KC^ -A -ao»2-
Copu X
HARVARD UNIVERSITY
LIBRARY
OF THE
Museum of Comparative Zoology
1
DEPOSITED IN
THE LIBRARY OF
THE HIOI.OGICAL LABORATORIES
MUS. COMP. ZOOL. LIBRARY
JUL 26 1967
HARVARD UNIVERSITY.
MCZ 48 90
memoirs of t^& iPuseum of Comjjaratibe ^oologs
AT HARVARD COLLEGE. Vol. IX. No. 2.
SELECTIONS
FROM
EMBRYOLOGICAL MONOGRAPHS.
COMPILED BY
ALEXANDER AGASSIZ, WALTER FAXON, and E. L. MARK.
II.-ECHINODERMATA.
By, ALEXANDER AGASSIZ.
WITH FIFTEEN PLATES.
^^!<i(
CAMBRIDGE: •
Pn'nteti for tfjc fHuacum. July, 1883.
HUmoirs oi tlj« puscunt of Comgaratibe ^wolajgij
AT HARVARD COLLEGE. Vol. IX. No. 2.
SELECTIONS
FROM
EMBRYOLOGICAL MOiNOGRAPHS.
COMPILED BY
ALEXANDER AGASSIZ, WALTER FAXON, and E. L. MARK.
II.-ECHINODERMATA.
By ALEXANDER AGASSIZ.
WITH FIFTEEN PLATES.
CAMBRIDaE:
Pn'nteli for ti^e fHuseum. July, 1883.
H^'''A
MUS. COMP. ZOOL. LIBRARY
JUL 26 1967
HARVARD UNIVERSITY
N 0 T I C E
The Bibliograpby of tlie Eeliinodermata, by A. Agassiz, to accompanj' the second part of the " Selections from Embryological Monographs," has been publislied as No. 2 of Vol. X. of the Bulletin of the Museum.
The Bibliography of the First Part, the Crustacea, by Walter Faxon, forms No. G of Vol. IX. of the Bulletin of the Museum. Tiie Plates have been published as No. 1 of Vol. IX. of the Memoirs of the Museum.
Otlier Parts of the Bibliography and of the Plates are in preparation, — Protozoa, Acalephs, Polyps, Fishes, and Reptiles.
ALEXANDER AGASSIZ.
Museum of Compauative Zoology, Cambridge, Mass., U. S. A.
July, 1883.
TABLE OF CONTENTS.
Plates I., 11. Development o/Crinoiuea [Comalula). Figures from George J. Allman, William B. Car-
PENTER, A. GOETTE, HUBERT LUDWIG, and C. WyVILLE THOMSON.
From Wyvillk Thomson. " A. Goette. " AYyville Thomson. " W.m. B. Carpenter. " Geo. J. Allman
" H. LuDWIG.
|
te I. - |
- 1-9 |
Cuhiatiila. rosacea |
|
10-26 |
Comatula mcditerranea |
|
|
27-35 |
Comatula rosacea |
|
|
te II. |
— 1-17 |
Comatula rosacea |
|
17-21 |
Comatula rosacea |
|
|
22-23 |
Antedoih larva . |
Plates III., IV. Development o/Ophiuroidea. Figures from Alexander Agas.siz, N. C. Apostolid^s, August Krohn, Hubert Ludwig, Elia.s Metschnikofp, Johannes MiiLiBR, Max Schultze, and T. H. Stewart.
Plate III. — 1-14 Aniphiura squamata
14'-19
20 Ophiopholis !
21-23 Amphiura ?
24, 25 Opliiocoma rosula .
20-31 Amphiura squamata,
32, 33 Viviparous Ophiuran
Plate IV. — 1-13 OpMothrix versicolor
14-26 Ophiothrix fragilis .
27-34 PliUeus bimaculatus
From E. Metsciinikoff.
" H. Ludwig.
" Alexander Agassiz.
( C It i .'
" T. H. Stewart.
" Max Schultze.
" A. KUOHN.
" N". C. Apostulid^s.
" Johannes Muller.
Plates V.-VIII. Dcvelojmunt of Asteroidea. Figures from Alexander Agassiz, Louis Agassiz, Wilhelm BuscH, J. Koren and D. C. Danielssen, S. Loven, Hubert Ludwig, Johanne.s Muller, Michael Sars, and C. Wtville Thomson.
Plate V. -
Plate VI.-
Plate VII. -
Plate VIII.
1-4 Echinaster scpositns
5-49 Asterina gibhosa
1-11 Asterina gibhosa (continueil)
12-19 Astcracanthion flaeciila .
20-23 Ptcraster 7nilitaris .
24-32 Asteracaiithion violaceus
33-42 Eclmiastcr sanguinolcntiis .
43-46 Echinaster Sarsii
47, 48 IVurmfirmigc Aslerie
49-51 Ptcraster militaris
- 1-28 Astcracanthimi bcrylinus
29-34 Asteracanthion paUidns
— 1-23 Asteracanthion pallidus (I'ontiniicd)
24 Bipiinnaria aslerigera .
25-26 Asterias glacialis . . .
From W. Buscii.
" H. Ludwig.
" L. Agassiz.
" M. SAR.S.
" Wyville Thomson.
" M. Sars.
" Johannes Mi) i.i.ER. (( <( '1
" J. Koren and D. C. Danielsen.
" Alexander Agassiz.
Johannes Muller. S. Loven.
TABLE OF CONTENTS.
Platks IX.-XII. Develupment of Eciiinoidea. Figures IVnm Alexander Ar.ASSiz, Wilhelm Busch, J. W.
From E. Selenka.
W. BlTSCH.
Johannes Muller.
J. W. Fewkes.
Alexander Aoassiz.
H. Garman and B. P. Colton.
Alexander Agassiz.
A. Krohn.
Johannes JIuller.
Alexander Agassiz. Johannes Muller.
From .\lexander Agassiz.
|
Fewkes, H. |
"1 arm Ah |
and B. P. Colton, Aigust kRoH.v, Joi |
|
PL.vrE I.X.- |
- 1-16 |
Echinus miliaris |
|
17-19 |
Strongyloccntrolus lividas |
|
|
20-23 |
Arbacui puslulosa . |
|
|
24-27 |
Eckinocardium cordatum |
|
|
28, 29 |
Arbacia pustiilom . ' . |
|
|
30-37 |
Arbacia piislidosa |
|
|
38-40 |
Arbacia punctulata . |
|
|
41 |
Arbacia jmnclulata |
|
|
42, 43 |
Arbacia punctulata |
|
|
44, 45 |
Arbacia punctulata |
|
|
Plate X. — |
1-44 |
Slrongyloccntrotus Drobachieusis |
|
Plate XI. - |
-1, 3, 5 |
Spalangiis purpurcus |
|
2 |
4, 6-9 |
Spatangus purjmreus |
|
10 |
Spatangoid Phiteus |
|
|
11 |
Echinoid Pluteus |
|
|
12-18 |
Echimis lividus .... |
|
|
19-27 |
Echinocyamus jiusillus ? |
|
|
28 |
Ecliiiiarachnius parma? |
|
|
29 |
Echinus acutus |
|
|
30 |
Echinus brevispinosus . |
|
|
Plate XII. |
— Young Stages of Echini. |
|
|
1-3 |
Gonioeidaris canaliculata . |
|
|
• |
4 |
Dnrocidai-is papillata . |
|
5,6 |
Aslhenosoma hystrkc |
|
|
7 |
Diadema setosum |
|
|
8-12 |
Mcllita sexforis |
|
|
13,14 |
Mcllita tesludinata |
|
|
15, 16 |
Mcllita lo7i.gifissa |
|
|
17-22 |
Eckinarachnius parma . |
|
|
23,24 |
Encopc emarginata . |
|
|
26-29 |
Conolampas Sigshci |
|
|
30 |
Ilcmiastcr cavernosas |
|
|
31-35 |
Hcmiaster cavcrnosus . |
|
|
36, 36' |
Spatangus purpureus |
|
|
37-40 |
Brissopsis lyri/era |
Wyville Thomson. Alexander Agas.siz.
Plates XIII.-.W. Development of HoLOTurnoiPMA. Figures from D. C. Danielssen and J. Koren, Elias Metschnikoff, Johannes Muller, and Emil Selenka.
Plate .\ 1 1 1. — 1-11 Synapta — Auricularia with calcareous vhech Fr
12-17 Synapta (continued)
18 Auricularia wilh calcareous gland .
19 Auricularia with eleven spheres 20-32 Atiricularia with clastic spheres 33-37 Auricularia with dendritic anal gland .
YhATEWV.— 1-12 ffolothuriatubulosa
1 3-27 Jlolothuria tremula
Plate XV. — 1-13 Cucumaria doliolum
14-27 Homologies of Echinoderm Larvae .
om Johannes Muller. E. Metschnikoff. Johannes Muller.
E. Selenka.
D. C. Danielssen and J. Kouen.
E. Selenka. Johannes Muller.
TABLE OF CONTENTS.
REFERENCES TO THE PRINCIPAL FIGURES.
