94-100, 111-113,
236, 238, 240
Antennule, 4, 8, 15, 16-19, 20, 21, 27,
40, 49, 50, 60, 82, 83, 94-100,
111-113, 234, 236, 250
Anus, 15, 57, 59
Appendages, 4, 16-45, 61, 82, 94-95,
110-114; see also antenna, an-
tennule, first thoracic leg, man-
dible, maxilla, second thoracic
leg, and third thoracic leg
Atrium, of mouth, 15, 24, 28, 29, 31,
38, 54, 57, 58
of vagina, 15
Axial filament of scolopoide, 64

Balance, 8, 16, 19
Bioluminescence, 53
“Bluntness,” 104
Body, 4, 49, 64, 240
segmentation, 4, 52
wall, 34, 48, 64, 74, 82
Branchial plate, of first thoracic leg, 14
of mandible, 8
of maxilla, 12
82, 238

Brooks’ law, 101-102

9 9 9F 9R 9 9
, ol, 34, 35, 36, 39, 43,

Calcite, 69
Caleium carbonate, 61, 67, 71-72

Cerebrum, 19, 23, 59, 98, 260
Chitin, 27, 49, 61, 69-71, 83
coating of the caleareous layer, 61,

65

coating of the epidermis, 63, 64, 65,
he

lining of the epidermis, 34, 63, 64,
74, 82

“stick,” 45, 77
Circumesophageal ganglion, 59-60
Claws, of antenna, 3, 8, 20, 21, 22, 24,
96, 236, 238
of mandible, 12, 26
of maxilla, 12, 35
of second thoracic leg, 14, 39, 40, 41,
84, 100, 244
of third thoracic leg, 14, 44
Cleaning, 14, 41, 48
Climbing, 8, 14, 16, 19, 20
Closing muscles, 34, 50, 53, 56,
Commensalism, 92
Copulation, 38, 45, 46, 57, 78
bladder, 74, 76
gland, see gland O
Cypridopsis, 1

9

vidua, 2-3

7
(

9
oO

Deutocerebrum, 19, 59-60
Diatoms, 69, 91-92
Diductor muscles of mandible, 27
Digestive fluid, 15, 54, 59

system, 15, 57-59; see also stomach,

liver, rear gut, and intestine

Diverticula of gland B, 51
Dorsal wulst, 15, 58
Duplheature, 61, 64, 65, 66, 67, 71

Egg, 46, 57, 74, 75, 77, 79, 80, 81, 87,
90)
laying, 45, SO-S1
shell, 57, 76, 79-SO, 95
“Elongation,” 108
Endbiigel, 32
Endopodite, of antenna, 8, 21, 22
of antennule, 4, 17

[ 321 ]

of first thoracic leg, 14, 38-39, 9S

of mandible, 8, 24, ie

of maxilla, 33-34, 3

of second thoracic es, 39

of third thoracie leg, 48
Endoskeleton, 19, 28, 26, 35, 38, 40,

49-50, 53, 56, 58, 60, 100

End sae, 51
Epidermal cells, 51, 62, 63, 71
Epidermis, 15, 50, 60, 61, 62, 66, 73
Esophagus, 15, 49, 50, 54, 57, 58, 60
Exeretory gland, A, 15, 50, 53

B, 15, 50-52, 61, 96

C, 15, 50, 52-53, 56
Exopodite, of antennae, 8, 21, 22

of antennule, 18

of first thoracic leg, 3, 14, 36, 38

9

of mandible, 8, 24, 26,

of maxilla, 12, 34, 74, 2

of third thoracic leg, 43
Extensor muscles, of antenna, 23

of antennule, 16, 19

of mandible, 27

of manilla, 35

of second thoracic leg, 41, 84

of third thoracic leg, 44-45
Eye, 4, 48-49, 248, 250

Family Cypridae, 1
Fecal pellets, 15, 59
Feeding, 4, 12, 24, 31, 36, 59, 61, 83
First thoracic leg, 12, 14, 15, 39, 33, 34,
36-39, 41. 50, 56, 57, 94-95, 98-
100, 112-118, 244, 246, 268
“Flagellum,” 47, 9S
Flange, 65, 66, 67
groove, 60
strip, 65
Flexor muscles, of antenna, 23, S4
of antennule, 16, 19
of mandible, 27
of maxilla, 35
of second thoracic leg, 41
of third thoracic leg, 44-45
Food, 15, 26, 54, 91-92
balls, 15, 54, 5
Forehead, 4, 8, 16, 20, 27, 48, 5:
Frontal optic cup, 48, 60
sections, 128-140, 166-176,
252-256, 260-266

4)