For a comparison of the earliest stages of development, see the Segmentation uf the Eijej on
* Mate I. figs. 1-4, for Comatula. Plate III. figs. 1, 26, Plate IV. figs. 1-7, for the Ophiiiroidea (Amphiura and Opliiothi-ix). Plate V. figs. 6-11, Plate VII. figs. 1-12, for the Asteroidea (Asterina and Asteracantliion). Plate IX. figs. 1, 2, 17-20, Plate X. figs. 1-13, for the Echinoidea (Arbacia, Echinus, and Strongylocentrotus). Plate XIV. fifs. 1-3, Plate XV. figs. 1-3, for the llulothuroidea (Holothuria and Cucuniaria).
For the Formation of the Blaslula and Oastrula, see
Plate I. figs. 5, 11, 12, for Comatula.
Plate III. figs. 3-7, Plate IV. figs. 8-10, for the Ophiuroidea (Amphiura and Ophiothrix).
Plate V. fics. 12-25, Plate VII. figs. 12-20, for the Asteroidea (Asterina and Asteracanthion).
Plate IX. fics. 3-12, 19-27, Plate X. figs. 14-24, for the Echinoidea (Arbacia, Echinus, Spatangus, Eohinocar-
dium, and .Strongylocentrotus). Plate XIII. fig. 12, Plate XIV. figs. 3-.5, Plate XV. figs. 3-6, for the Holotlmroidea (Synapta, Holothuria,
and Cucumaria).
For the General Homologies of Eehinoderm Larva, see Plate XV. figs. 14-27.
For the Development of the different External Parts of the Plutcus or Larva, see Plate I. figs. 8, 9, 21, 27, 28, for Comatula.
Plate III. figs. 9-14, 29, 30, Plate IV. figs. 11-19, for the Ophiuroidea. Plate V. figs. 1-3, 37-41, 44, 4.5, 47, 48, Plate VI. figs. 4, 12, 14, 16, 18, 24-31, 35-40, 44-46, Plate VII.
figs. 19-34, for the Asteroidea (Asterina, Echiuaster, and A.steracanthion). Plate IX. figs. 13-16, 30-35, 38-41, Plate X. figs. 26-37, Plate XI. figs. 1-17, 19-24, 28-30, for the Echinoidea
(Arbacia, Strongylocentrotus, Echinus, Echinocyanuis ? and Echinarachnius ?). Plate XIII. figs. 1-8, 13-16, 18-27, 33-35, Plate XIV. figs. 4, 8, 9, 15-20, Plate XV. figs. 8-11, for the
Holothuroidea (Synapta, Holothuria, and Cucumaria).
For the Development of the Water System of the Vasoperitmieal Sacs, see
Plate I. figs. 12-20, 22-24, for Comatula.
Plate III. figs. 6-14, Plate IV. figs. 18-20, 27, 29, 31, for the Ophiuroidea (Amphiura and Ophiothrix).
Plate V. figs. 20-28, 32-34, 36, 38, 43, 46, 49, Plate VI. figs. 2, 3, 6-9, Plate VII. figs. 20-34, Plate VIII. figs. 4-9, 11, 13, 14, 17, 18, for the Asteroidea (Asterina and Asteracanthion).
Plate IX. figs. 5-13, 19, 21, 26, 27, Plate X. figs. 21-37, for the Echinoidea (Arbacia, Echinus, Spatangus, Echinocardium, and Strongylocentrotus).
Plate XIII. figs. 4-37, Plate XIV. figs. 5-12, 17, 18, 21-27, Plate XV. figs. 6, 7, 9, for the Holothuroidea (Syn- apta, Holothuria, and Cucumaria).
For the Development of the Young Eehinoderm, see Plate I. figs. 24, 25, 29-36, Plate II. figs. 1-23, for Comatula.
Plate III. figs. 14-20, 22-25, 29-33, Plate IV. figs. 20-34, for the Ophiuroulea (Amphiura and Ophiothrix). Plate V. figs. 3, 4, 29-31, 35, 37-41, 45, 47-49, Plate VI. figs. 1, 4, 5, 9, 11, 13, 17, 19, 20-22, 29-32, 37-42,
47-51, Plate VIII. fig.s. 1-26, for the Asteroidea (Asterin.a, Echinaster, Pteraster, and Asteracanthion). Plate IX. figs. 35-37, 42-45, Plate X. figs. 37, 40-43, Plate XI. figs. 8, 17, 18, 2,5-27, Plate XII. figs. 30-34,
for the Echinoidea (.Vrbacia, Strongylocentrotus, Echinus, Eehinocyamus ? and Hemiaster). Plate XIII. figs. 6-11, 20-37, Plate XIV. figs. 17-27, Plate XV. figs. 8-11, for the Holothuroidea (Synapta,
Holothuria, and Cucumaria).
8 TABLE OF CONTENTS.
For the Young Stages of Echinoderms, see Plate I. tigs. 31, 34, 35, 36, Plate II. figs. 1, 3-7, 18-20, for Comatiila. Plate 111. ligs. 14'-20, 24, 25, 31, 32, Plate IV. figs. 24, 26, 32, 34, for the Ophiuroidea (Aiiiphiura and Ophi-
othrLx). Plate X. fig. 4, Plate VI. figs. 4, 5, 9, 10, 13, 15, 17, 19, 20-22, 31, 32, 42, 47, 48, 50, 51, Plate VIII. figs. 8,
10-12, 15-18, 25-28, for the Asteroidea (Asterina, Echinaster, Asteracauthion, and Pteraster). Plate IX. figs. 36, 37, 44, 45, Plate X. figs. 40-44, Plate XI. figs. 26, 27, Plate XII. figs. 1-40, for the
Eehinoidea (Arbacia, Stroiigyloceiitrotus, Ecliinus, Doroeidaris, Goniocidarls, Asthenosoma, Diadema,
Jtellita, Echinoeyamus, Encope, Echinarachnius, Conolanipas, Spatangus. and Hemiaster). Plate XIII. figs. 9-11, 29-31, 35-37; Plate XIV. figs. 21-27, Plate XV. figs. 10, 11, for the Holothuroidea
(Synapta, Holothuria, and Cucumaria).
EMBEYOLOGICAL MONOGRAPHS.
PLATE I.
Development of Crixoidea (Comatula).
Figures from C.
GOETTE.
'Wyville Thomson and Alexander
1-9. Comatula, rosacea. From C. Wyville Thomson, On the Erabryogeny of Aatcdon rosacens Linck (Coma- tula rosacea of Lamark), 1863. Trans. R. S. London, CLV., 1S65, Pis. XXIII. -XXVII.
10- 26. Comatula medilcrranea. From Alexander Goette, Vergleicliemle Entwickclungsgeschiclite der Coma- tula mediterranea, 1876, Pis. XXXV., X.XXVI. Archiv fiir Mieroskop. Anat., XII.
27 -35. Comatula rosacea. From C. Wyville Thomson, On the Embryogeny of Antedon rosaceus, quoted above.
1-9. Comatula rosacea. From C. Wyville Thomson.
1. Egg shortly after impregnation.
2, 3, 4, 5. Different st.iges of segmentation.
6, 7. Development of the pseudembryo within the vitelline membrane.
8, 9. Dorsal and ventral aspects of the pseudembryo sliortly before the disappearance of the ciliated bands.
10-26. Comatula medilcrranea. From A. Goette,
Oral funnel.
Perisome.
Circular canal.
Plight peritoneal sac (aboral body cavity. )
Continuation of the same into tVie stem.
.Stem of the young Comatula larva.
Skeleton of the stem.
Contractile tentacle.
Non-contractile (rigid) tentacles.
Visceral plate.
Its continuation between the intestine and the
water-system. Water-system. Stone canal. Cords of vibratile cilia;
10. Median section through a young larva (gastrula form).
11. Median section through a somewhat older larva.
12-15. Frontal sections of successively older larvip, seen from the dorsal side.
16. Transverse section of a similar larva, anterior plane.
17, 13. Sagittal sections; the median section is indicated in outline.
19. Median sections of a somewhat older larva.
20. Frontal section, seen from the ventral side ; the perisome begins to be intimately united with the outer skin
and the parietal plate.
|
a a. |
Gastrula axis. |
ot. |
|
o.f. |
Anus. |
P- |
|
bb. |
Longitudinal axis of the gastrula. |
r. |
|
c. |
Gastrula mouth. |
rp. |
|
d. |
Intestine. |
rp'. |
|
di. |
Qisophagus. |
St. |
|
/• |
Base of the stem of the Comatula larva. |
St'. |
|
f- |
Plate of base of stem. |
tt. |
|
Ip. |
Left peritoneal sac (oral body cavity). |
tt'. |
|
Ip'. |
Oral chamber. |
vs. |
|
m. |
Mouth. |
vs'. |
|
md. |
Mesoderm. |
|
|
mt. |
Mesentery. |
w. |
|
oh. |
Outer skin. |
■we. |
|
Ob'. |
Yellow cells of the same. |
wp. |
10 EMBRYOLOGICAL MONOGRAPHS.
•21. A larva at the time wlic-ii tlie skclfton begins to form ; the diagonally transverse dark stripe running across the
digestive cavity indicates the position of the mesentery. 22, 23. Sagittal section of a young embryo with a stem.
24. Frontal section of a similar larva ; the two layers of the rudimentary ring canal and tentacles begin to separate.
25. Median section of a mucli older embryo, with a comparatively longer stem. 2, hood of the oral anterior
chamber.
26. Ti-ansverse section of a larva perhaps slightly older, anterior plane.
27-35. Comatula rosacea. From C. "VVyville Thomson.
27. Dorsal view of a pseudembryo about in the stage of fig. 9.
28. Lateral view of a pseudembryo somewhat older than the preceding figure ; the ciliated bands are disappearing.
29. The pseudembryo is losing its special organs of assimilation and locomotion, and is passing into the Pentacri-
noid stage.
30. The youngest Pentacrinoid stage.
31. Pentacrinoid lai-va immediately after the complete separation of the oral valves, expanded.
32. A portion of the oral disk of the same stage seen from above, in a state of complete expansion ; a, patent oral
aperture bounded by a ring of contractile tissue, and showing yellow, richly ciliated granular folds, arranged somewhat spirally on the walls of the digestive cavity ; b, central ring of the radial vascular system ; c, rigid non-extensile tentacles in immediate connection with the vascular ring, ten in number, and laid up in a state of complete expansion in pairs against the inner surface of the oral valves, /; d, the first pair of exten- sile radial tentacles ; c, azygous radial extensile tentacle leading out of the growing arm to its bifurcation, and giving off pairs of tentacles of the .same series from its base.
33. Pentacrinoid in the same stage as fig. 31, the cup closed.
34. Pentacrinoid larva immediately before the expansion of the ventral disk ; a, centrodorsal plate ; b, series of basal
plates ; c, first radial i>lates ; d, second radial joint ; c, third radial ; /, first brachial joint ; rj, anal plate ; h, stem joint ; k, cribriform plate supporting the disk of attachment ; I, gi-anular visceral mass ; m, ccecal process pas.sing from the stomach towards the papilla which indicates the position subsequently occupied by the anal tube ; n, oral valve and plate.
35. Another Pentacrinoid larva in a somewhat eariier stage than the preceding, expanded, and showing the
arrangement of the non-extensile tentacles in connection with the oral vascular ring.
MEM. M. C. Z., IX. No. 2. — ECHINODEEMATA. 11
|
a. |
Anal plate. |
|
bb. |
Basals. |
|
br. |
Brachials. |
|
c. |
Cirri. |
|
c'. |
Central pore. |
PLATE II.
Development of CmsowEA (Comatula), continued. Figures from William B. Carpenter, George
J. Allman, mid Hubert Ludwig.
1-17. Comatida rosacea, continued. From William B. Carpenter, Researches on the Structure, Physiology, and Development of Antedou (Comatula Lamk. ) rosaceus. Part I., 1866. Trans. K. S. London, CLVI., 1866, Pis. XXXIX.-XLII.
c d. Centrodorsal plate.
0 0. Oral plates.
r^, r^, r^. First, second, and third radials.
V. Vent.
1. Greatly enlarged view of a Pentacrinoid larva, in a stage nearly corresponding with that of fig. 7, the nearest
ray having heen removed so as to bring into view the oral apparatus : cd, centrodorsal plate bearing two cirri, one rudimentary, the other, c, in an advanced stage of development ; r^ r-, r^, first, second, and third radials ; o o, orals, now completely separated from the radials by the intervention of a membra- nous perisome.
2. Calyx of the same specimen, seen from the other side, showing the centrodorsal plate bearing two cirri, one
rudimentary, the other, c, still retaining its rudimentary form ; the first, second, and tliird radials, r' )•', r^ }-2, r" c', and the anal plate, a, are now lifted out from between the first i-adials by the development of the prominent vent, v, to which it is attached. 3, 4, 5, 6, 7. Pentacrinoidal larvae in different stages. Figs. 4-7 are the successive stages preceding the fully developed Pentacrinoid stage, fig. 3.
3. Shows the Pentacrinoid ready to assume its free condition, two rows of dorsal cirri being now completed, the
arms being considerably elongated by the addition of new segments, and several pairs of pinnules being formed at their extremities.
4. Shows the basal, h b, the circlet of first radials, r' >■', already complete, the rudimentary second and third radi-
als supported by this and the circlet of orals, o o, alternating with these and resting on the first radials.
5. Shows the incipient development of the arms from the extremities of the third radials, the relative position of
the other parts being but little changed, and the dorsal cirri not having yet made their appearance. See fig. 10 for a representation of the skeleton in this stage on a larger scale.
6. Showing the further development of the arms, the incipient opening out of the calyx occasioned by the
increased development of the first radials, and the first appearance of the dorsal cim.
7. Showing the first appearance of the pinnules at the extremities of the arms, the further opening out of the
calyx, bringing the vent to view, and the formation of the first whorl of dorsal cirri.
8. Skeleton of an early Pentacrinoid larva, from a dried specimen, showing the mode in which the calyx can be
(in that stage) completely closed in by the folding together of the orals, o o.
9. Skeleton of the Pentacrinoid larva of fig. 3, showing two rudimentary segments of the stem, the incipient
development of the dorsal cirri, the basals, b h, the first, second, and third radials, and the anal, a, now being lifted up from between the first radials.
10. Skeleton of Pentacrinoid at the time of the first development of the arms, and before the first appearance of
the dorsal cirri ; bb, basals ; r' /■', first radials ; a, anal ; r- r-, second radials ; o o, orals; r^r*, third radials.
11. Skeleton of the calyx of a Pentacrinoid nearly ripe for detachment, as seen from its internal or ventral aspect,
the centrodorsal plate having been removed ; b b, ba.sals ; r^ )■', first radials.
1 2. The same as seen from its external or dorsal aspect ; c, central pore for the passage of the sarcodic axis through
the centrodorsal plate ; bb, basals ; r^ r^, first radials ; r'^, second radials ; ?■', third or a.xillary radials ; br, brachials; a, anal.
12 EMBr.YOLOGICAL ilOXOGlJAPHS.
13. Iiii-iiiimit rosette formed by the coalesceiu-e of tlie five altered basals in a young Antedon. 1-t. Skeleton of base of calyx of young Antedon, seen from its internal or ventral side ; showing the five basals (i) altered by endogenous growth in [ireiiaration for the formation of the rosette.
15. Skeleton of base of ealy.x of young Antedon seen from its dorsal aspect, the centi'odorsal plate having been
removed ; showing that the central space round b, on the under side, has been enlarged by the resorption of a part of the original basals, though it is still contracted, near the cavity of the cah-.x, by the secondary endogenous growth, with the same system of a.vial canals as are figured in the subsequent figure (fig. 16).
16. The same as fig. 15, seen from the ventral aspect ; showing the five basals grouped around J, and traversed
by canals for the radiating cords of the sarcodic axis, of which a trunk enters each basal from the central space, and then subdivides into two branches, that pass into the two radials between which the salient angle of the basal projects ; thus each first radial receives cords from two basals, and these are lodged in two canals which coalesce into one towards its distal border, each of them having first become connected by a lateral branch with the like canal in its contiguous first radial ; <— «— > shows the position of the anal.
17. Calyx of young Antedon just detached, seen from its dorsal side, showing five cirri of the mature type and
five of tlie rudimentaiy type, the radial and brachial plates, and the extension of the visceral disk as far as the third radial.
18-21. Comalala rosacea, conWnwii.. From George J. AUman, On a Prebrachial Stage in the Development of Co- matula and its Importance in Relation to certain Aberrant Forms of Extinct Crinoids (1863), PI. 13. Trans. R. S. Edinburgh, XXIII. Part II., 1864.
18. The animal with its roof-plates fully expanded and the cirri extended from between their edges.
19. Tlie same in the act of expansion.
20. The same with the cirri entirely withdrawn, and the roof-plates closed.
21. Outline of the body looking down upon it from the vertex.
22. 23. Antedon Larva. From H. Ludwig, Ueber den primaren Steinkanal der Crinoiden, nebst vergleichenden
anatomischen Bemerkungen iiber die Echinodermen iibcrhaupt, 1880, Pi. XII. Zeits. f. Wiss. Zool., XXXIV. Morpliol. .Studien an Echinodermen, II. Heft 1.
22. Optical longitudinal section of an Antedon larva, nr, mouth ; d', cesophagus ; d", stomach ; L l', body cav-
ity ; II, position of the so-called heart ; w, water-system ring ; s T, stone canal ; t, tentacle ; K, reddish- brown body ; F, axial cord of the stem.
23. Diagrammatic sketch of an Antedon larva, d'", intestine ; A, anus ; P, pore in calyx ; T, t', t", tentacles ;
other letters as in fig. 22.
MEM. M. C. Z., IX. No. 2. — ECHINODEEi\LA.TA. 13
PLATE III.
Develop77ieut of Opuwnoiviisk. Figures from li,hi\s Metschnikofp, Hubert Ludwig, Alexander Agassiz, T. H. Stewart, Max Schultze, and August Krohn.
(1-20, 26-33, Viviparous Ophiurans.)
1-14. AmpMura squamnla. From E. Metschiiikoff, Studien iiber die Eiitwickehmg der Echinoilei-mi:-ii und Nemertinen. Mem. de I'Acad. Imp. des Scien.de St. Pe'tersbourg, VIP Serie, XIV. No. 8, Hs. III. B, IV., 1869.
b I. Blastoderm. o. Mouth.
c. Cutis. 0 c. CEsojihagus.