198-206,

Furca, 4, 15, 45, 47-48, 60, 94-95, 97-
100, 112-113

Ganglion, circumesophageal, 59-60
of antenna, 23, 24, 59
of afitennule, 19, 59
of first thoracic leg, 38, 59
of mandible, 27, 59
of maxilla, 36, 59
Genital lobes, 15, 45-47, 76,
244, 246
Genus Cypridopsis, 1
Germinal zone of ovary, 75
Girdle of hypostome, 12, 31, 36
Gland, L, 15, 54-55, 58, 100
“M,” 27,.59-56
maxillary, see excretory gland C
N,, 15, 38, 53, 55, 56, Si, 400
Oe. 15, 50; 560-57 16
of the antennule, see excretory gland
A
of the first thoracic leg, see gland N
of the upper lip, see gland L
“shell,” see excretory gland B
Growth, and heat, 87
and light, SS-S89

~

td lard
zone of ovary, 75

77, 100,

Hatching of eggs, SO

Head, 4, 12, 49

Heat, and growth, 87
tolerance, S85-S6

Height-length ratio, 115-116

Hepatopancreas, see liver

Hinge, 3, 60

Huxley’s formula, 105-106

Hypodermis, 51, 52, 54, 61,

Hypostome, 4, 22, 15, 29- 31, 33, 36. 39)

49, 50, 57, 60, 63

“Tnner lamella,” see chitin lining of the
epidermis
Inner margin, 66
Instar, 1, 84, 90, 94-96, 103-106, 111
2, 90, 94, 95, 96-97, 103-106, 111
3, 90, 94-95, 97, 103-106, 111-112
4, 90, 94-95, 97-98, 103-106, 111-113
5, 90, 94-95, 98, 103-106, 112-113
6, 90, 94-95, 98-99, 103-106, 113
7, 90, 94-95, 99-100, 103-106,
304-318
8, 90, 94-95, 100,
302

113,

103-106, 113, 270-

9, see adult
Intestine, 15, 57, 59

Lacunae, 63
Lateral optic cups, 48, 60
Lenses of eye, 48
Life span, 90
Ligament, 61, 82
Light and growth, 88-89
Line of concrescence, 65, 66
List, 65
strip, 66
Liver, 15, 50, 52, 54, 60, 61, 75, 96-99
Loop of hypostome, see ce of hypo-
stome
Lumen, of excretory gland B, 51
of excretory gland C, 53
of gland O, 57
of liver, 54
of uterus, 75

Mandible, 4, 8, 12, 15, 24-27, 29, 31, 41,
49, 50, 55, 57, 60, 94-100, 111-
113, ae 249, 244, 246

“oland,” see “gland M”

“Miastica tory” processes, 3, 12, 31, 33,
B40, 00,07

Maxilla, 4, 12, 15, 30, 31-36, 39, 41, 50,
57, 60, 94-95, 97-100, 111-113,
244, 246

Maxillary gland, see excretory gland C

Median eye, see eye

“Micro-teeth,” 66

Middle cell of scolopoide, 64

Molt stages, see instar

Molting process, 81-83

Motor nerves, 24, 31, 59, 60

Mouth, 15, 24, 28, 31, 54, 58, 96, 98,
160
Muscles,
adductors, of mandibles, 26

see closing muscles

rc OF

of valves,
adjustors of mandible, 25, 27
closing, 34, 50, 53, 56, 73
diductors of mene he
endoskeleton, 49-50, 53
excretory gland, A, 50

Be oz

C, 53
extensors, of antenna, 23

of antennule, 16, 19

of mandible, 27

of maxilla, 35
of second thoracic leg, 41
of third thoracic leg, 44-45
first thoracic leg, 38
flexors, of antenna, 23, 84
of antennule, 16, 19
of mandible, 27
of maxilla, 35
of second thoracic leg, 41
of third thoracie leg, 44-45
furca, 48
hypostome, 31
occlusor, see closing muscles
pharynx, 58
sears, 73-74
uterus, 46
vagina, 45

Natatory setae, 3, 8, 16, 17, 18, 19, 20,
21, 22, 26, 83, 97, 98, 234, 236

Nauplius, see instar 1

Nervous system, 59-60; see also cere-
brum, cireumesophageal gan-
ghon, deutocerebrum, protocere-
brum, tritocerebrum, and ven-
tral chain of ganglia

Normal pore canal, 64

Nurse cells, 75

Oocytes, 75
Oodgenesis, 75

Optic cups, 48

Optic nerves, 49, 60
Order Ostracoda, 1
Organe chemocepteur, 18
Ostrapodes,

Outer lamella, 61, 65
Ovary, 61, 74, 75, 94-95,
Overlap, 3, 65, 67

100, 246

Palp, of first thoracic leg, 14, 39
of ‘mandible, 8, 12, 24, 26, 27, 57, 97
of maxilla, 12, 33, 35, 36, 98