: c. Provisional limestone rods ; probablj' the ho- p a. Dorsal pore of the water-system (madreporite).
mologue of the Pluteus rods. p I. Eemnant of rudimentary Pluteus.
cp I. The bilateral embryonic skeleton. t. Tentacles.
. c s. Segmental cavity. v. Kudimentary water-system.
d'. Left lateral disk. v a. Water-system.
d-. Plight lateral disk. v t. First trace of digestive cavity.
e})- Epidermis. vv. Lobed wjtter-system.
me. Thin outer membrane surrounding blastoderm. op,vr. Circular canal.
VI V. Thick inner membrane of same.
1. Egg, surrounded by its two membranes (m e, mv) with the blastoderm (b I).
2. The same in profile : the outer egg membrane is not figured.
3. Somewhat more advanced stage, showing, in addition to the blastoderm, the first indication of the digestive
cavity {vt) and of the large cells of the cutis (c).
4. Elongated embryo still protected by the inner egg membrane (m r). The deposition of the provisional lime-
stone rods has commenced {cc). On each side of the future cesophagus are placed the rudiments of the 'water-S3'stem (v).
5. Somewhat older embryo, with longer limestone rods {cp I), seen in profile.
6. Still older embryo, seen from the dorsal side, showing the greatly enlarged water-system (crOand its two
lateral disks (rfi, d-).
7. Somewhat older embryo, also seen from the dorsal side, showing the five lobes of the water-system {v a).
8. Older stage, remarkable for the great development of the lateral disks (rf', d-), the change in the position of
the digestive cavity and cesophagus, the great increase in the size of the lobes of the water-system (v v), and the formation of a dorsal pore {pa), the future madreporic body.
9. Somewhat older embryo, showing the horseshoe-shaped water-system, each primary fold of wliich {vv) has
subdivided into four secondary lobes.
10. Embryo seen in profile. The cesophagus is already surrounded by the water-system ; each fold of the water-
system has subdivided into five smaller ones. The stone canal is most distinct.
11. An embryo about in the stage of fig. 10, seen from the dorsal side : the provisional limestone skeleton is
already disappearing.
12. The water-system of the same embryo : v v, the blind sacs (tentacles) of the water-system ; v r, the circular
canal ; 2> c-, the madreporite.
13. The embryo in a stage immediately after passing from the bilateral to the pentngonal form, seen from the
actinal side ; the peculiar arrangement of the tentacles (0 and the formation of the mouth skeleton are specially to be noticed in this stage.
14. Somewhat more advanced than the preceding stage, seen from the dorsal side, showing the si.\ reticulated
plates of the abactinal surface, as well as the stem (p I), first described by Kiohn and Schultze, forming a temporary connection with the ovary. This becomes atrophied in still older stages.
14 EMBEYOLOGICAL MONOGRAPHS.
14'-19. Amphiura squamata. From Hubeit Lmlwig, Ziir Entwickelungsgeschicte des Ophiureiiskelettes, 1882 (Morphol. Studitu, II., Heft 2). Zeits. f. Wiss. Zool., XXXVI., PI. XI.
^1, ^2- First and second auibulacral plates. B a. Radials of the young ophiuran.
A d^ A d.,, A d3, etc. First, second, third, etc. ad- 7'. Tei-minal plates,
anibulacral plates. To. Torus angularis.
C. Dorsocentral plate. t. Teeth.
in. Madreporio i)late. V V- Ventral plates.
0. Oral plates (mouth shields). x. Remnant of embryonic skeleton. 11. Primary radials.
14'. Young .Vmpluura, seen from tin- dorjal side. The composition of the plates, of i/-sliaped rods, is still plainly visible.
15. Somewhat older stage, seen from the actinal side. V, oldest ventral plate ; P, very young ventral plate ;
t, rudimentary teeth.
16. Somewhat older tliau fig. 14', but younger than fig. 15, seen from the dorsal side.
17. Somewhat older than the stage corresponding to fig. 19, seen from the dorsal side, showing the arrangement
of the intermediate plates formed between the central and the primary radials.
18. Somewhat older than the stage of fig. 17, seen from the dorsal side ; the intermediate plates have greatly in-
creased in size and number. 18'. Shows the arrangement of the plates of the actinal side in a stage slightly older than fig. 17.
19. Stage corresponding to fig. 15, seen from the dorsal side ; intermediate plates begin to appear between the
central plates and the primary railials.
20-2.3. Ophioplwlis (?) and A.nphiara { !). From Alexander Agassiz, On the Embryology of Echinoderms. Mem.
Am. Acad., IX., figs. 29, 31-33, 1864.
20. Ophiopholiihc'Us> From a drawing made under the direction of L. Agassiz in 1849. Abactinal view of a
young Ophiopholis to show the arrangement of the plates of the disk. 21-23. Anijihiura?
21. A full-grown Plutens, in wliii-h the water-tubes, w, ?»', are plainly seen, d, digestive cavity ; m, mouth :
a, anus ; t, rudimentiu-y tentacular lobes of the water-system ; %■', anal, and t', oral vibratile cord ; c'-e*, arms of the Pluteus.
22. Older stage, seen from the abactinal side, in which the arms of the Pluteus (c"-c<) are almost entirely resorbed ;
the two long anns <•' are still intact, they are omitted for want of space, r, abactinal region ; ij, rudi- mentary terminal plate ; y', adambnlacral plate ; »-^, junction of limestone rods of the long arms c'.
23. The same, seen from the actinal side ; lettering as above : s, actinal region ; t, t!, tentacular loops.
24. 25. Ophiocorna rosula. From T. H. Stewart, On the Yonng State of Ophiocoma rosula, and on the Form and
Development of the Spines of this Species. Ann. k Mag. Nat. Hist., XVIII., 1856, PI. XV.
24. Young Ophiocoma seen from the abactinal side.
25. Actinal view of central portion of the disk.
26-31. Amphiura squamata. From Max Schultze, Ueber die Entwickelung von Ophioh-pis s(iuamata, einerleben- diggebaliri^nden Opldure. Arcliiv. f. Anat. Phys. u. Wiss. Med., 1S52, PI. I.
26. Ovarian eggs of Amphiura squamata.
27. Young embryo with rudiment.iry provisional limestone rods.
28. Somewhat oMerthan fig. 27, the embryonic limestone rods are arranged symmetrically.
29. Older embryo. In addition to the provisional limestone rods, a, we have also the radials, h, developed ; and
the first trace of the terminal plates, <-.
30. Tlie embryo has assumed a pentagonal outline ; of the provisional limestone rods we find only the remnants at
a ; lettering as before ; the plates of the abactinal side are seen through from the ventral side under the rudimentary actinal plates.
31. Portion of a yonng Amphiura measuring J'" in diameter, seen from the actinal side : a, interbrachial dorsal
plates ; h c, actinal plates adjoining actinostome ; d d, interbrachial plates of the actinal side ; c e, spoon- shaped brachial plates; /, tcnninal plates; g, g, tentacles ; h, teeth.
32. 33. Viviparoun Ophiuran. From August Krohn, Ueber einen neuen Entwickclungsmodus der Ophiuren.
Archiv. f. Anat. Phys. u. Wiss. Med., 1857, PI. XIV. B.
32. Actinal view of ophiuran embryo ; a, pentagonal disk of young ophiuran ; b, central cavity, the future
mouth ; c, tentacles ; rf, tentacles of actinostome ; c, remnant of rudimentary Pluteus.
33. Young ophiuran of same emliiyo ; a, dorsal plates ; b, arm plates ; c, terminal jdate ; d, spines of the actinal
side projecting beyond the disk.
MEM. M. C. Z, IX. No. 2. — ECHINODERMATA. 15
PLATE IV.
Development of Ophiuroidea, continued. Figures from Nicolas Christo ApostolidIis and
Johannes Muller.
1-13. OpJiiothrix versicolor. From N. C. .Apostolides, Anatomie et DeVeloiipement dcs Ophiures. Archives de
Zool. Exp et Gen., X., PI. XI., 1881.
1. Egg. m, outer envelope ; y, yolk ; r, geraiinative vesicle ; n, micleus.
2, 3, 4, 5. Different stages of segmentation.
6. Blastosphere.
7. Blastosphere. e, ectoderm cells.
8. Older than fig. 7. c, ectoderm; y, yolk cells.
9. Older stage ; lettering as before. First appearance of the limestone rods of the Pluteus.
10. .Still older stage ; r, tlie limestone rods of the Pluteus have increased in size.
11. .Slightly older ; the digestive cavity, d, is outlined.
12. The embryo assumes somewhat the Pluteus outline.
13. Young Pluteus seen from the dorsal side. ;), general cavity ; /, limestone rods ; a, anal region of the digest-
ive cavity.
14-26. OphiothrixfrnrilJh. From .1. Miiller, Ueber die Ophiurenlarven des Adriatisclien Heeres, Berlin (Pt. 5), (1851,) Pis. VI., VII., VIII. Abhand. d. K. Akad. d. Wiss., Berlin, 1852.
14-17. Younger stages of the Pluteus. m, moutli ; d, digestive cavity.