Paragnaths, 31

Parasites of ostracods, 92-95

Parthenogenesis, 75, 77, 78

Peribuceal ring, 60

pH tolerance, see tolerance

Pharynx muscle, 5S

Phototaxis, S7-SS

Pigment, of eye, 48

[ 323 ]

of epidermal cells, 63
Pincers of third thoracie leg, 15, 43. 44,
45
Pionocypris, 2
Protocerebrum, 49, 59-60
Protopodite, of antenna,
of antennule, 17
of first thoracic leg, 14, 36, 38, 39, 98
of mandible, 8, 24
of maxilla, 32
of second thoracic leg, 39, 41
of third thoracic leg, 41, 43, 45

val

Radial pore canal, 64

Rake-shaped organs, 12, 29, 31
100

Rear gut, 15, 57, 59

Rear sac of excretory gland B, 51, 53

Reproduction, see parthenogenesis and
syngamic reproduction

rate, 89-91

Reproductive system, 74-78; see
copulation bladder, ovary,
inal receptacle, spiral
uterine openings, uterus,
vaginal openings

Respiration, 12, 31, 74

“Roundness,”’ 104-105

also
sem-
canal,
and

Sagittal sections, 140-150, 178-188, 190-
196, 220- 239, 268

Salivary gland, see gland L

Schmalhausen’s formula, 107-109

Scolopoides, 55, 63-64

Second thoracie leg, 14, 39-41, 50, SO,
84, 94-95, 98-100, 112-114, 244

Secondary setae, 18, 22, 34

Secretion of shell, 71-73

Selvage, 65, 66, 67

groove, 66

strip, 65-66
Seminal receptacle, 45, 74, 76, 77
Sense club, 8, 22, 24, 96, 236
Setae, 3, S, 16 dels, 19. 20, 2). 22

24, 26, 34, 35, 36, 38, 39, 40, 43,
44, 47, 55, 58, 63, 83, 84, 96- 100
“Shell gland,” see excretory gland B
Sperm, 74, 77,
Spiral canal, 74, 76
“Stick,” 45, 77
Stomach, 15, 50, 54, 57, 58, 60, 75, 96
Subdermal cells, 54, 63

Supporting fibers, 63
Swimming, 4, 8, 16, 19, 83
Synapsis, 75

Syneytium of ovary, 75
Syngamic reproduction, 7 77, 78
Synizesis, 75

Tapetum, 48
Teeth of mandibles, 24, 25, 29, 240, 246
Terminal filament of scolopoide, 64
the masticatory pracess, 35
Third thoracie leg, 14, 34, 41-45, 80,
94-95, 99-100, 112-113, 246
Thompson’s graphic expression of
growth gradients, 107
Thoracic legs, 4, 12, 14, 36, 60
first, 12, 14, 15, 32, 33, 34,°36-39441-
50, 56, 57, 94-95, 244, 246, 268
second, 14, 39-41, 50, 80, 84, 94-95,
98-100, 112-114, 244
third, 14, 34, 41-45, 80,
100, 112-113, 246
Thorax, 4, 12
Tolerance, cold, 85-87
heat, 85-86
of egg, 79-80
pH, 84-85
Trabecular processes, 51, 63
Transverse sections, 152-166, 206-218
270-282, 284-290, 292-302, 304-
314, 316-318
Tritocerebrum, 23, 24, 59-60

94-95, 99-

)

Upper lip, 4, 8, 15, 20, 27-29, 53, 57,
58, 63
Uterine openings s, 15, 45, 46, 47

Uterus, 46, 57, 74, 75, 5, 77, 80, 81, 100

Vaginal openings 7

Valves, 15, 60- 61, 64- 65, 80, 82, 83,
110- 114, 258, 260

Variations, in shape of instars,

in size of instars, 101- we

Ventral chain of gangha, 27, 31, 36, :
41, 45, 47, 48, 49, see

Ventral duplicature, 58

Vestibule, 66

105-109

Walking, 4, 8, 14, 16, 19, 20, 39, 84

X-ray diffraction, 67-70

Y-shaped process, 28, 58

[ 324 ]

ere, val VIII
of ae, With 26 plates. By F.S. Stickney. $2.00.
m Certain Features of Nematodes and Their Significance. With
Hetherington. $1.00.
ritish Guiana and a With 19 plates. By F. 1 Stevens.

Ripley. $1. 25

A - Vol. IX
US Glands of Lumbricidae and Diplocardia. With 12 plates. By Frank

1c aad ‘Taxonomic ide of the pee iieas With 27 ae and 9 text-
s. By R. Kudo. $3.00.