18. Pluteus at a stage in which all the arms are developed, although the two long arms have by no means reached
their full length (see fig. 19). ni, mouth ; o, ffisophagus; d, digestive cavity ; i', intestine ; w, u', lateral disks of water-tubes ; t, lobed water-system.
19. Pluteus of same, in which the two long arms have reached their full length : lettering as in fig. 18.
20. The long arms of the Pluteus alone remain (extremities omitted) ; the others have been mostly resorbed ; the
young ophiuran has assumed a pentagonal outline ; the plates of the abactinal system, the terminal aim plates, and the interbraehial plates, are represented by j/-shaped rods, t', tenninal lobes (tentacles) ; fi, actinal lobes ; fl, second i)air of lobes.
21. Pentagonal Ophiothrix, seen from the dors.il side : the teeth are seen through the disk.
22. The same as fig. 21, seen from the actinal side, the arms folded towards the aetinal opening, showing also the
hooks, the teeth, and the true mouth in the depth of the central star-shaped mouth.
23. Slightly older, seen in profile : the long arms of figs. 20-23 are still of full length.
24. A young Ophiothrix after the loss of the two long arras, seen from the dorsal side.
25. Somewliat older than stage of fig. 23, seen from the actinal side, t', fl, fi, fi, terminal, actinal, and second
and third pairs of tentacles.
26. Young Ophiothrix, seen from the abactinal side, with two arm-joints. All traces of the Pluteus have dis-
appeared.
27-34. Pluteus bimaculatus. From J. Miiller, ITeber die Ophiurenlarven des Adriatischen Meeres, Pis. IV., V.,
quoted above.
27. Shows the young ophiuran at the time when the arms of the Pluteus begin to be resorbed and the tentacular
lobes are arranged in a horseshoe shape round the actinostome ; lettering as in fig. 25.
28. Somewhat older stage, seen from the actinal side ; the young ophiuran has assumed a pentagonal outline ; the
tenninal arm plates and the interbraehial plates are well developed ; the actinal tentacles are bent in towards the centre of the actinostome.
29. Still older stage, also seen from the actinal side, with three pairs of tentacles.
30. Somewhat older stage, seen from the abactinal side ; the plates of the disk, the centrodorsal, radials, and
intermediates, are well developed.
16 EMBRYOLOGICAL MONOGKAPHS.
31. OKliT ophiiiraii soon from tlie actiiial side ; I', t^, ('-, P, tcniiii)al, ami first, second, and tliird pairs of ten-
tjicles.
32. Free oiiliiuraii witliout Pluteaii appendages, fislied up from the surface, i-u'" in diameter. Seen from the
dorsal side. The stages 27-31 all have the two long amis intact ; the other shorter arms are iu different stages of resorption ; sec figs. 27, 28, 30. The long arms are not figured for want of space.
33. A single arm of fig. 32, from the abactinal side.
34. The central part of the disk with a portion of the arm of the same from the actinal side, showing the teeth and
the mouth papilke. Neither Jliiller nor Metschnikofl' was able to determine the ophiuran which is devel- oped from PliUeus limaculatus. Miiller considered it at first to he OjyJiioIcpis sqimmata.
MEM. M. C. Z., IX. No. 2. — ECHINODEItMATA.
17
PLATE V.
Development of Asteroidea. Figures from Wilhelm Busch and Hubert Ludwig.
1-4. Echinaslcr sepositus. From W. Biisch, Beobachtungen iiber Anatoniie und Entwickeliing einiger Wirbel-
losen Seetbiere. Berlin, 1851, PI. XII.
1. Young pelagic embryo : o, body ; b b, so-called bracliiolarian appendages.
2. The .same embryo somewhat more advanced : a, the body where the future Starfish is developed ; b I, so-called
bracliiolarian appendages ; o, commencement of a third pair.
3. The young starfish has assumed a pentagonal outline ; the tentacles (6) of the disk are clearly indicated, and
the brachiolarian appendages have taken their maximum development on each side of the a.vis a.
4. The most advanced stage of the young Echinaster observed by ICrohn. The brachiolarian appendages are
reduced by resorption to mere rudiments, a ; b, older pair of tentacles ; d, odd terminal tentacles ; v, young- est pairs of tentacles ; /, actinal amliulacral furrow.
5 ~ 49. Asterina gihbosa. From 11.
|
A- |
First ambulacral plate. |
|
A.2. |
Second ambulacral plate. |
|
Bl. |
Blood system. |
|
0. |
Dorsocentral plate. |
|
D. |
Digestive cavity. |
|
EC. |
Enteroccelum. |
|
Ed. |
Ectoderm. |
|
Eh. |
Egg membrane. |
|
Ent. |
Entoderm. |
|
Gin.. |
Gastrula mouth. |
|
HC. |
Hydroccelum. |
|
JRv |
JR.2, JEs, JH^, JH^. First |
|
I El. |
Left enteroccelum pouch. |
|
Lm. |
Larval mouth. |
Ludwig, Morphologische Studieu an Echinodermen, II., 2 Heft, 1882. Zeits. f. Wiss. Zool., XXXVII., Pis. L-VI.
L s. Larval ccsophagus.
M. Mesentery.
Ms. Mesoderm.
P. Dorsal pore.
r El . Right euterocadum pouch.
?!, T^, T3, T^, T^. First to fifth terminal plates.
1, 2, 3, 4, 5, denote the Hydroccelum lobes and am- bulacral arm lobes.
/, II, 111, IV, V, denote the antiambulacral arm lobes; 0 denotes the upper side of the embryo or larva ; U, the lower ; H, the posterior, and V, the anterior extremity ; L, left ; R, right; V L, in front to the left; H U, behind and below.
First to fifth Interradial.
5-10. Stages of segmentation of the first day.
5. Three spheres of segmentation are shown. I, I, are formed from the division of the u]iper of the two spheres ;
II, the lower sphere ; this is originally somewhat larger than the upper sphere.
6. The lower .sphere, II, is now also divided into two, IIj . . . .
7. The same as fig. 6, so turned as to show the two spheres Ij . . . .
8. The stage with four spheres somewhat older than the preceding figures.
9. A stage with eight spheres ; I2 and II2, the two splieres resulting from the division of the spheres I ami II
of the stage of fig. 8.
10. Stage with sixteen spheres, which have resulted from the subdivision of the cells \., into I3, and of the cells
II2 into II3.
11. Section through a blastula composed of 32 spheres.
12. Longitudinal section of a gastrula on the second day. Om, the gastrula mouth.
13. The same stage, looking into the gastrula mouth.
14. Longitudinal section of an older gastrula, with a decidedly narrower opening, Gm.
15. 16, 17. Posterior, anterior, and right view of an embryo just escaped from the egg, fourth day.
18. Longitudinal section of a gastrula somewhat older than fig. 14 ; the gastrula mouth is approaching the lower pole : a, the point at which the diverticula of the gastrula digestive cavity begin to be formed.
18 EMBRYOLOGICAL MONOGEArHS.
19. Gastrula three days old. The diverticulum of the gastrula cavity begins to be formed on the left and right
sides, a shows the left diverticulum.
20. Longitudinal section of a gastrula soon after its escape from the egg ; the left and right enterocojlum pouches
are indicated.
21. The same stage as fig. 20, seen from the left side : L m, the invagination of the ectoderm which eventually
forms the larval mouth.
22. The same stage a.s fig. 20, seen from the right side.
23. Embi-yo at the beginning of the fifth day, seen from the left, a, point of .separation of the gastrula cavity and
the enterocfelum ; b indicates the position of the gastrula mouth, Gm, which has now disappeared.
24. Transverse sei'tion of an embryo in the stage of fig. 23.
25. Longitudhial section of an embryo at the end of the fourth day : in which the g.a.strula cavity a is still in
communication with the enterocojlura. 2(i. Longitudinal section of an embryo at the end of the fifth day; the communication between the gastrula cavity and the enterocoelum has become completely shut olf at a.
27. Larva of the seventh day, seen from the left side ; the intestine, of which the position is merely indicated, has
been removeil, to show the mesentery, M, placed behind it. The arrow indicates the communication be- tween the enteroecelum of the larval organ and the enteroccelum surrounding the intestine.
28. Larva in the same stage as fig. 27, from the anterior side : the position of the intestine is only indicated.
29. 30, 31. Different views of a larva on the si.xtli day.
29. Seen from the left side : a, the larval organ (the brachiolarian appendages^ ; h, its anterior, c, its posterior
lobe ; d, the button-like projection on the creeping surface of the larval organ.
30. The same as fig. 29, seen from the anterior and left side.
31. The same, seen facing the creeping surface of the larval organ.
32. Larva of the sixth day, seen from the left. The hyuroccelum has become five-lobed, 1, 2, 3, 4, 5, its five lobes ;
the position of the mesentery on the other side of the digestive cavity is indicated as if seen through it. The arrows indicate the communication between the larval entcrociclum, the hydrocaduni, and the entero- ccelum surrounding the digestive cavity.
33. Larva of the seventh day. The'hydrocoelum is apparently shut off at a from the larval organ ; communica-
tion between it and the larval organ, however, is still clearly to be made out, and is indicated by the arrow ; b, formation of an ambulacral lobe (1) in the mesoderm below the hydrocoelum ; c, a band of con- nective tissue, not always found in this position.
34. Larva of the seventli day, from the posterior side. L s, the larval cesophagus ; .S's, pouch of the digestive
cavity extending towards the hydroccelum, which later trends towards the cesophagus of the young Starfish. The madreporic canal is abnormally early developed.
35. Exterior view of the satne larva, showing on an upper plane the dorsocential plate, C, with intcrradials
//ij, JRit JI's, JUi' JR^t and one of the terminal plates, T^ ; on the next somewhat lower plane are the terminal plates T-^, T.^, T^, and on a still lower plane, T.^.
36. Longitudinal section through the same larva, seen from the anterior side ; a shows the broad open communi-
cation between the enteroctclum of the larval organ and the hydroccelum, as well as the communication between the dorsal pore and the enteroccelum of the larval organ.
37. View of a whole embryo, seen from the right and lower side.
38. View of a larva partly cut open, seen from the right side. Bl", central blood system, a, mesoderm plate
covered by the entoderm of the enterocoelum ; this has taken the place of the larval cesophagus, which has now disappeared.
39. A larva of the eighth day, seen from the left side.
40. A similar larva, creeping, a and b in both these figures denote the anterior and posterior larval lobes.
41. The surface of the larval organ of an embrj'o somewhat more advanced than figs. 39, 40.
42. Larva in about the same stage as fig. 41, seen from the right side.
43. Larva on the eighth day, seen from the right side, showing the position of the blood c:ivity, Bl, in the mesen-
tery adjoining the fifth interradia], JI!^, in the position where the madreporic plate will eventually be formed.
44. Larva at the begiiming of the ninth day, seen from the left. 4,5. Larva at the end of the eighth day, seen from the anterior side.
46. Larva of the ninth day, cut open close to the surface on the left, to show the shape of the hydroccelum lobes,
their unequal development, and the formation of the first and second ambulacral plates.
47. Larva of the tenth day, seen from the anterior side.
48. The same, from the anterior and left side.
49. Larva of the tenth day. This larva still retains a large larval organ ; seen from the left, the section is so
made as to show the relation of the live lobes of the ambulacral and antiambulacral areas.
MEM. M. C. Z., IX. No. 2. — ECHINODERMATA.
19
PLATE VI.
Development of Asteroidea, continued. Figures from Hubert Ludwig, Louis Agassiz, Michael Sars, C. Wtville Thomson, Johannes Muller, and J. Koren and D. C. Danielssen.
1-11. Asterina gihhosa, continued. From H. Lmhvig, Morphologische Stiulicn an Echinodermen II., 2 Heft, 1882. Zeits. f. Wiss. Zool., XXXVII., Pis. VII., VIII.
Ai- First ambulacral jilate.
A.2- Second ambulacial plate.
A dy First adambulacral plate.
A 1I2. Second adambulacral plate.
Af. Anal opening.
£ I. Blood system.
C. Centrodorsal plate.
v. Digestive cavity.
Ec. Enteroccelum.
F. Terminal tentacle.
Fy First pair of tentacles.
F2- Second pair of tentacles.
ff c. Hydroccelum.
Ja. Interambulacral plates.
Jm. Intermediate plates.
3.
6
JH^, Jr..,, J Ih, JJ!i, J Ik- First to fifth interradial plates.
v]/ 1 . Interradial space of the larval organ.
■\f m. Interradial space of the madreporic plate.
M. Mesentery.
Afs. Mesoderm.
P. Dorsal pore.
S s. (Esophagus of Starfish.
St. Stone canal.
Ti, ^2, Ts, Ti, T'j. First to fifth terminal plates.
1, 2, 3, 4, 5, denote the hydrocrelum and ambula- cral lobes.
/, II, in, IV, V, denote the antianibnlacral arm- lobes. 0 denotes the up]ier extremity ; f", the lower ; V, the anterior ; //, the poste- rior ; L, left ; 1!, riglit.
11
1. Larva at the end of the ninth day, seen from the dorsal side of a young Starfisli. Tlie abactinal region is rep-
resented as transparent, to show the five lobes of the digestive cavity, the centrodorsal plate C, the five inter- radials JBj-J R^, and the five terminal plates Tj- 7 5. The remnant of the larval organ ( the brachiolarian arms) is represented by a.
2. Larva of tlie tentli day, seen from the anterior extremity ; the optical section passes through the lobes 1 and
3 of the hydroccelum ; a b, remnants of the larv.al organ.
Transverse section of a larva in the stage of fig. 2. Tlie amliulacral arm lobes 2 and 3 liave been cut longitudi- nally.
A yonng Starfish at the end of the tenth day, after the reduction of the larval organ rr ; the mouth of the Star- fish is not yet formed.
Young Starfish of the tenth day, seen from the abactinal side ; a, larval organ ; 4, 1, iiitcri-adial space of tlie larval organ ; i>tn, interradial siiace of the madrej5oric body.
Section across a young Starfish of the eleventh day, close to the actinal side. The water-ring is not yet closed ; at a are the two diverticula of the water system, which unite in a subsequent stage ; the section passes through the three-lobed digestive cavity, Ss ; this does not yet open externally.
7. Exterior view of the soft parts of an arm of a young Starfish, in the thirteenth day. iV, rudimentary nervous
ring ; B, swelling at the base of the terminal tentacle, where later an eye develops.
8. The same as fig. 7, to show the course of the ambulacral canal, the tentacles, and their position with respect
to the terminal, the amhuhicral, and the interradial plates.
9. Starfish of the sixteenth day, seen from the actinal side, to show the general arrangement of the hard parts.
0. .\ young Starfish of the sixteenth day, seen from the abactinal side, about in the same stage as fig. 9. Show- ing the arrangement of the plates of the abactinal side, the anal opening Af, the odd terminal tentacle F, extending beyond the edge of the disk ; .?, the young spines. Taken from a young Starfish forty-two days old. The abactinal surface is removed, .showing the five blind pouches of the alimentary canal, which begin to fork at the extremity to form the five pair of digestive coeca of the old Starfish ; M, rest of the larval mesentery ; Sj', the five interbrachial septa ; Bs, the inter- radial ececum of the end of the alimentaiy canal.
20 EMBRYOLOGICAL MOXOGEAPHS.
12-19. Asteracanthion flaccida. From dniwings made under the supervision of L. Agassiz, In 1848.
d. Abaetinal side of tlie young Starfish.
p. Larval organ (brachiolarian aiijiend.ages).
t. Terminal tentacles.
f, I", fi, I*. First, second, third, and fourth pair of tentacles, counting from the terminal tentacle.
12. I'rolile view of larva, with only the terminal tentacles developed.
13. The same as fig. 12, seen from the actinal side of the young Starfish.
14. Somewhat older stage than fig. 12 ; besides the terminal tentacles, t, an additional pair of tentacles, V, has
been developed.
15. The .same as fig. 14, seen from the actinal side.
16. Still older stage, with a second pair of tentacles, I', developed in addition to the t and (".
17. The same as figure 16, seen from the actinal side.
18. Still older stage ; the larval organ, p, is nearly resorbcd, and there are now in each arm four pairs of tentacles,
V-tS, in addition to the terminal tentacle, t. In figs. 14-19, ^'always denotes the last-formed tentacle, /" the last but one ; the outline of the young Starfish becomes more and more pentagonal as it passes through the stages of figs. 13 to 15, and 17.
19. The young Starfish has five well-formed arms, four pairs of tentacles, /'-/*, a distinct and closed circular water-
ring. The actinostome of the .Stai'fisli is not yet formed, and the larval organ has not been completely re- sorbed.
20-23. Pterastcr mililaris. From M. Sars, Oversigt af Morges Echinodernier, 1861, PI. VI.
a. The five perianal plates. d. Remnant of the larval organ.
b. Terminal arni-plates. c. Circular water-ring.
c. Second arm-plates. g. Terminal tentacle.
t', /", t"K Third, .second, and first pair of ambulacral tentacles.
20. Young Starfish, seen from the dorsal side ; a, the five perianal plates ; b, the ten arm-plates.
21. One of the arms, seen from the actinal side ; b, oldest arm-plates ; c, younger arm-jilates ; rf, remnant of larval
organ ; c, circular water-canal ; /, ambulacral canal ; g, terminal tentacle ; I', I", t'", third, second, and first pairs of ambulacral tentacles. The tentacles are contracted.
22. One of the arms, of a stage somewhat older than fig. 21, seen from the actinal side, with the tentacles extended.
23. Fig. 21, seen in profile.
24-32. Asteracanthioa violairns. From C. Wyville Thomson, On the Embryology of Asteracanthion violaceus, L. Quart. Journ. Microsc. Scieu., I., 1861, PI. VII.
24. Embryo about four hours after complete segmentation.
25. Embryo four hours later ; first formation of the larval organ, the so-called peduncle, or brachiolarian arms.
26. Embryo about nine hours later, with three brachiolarian appendages.
27. Embryo about twenty-four hours old.
28. Peduncle and appendages, which have become separated by a natural process of fission from an embryo about
a week old.
29. The embryo has become distinctly pentagonal ; the brachiolarian appendages are fully developed. Tliirty-si.'c
hours after segmentation.