Me ie Vol. X
son the Avian pee of the Cestode oo Hymenolepididae. With 9 plates

: yee W. Manter. $1. 50.
om aM Ww Studies on Furcocercous Cecene With 8 plates and 2 text-figures. By

Vol. XII
M Cee Studies of the Genus Cercospora. With 4 plates. By W. G. Solheim.
$1.00.
rphology, Taxonomy, and Biology of Larval Scarabaeoidea. With 15 plates. By
W. P. Hayes. $1.25.
sawflies of the Sub-family Dolerinae of America North: of Mexico. With 6 plates.
Ag > By H. H. Ross. $1.25.
A pa of Fresh-water Plankton Communities. By Samuel Eddy. $1.00.

Vol. XIII
i Studies on Some Protozoan Parasites of Fishes of Illinois. With 8 plates. By R. R.
Kudo. 75 cts.
The Papillose Allocreadiidae: A Study of Their Vcishology, Life Histories, and
Relationships. With 4 plates and 6 text-figures. By 5. H. Hopkins. $1.00.
olution of Foliar Types, Dwarf Shoots, and Cone Scales of Pinus. With 32 text-
figures. By C. C. Doak. $1.50.
Monographic Rearrangement of Lophodermium. With 5 plates. By L. R. Tehon.

[Continued on back cover]

ILLINOIS BIOLOGICAL MONOGRAPHS

(Continued from inside back cover) —

Vol. XIV

No. 1. Development of the Pectoral Limb of Necturus maculosus

Chen. $1.00. tate
No. 2. Studies on North American Cercariae. With 8 plates. By Hae
No. 3. Studies on the peng a and Life aly of ame in t

9 piawice By H. J. Bennett. $1. 50.
Vol. XV

No. 1. Experimental Fides on Héhinostoma revolutum (Proce) Ay
Mammals. With 3 plates. By Pee, Beaver. $1.00. Bey

By W. C. Van Deventer. $1.00. ;
No, 4. Taxonomic Studies on the Mouth Parts of Larval Anura, With 4
By R. J. Nichols. $1.00.

Vol. XVI

Nos. 1-2. The Turtles of Ilinois. With 31 plates, 20 maps, Shek 15 text gu
$3.00. ;

No. 3. The Phylogeny of the Hemiptera, Based on a Study of the Hea
plates. By C. 8. Spooner. $1.00. \

No. 4. A Classification of the Larvae and Puparia of the Syrphidae ‘of ili ]
Aquatic Forms. With 17 plates. By Elizabeth M. ae v}

Vol. XVIL ee
No. 1. Comparative Studies on Trematodes (Gyrodactyloidea) fro:
American Fresh-water Fishes. With 5 plates. By J. D. Mize

No. 23, The Branchiobdellidae (Oligochaeta). of North Rae Crayfishes
By C. J. Goodnight. $1.00.
No. 4. Gyiplozical Observations on’ Endamoeba blattae. 8 plates. By P. Y

be XVII

With 6 plates and 2 ee By Vidi: Seance 75 Ga s

No. 3. Territorial and Mating Behavior of the House Wren. With 32 figures.
deigh. $1.50. ah

No. 4. The Morphology, Taxonomy, and Bionomics of the Nemertean Genus C TC i
tes. With 4 plates and 1 map. By A. G. Humes. $1.50.

Vol. XIX

Nos. 1-2. The Ostracods of Illinois—Their Biology and Taxonomy. With 9 plates By
Hoff. $2.50

No. 3. The Genus Conotrachelus Dejean (Coleoptera, Carcass in the North (
United States. With 9 plates. By H. F. Schoof. $1.50. UD Ne

No. 4. The Embryology of Larix. With 86 figures. By J. M. Schopf. $1.50.

Vol. XX

No. 1. Morphology and Development of Nosema notabilis Kudo! tenis in ‘ Sehnene
polymorpha Davis, a Parasite of Opsanus tau and. O. beta. ida 12, Ph
7 text-figures. By R. R. Kudo. $1.25. tak
No. 2. American Species of Amelanchier. With 23 plates and 14 maps. By G. N. Hones SI
No. 3. Minimum Areas for Different Vegetations: Their Determination from. Species-Ai
Curves. By A. G. Vestal. $1.50. Bp:
No. 4. Morphology and Phylogeny of Auchenorhynchous Homoptera, By Sol Kremer.
6 charts, 23 plates. $1.50. . ny

Epi an ny
Mb Nve a ig
A. of ati

Wi
ni
=

ff 4

ri
\
i
' @ ite
-
aay
“ }
-
i
\ *
{
‘ {
<

mir 1

~
‘

VERSITY OF ILLINOIS-URBANA

I

3 0112 05734