30. Embryo in which the pentagonal outline of the yoimg Starfish is well defined, with five tentacles ; the brachi-
olarian appendages are beginning to be resorbed, and are no longer very efficient in assisting locomotion, as in the earlier stages. About eight days after segmentation.
31. Embryo five weeks after segmentation ; shows the remains of brachiolar appendages, much atrophied ; the ac-
tinostome of the young Starfish is indicated, and there are three pairs of tentacles in addition to the odd terminal one. 31'. Abactinal view of a young Starfish, about twelve days old, showing the arrangement of the limestone plates of that side.
32. View of the actinal surface to show the arrangi'ment of the aTiibulaeral plates.
33-42. Echinastcr sanguinnhntiis. From M. Sars, Ueber die Entwickelung der Seesterne. Fragment aus meinen Beitrage zur Fauna von Norvegen. Arcdiiv fiir Naturg., 1844, I., PI. VI.
a. Brachiolar ajipendages. b. Tubci'cular brai-hiolar appendage. c. Ambulacral tentacles.
33. Egg just laid, greatly magnified. Chorion colorless ; yolk, brilliant orange-red.
34. Egg three days old, in which the blastosphere has been formed.
35. Embryo just after being hatched.
MEM. M. C. Z., IX. No. 2. — ECHINODEEMATA. 21
36. Embryo in which the l.arral organs, a a, are foriiiing.
37. Soniewliat older embryo.
38. The young Starfish is well advanced : c, ambulacral tentacles ; the hrachiolarian appendages, a a, are fully
developed, and a small tubercle, b, has formed on the upper surface of the larval organ. Seen from the actinal side.
39. The same as fig. 38, seen I'rom the abactinal side.
40. Somewhat older stage, seen from the actinal side ; the young Starfish has now assumed a well-defined pentago-
nal outline.
41. The same embryo as fig. 40, seen from the abactinal side.
42. The same embryo, about two months old, seen from the abactinal side after the resorption of the larval organs.
43-46. Echinastcr Sarsii. From J. Miiller, Ueber den Allgemeinen Plan in der EntwiclceUing der Echinoder- men (Pt. 6), 1852, PI. I. Abhandl. der K. Akad. der Wiss. Berlin, IS53.
a. Larval organ, odd hrachiolarian arm. /. Interior cavity.
b. Larval organ, paired hrachiolarian arms. /'. Cavity leading to the brachiular appendages.
c. Tubercle between the hrachiolarian arms. g. Digestive cavity.
d. Cortical layei'. !i. Interior of the digestive cavity. c. Inner layer. i. Tentacles of the Starfish.
43. Longitudinal section through an embryo.
44. Transversely longitudinal section across the brachiolaiian arms.
45. Longitudinal sections of an older embryo in which the body cavity is divided into two, one of wliich contains
the digestive cavity, and the other communicates with the larval organs.
46. A similar section through an embryo somewhat older than fig. 45.
47. 48. Wurmforinige Asteric. From .1. Miiller, Ueber den Allgemeinen Plan in der Entwickelung der Echino-
dcrmcn (Pt. 6), 1852, PI. I. Quoted above.
a. Lateral ambulacral tentacles. b. Odd terminal tentacle. c. Spines of the actinal surface.
47. IVurmformige Astcric, seen from the abactinal side.
48. The same, seen from the actinal side.
49-51. Pteraster militaris. From J. Koren .and D. C. Danielssen, Observations sur le Developpement des Aste- ries, in Fauna littoralis Norvegiffi, Seconde Livraison, 1856, PI. VIII.
a. Anal opening. d. Circular water canal.
b. Intestinal canal. e. Madreporic canal.
c. Extremity of the intestinal canal.
49. Young embryo.
50. Young embryo which has assumed a ]ientagonal outline.
51. A young Starfish seen from the actinal side ; b, ambulacral plates ; c, tentacles.
Figs. 49, 50 are much younger than the stages figured by Sars ; see this Plate, figs. 20-23. Fig. 51 is about in the stage of fig. 22.
22
EMBRYOLOGICAL MOXOGEAPHS.
PLATE VII.
Dsvelopment of Asteroidea, continued. Figures from Alexander Agassiz.
a. Anus.
h. Dorsal or wnter pore, inadrcporic opening.
c. Alimentary canal.
d. Digestive cavity.
f'. Median anal arms of Bracliiolaria.
c". Dorsal anal arms of Brachiolaria.
c'". Ventral anal arms of Brachiolaria.
c"". Dorsal oral arms of Brachiolaria.
c'. Ventral oval arms of Brachiolaria.
c^. Odd terminal oral arm of Biachiolaria.
/. Brachiolar arms.
f. Branch of water-tube {lo u-') leading into/.
f. Odd brachiolar arm.
f".
Surface warts at the base of the odd brachiolar
arm (/"). Mouth.
Pistol-shaped oral pouch of oesophagus. Anal pouch of oesophagus. Q?sopliagus.
Vibratile cord, anal part. Vibratile cord, oral part. Water-tube, developing the abactinal area. Water-tube of Brachiolai'ia leading to madre-
poric opening (J), and developing the actinal
area. wv}l. Portion of the water-tube of Brachiolaria
formed by tlie junction of iv and v)'.
m.
m',
V'.
V).
vii
2S. Asfi'rnc'inthion bcryUnun. From Alexander Agassiz, Embryology of the Starfish, 1864 (.Advance Part of Agass. Cont. Nat. Hist. U. S., V.), Pis. I., II. Memoirs Mus. Comp. Zool., V., No. 1, North American Starfishes, 1877, Pis. I., II.
Figs. 13-18. Scyphistoma stages. Figs. 26-30. Brachina stages.
Figs. 19-25. Tornaria stages. Figs. 31-34. Brachiolaria stages.
A mature egg, surrounded by spermatic particles, soon after artificial fecundation. The egg lias assumed a spherical shape, and contains the germinative vesicle and dot. There is no trace of any interval between the yolk anil outer envelope.
The germinative vesicle has disappeared, but the nucleolus remains.
The germinative dot is no longer visible ; the yolk has contracted, and is separated by a slight space from the outer envelope. The egg at this early stage has all the appearance of having already gone through its seg- mentation, the whole yolk being made up of small spherical cells resembling very minute spheres of seg- mentation, although the segmentation has not yet commenced. Two hours after fecundation.
Shows the first trace of segmentation, consisting in a slight depression on one side of the yolk.
The yolk has become flattened on opposite poles ; the " Richtungsbliischen " are visible on one side of the yolk.
Shows the yolk divided into united ellipsoids : the whole yolk rotates slowly, always in one direction, from right to left. The " Richtungsblaschen " are at one pole of the axis of segmentation.
The two segments of the yolk have entirely separated. The " Kichtungsblascheu " are likewise i.solated at one pole of the axis of .segmentation.
The yolk segments are about to separate into four.
The yolk, about to divide into eight spheres.
The yolk is divided into sixteen spheres.
The s]ih(^res of the yolk have undergone two additional subdivisions since the preceding stage.
The segmentation has been carried on still further ; the spheres of segmentation have bec(une somewhat po- lygonal, and form an embryo with a spherical shell consisting of comparatively large cells.
An embryo after its escape from the egg; the wall is no longer of the same thickness throughout, but has liiMome very nuicli thickeneil at one pole (<(), and the spheres of segmentation have become somewhat in- distinct.
Tlie thickened wall of the flattened pole (n) has formed a slight invagination.
The invagination (a) has increa.sed in depth, the .spheres of segnumtation have entirely disappeared, the invagi- nation (re) assumes somewhat the aspect of a rudimentary digestive cavity. Twelve houis after fecundation.
MEM. M. C. Z., IX. No. 2.— ECHINODEEMATA. 23
16. Twenty-two hours after fecundation ; the embryo has become greatly lengthened, and is cylindrical. The cavity (d) has slightly expanded at the closed extremity, and the walls of the embryo are somewhat reduced in thick- ness except at the perforated region ; the body is .'Somewhat translucent, slightly tinged with ochre-color. The opening («) still serves as a mouth, although in more advanced stages a second opening is formed which becomes the true mouth of the enibrj'o, at which time the present muulh then becomea the anus.
ir. Slightly older embryo than lig. 16, seen from the side ; the digestive cavity (</) is no longer in the axis, but is bent to one side (the lower side).
18. Older embryo, seen in profile ; the pouch formed at the end of the closed extremity of the bent digestive cav-
ity (d) is nearer the lower side than in fig. 17, and is moving towards the slight depression (»i, the future mouth) placed in the middle of the larva.
19. A larva somewhat more advanced, seen in prolUe, in which the terminal ponch of tlic digestive cavity has
actually come into contact with the wall of the lower side at m. The dorsal region of llic jicrforatcd extremity projects slightly beyond the depression in which m is placed. The digestive cavity is not yet divided into distinct regions.
20. A larva somewhat more advanced (end of the second day), seen in profile. The digestive cavity is no longer a
simple bent tube, as in fig. 18 ; it is strongly contracted near the extremities ; at the distal extremity two diverticula have formed, projecting upwards («') ; a second opening (m ) has been formed at the point of con- tact of the former closed extremity of the digestive cavity with the lower side; this connects the (esoph- agus, by a short tube, with the main pouch of the digestive cavity. This second formed opening {iii) is the true larval month, while the first formed opening (a) now becomes the anus, after having, up to this stage, performed the functions of both mouth and anus.
21. Isolated digestive cavity seen from below, showing the position of the mouth and anus on the same side of the
larva. The aual extremity of tlie larva bending over as in fig. 24 at about this stage, thus bringing the anal opening fi'om the extremity of the larva to the lower side. The two diverticula («-• w') of the digestive cavity (the future water-tubes) are so far differentiated as to be quite distinct from the digestive cavity. The walls of these diverticula are excessively attenuated, and are scarcely connected with the digestive cavity.
22. Larva somewhat older than stage of fig. 21, seen from above, in which the two small bodies, ir, «', the diverti-
cula of younger stages formed from the pouch of the digestive cavity at its closed extremity (the problem- atic bodies of Miillcr), have entirely separated from the digestive cavity from wdiich they weie formed ; the three divisions of the original cavity into intestine, stomach, and resophagus are plainly markeil out.
23. Older larva, seen from below at the end of the third day after fecundation, showing the triangular shape of
the mouth (m), the greater size of the problematic bodies w, w' (the water-tubes), wliieh increase inde- pendently and at an unequal rate ; the tube tc' communicates with the madreporic opening (?)) ; it also shows the position of the rudimentary oral and anal vibratile crescent cords.
24. The same as fig. 23, seen in profile, to show the position of the mouth in a strongly marked depression, the
gieat increase in size of the oral part of the oesophagus, the swelling of the stomach, and the bending of the extremity of the intestine back and downward toward the mouth, so as to make a small angle with the trend of the stomach.
25. Slightly older larva, seen from above. The principal difference between this st.age and the preceding one con-
sists iu the greater increase in size of the vibratile crescents, which now form two small plastrons, and the greater size of the water-tubes. The intestine also bends so as to make, when seen in profile, almost a right angle with the stomach, which is piished out farther toward the anal extremity.
26. More advanced larva, seen from the left profile, in which the oral pouch has assumed its characteristic pistol-
shape. The stomach and intestine make a sharp angle with each other, the latter being much longer than the stomach proper. In its present aspect it closely resembles a retort, the stomach being the receiver, the intestine the tube. The anal and oral vibratile crescents are greatly extended towards the extremity of the body, the one on the oral, the other on the dorsal side.
27. A larva six days after fecundation, seen from the right profile ; the water-tubes extend beyond the opening of
the mouth, the tube leading from the dorsal water-pore (madreporic body) to the water-tube (»■') is quite distinctly seen.
28. The same larva as fig. 27, seen from below, showing the intestine thrown to one side of the axis of the larva,
the water-tubes extending along the sides of the stomach toward the anal extremity.
29-34. Asteracantkion prdlidus. From Alexander Agassiz, Embryology of the Starfish, 1864 (Agass. Cont. Nat. Hist. U. S., v.). Pis, III., IV., VII. Memoirs Mus. Comp. Zool., 1877, V., No. 1, North American Star- fishes, Pis. III., IV., VII.
29. Larva seen from the right profile, somewhat more advanced than any larva of A. bcryiimm raised by artificial
fecundation.
30. The same larva seen from the oral side. The water-tubes have greatly increased in diameter ; they have
united beyond the mouth, and also extend along the sides of the stomach so as to meet, but without unit-
24 EMIiRYOLOGlCAL MONOGRAPHS.
iiig. The slight lobes along the course of the vibratile conl iudicate plainly the position of the median arms {<;'). of the dorsal anal (<;"), the ventral anal {<:'"), and the dorsal oral arms {c'"'). The greatest thick- ening of the vibratile cord is found at the rudimentary median arms. Beyond the mouth is shown the gi-eat development whiidi the oral portion of the water-tube has taken. This and the preceding figure also show the mode of formation of the oral pair of ventral arms (t^), as well as the first sign of the odd brachiolar appendage (/')• 31. Older larva, seen from the mouth side. Thus far the arms hare altered but little the character of the outline of the larva. In this figure, however, some of them are sufficiently developed to be capable of considerable motion. The median arms (c') especially are far in advance of the others. The anal arms all develop so as to become more slender at first, and a.ssume their true character earlier than the oral arms, which during the early stages are always more lobe-like, and take their final shape later than the anal arms. At the angle where the oral ventral arms and the odd ami come together, at the base of the oral arms, slight swell- ings are formed (/), which are the first indication of the pair of brachiolar arms (//") ; the odd brachiolar arm (/') can only be seen in a profile view (see figs. 29, .32, 33), though in this figure it can be traced as a double outline of the odd ami o^ (/'')• ^^'^ <^'^" already see a constriction of the water-tube as it passes into the odd arm, and from tliis (nearer the mouth) are sent off two small pouches (/'./'), (see also figs. 32, 33,) which enter into the brachiolar pair of arms (/). The fii'st trace of the actinal area of the future Star- fish is also plainly visible (') on the water-tube [w') on the left side of this figure.
32. Fig. 31 seen in profile.
33. An adult larva seen from the right actinal profile ; the arms are in the position which they take when the
larva is moving rapidly, arched towards the median arms, the brachiolarian arms alone being curved in the opposite direction from the others. In this figure the crescent-shaped amhulacral pentagon, as well as the lobed pentagonal outline of the abactinal area, is plainly seen.
34. A greatly magnilied figure of a full-grown Braehiolaria, at rest, in its natural attitude, with the Starfish almost
ready to resorb the larva ; the obliquity of the planes in which the actinal and abactinal pentagons are situated is especially well seen in the pointed anal extremity of this Braehiolaria. No letters have been added to this figure, as the different parts can be readily distinguished by comparing it with figs. 31-33.
MEM. M. C. Z., IX. No. 2. — ECHINODERMATA.
25
PLATE VIII.
Development of Asteroidea, continued.
Figures from Alexander Agassiz, Johannes Muller, and S. Lov^N.
a. b. c. d. d'.
1. V. IK m.
V-- 1^ .
2> c.
Anus.
Dorsal or water pore, madreporic opening.
Alimentary canal.
Digestive cavity.
Abactinnl water-tubss in the angle of the rays of the young Starfish.
Eye of Starfish at the base of the odd tenta- cle {/').
Dorsocentral plate.
Interradial plate.
bi-achial terminal plate.
Mouth.
Opening for passage of arabulacral sucker.
(Esophagus.
Spines on edge of ray of young Starfish.
Spines of exterior rows along the abactinal surface of the rays.
Spines of middle row, on the abactinal .surf;ice of the rays.
Central spine of the abactinal surface of the young Starfish, with centrodorsal plate (/). . Different forms of pedieellarise.
Plate at the junction of adjacent rays (ovarian plate).
Abactinal surface.
?•'. First set of five limestone y rods which appear on the abactinal surface, and eventually be- come the terminal brachial plates (P).
r". Second set of five y rods to appear on the abactinal surface, ami which eventually be- come tile iiitenadial plates (/').
»-'-c5. The first to fifth arm-lobes of the young Star- fish, »•! being the j-ay nearest the madre- poric opening.
s. Actinal surface.
1 1 t. Tentacles or water-system lobes of the young Starfish.
t'. Odd terminal tentacle.
t". Ambulacral tube.
O-l^. First to fifth lobes of the water system, corre- sponding to the first to fifth ami -lobes of the young Starfish (j-'-?-5).
u. Lateral amliulacral plates, surmounted by spines.
u'. Median ambulacral plates, carrying very small spines.
w. Water-tube upon which the abactinal area de- velops.
w'. Water-tube communicating with the madre- poric opening, upon which the actinal area is developed.
1-23. Astcracanthion pallidus, continued. From Alexander Agassiz, Embryology of the Starfish, 1864 (Agass. Cont. Nat. Hist. U. S., V.), Pis. V., VI., VII., VIII. Mem. Mus. C'onip. Zooh, Vol. V., No. 1, North American Starfishe.s, 1877, Pis. V., VI., VII., VIII.
As the figs. 1-7 are intended to illustrate the development of the Starfish proper, the anal part alone of the Brachiolaria is represented ; figs. 2-4 correspond to a Brachiolaria which has reached a stage about as ad- vanced as that of PI. VII. fig. 31 ; figs. 5-7 are stages of development of the young Starfish vvliich are only found on fully grown Brachiolaria, and in wliich, excepting these changes of the Starfish itself, but slight modifications take place. 1 , 2, 6. Represent that profile of the anal part of the Brachiolaria, in successively more advanced stages, which shows the water-tube upon which is developed the actinal area.
3. Represents the opposite profile of the anal extremity of the Brachiolaria, showing the water-tnbe upon which is
developed the abactinal area.
4. 7. Represent the ventral side of the anal extremity of the Bracliiolaria, showing the extremities of the actinal
and abactinal areas of the .Starfish.
5. Represents the dorsal side of the anal extremity of tlie Brachiolaria, showing the opposite extremities of the
actinal and abactinal areas of the Starfish. Owing to the transparency of the Brachiolaiia, either the actinal or the abactinal area is always projected upon the other, when the larva is seen in profile. In the dorsal or ventral views, the angle made by the actinal and abactinal areas becomes visible.
26 EMBEYOLOGICAL MONOGRAPHS.
1. Actiiial profile of the anal part of the water -tube (u'') of the Brachiolaria, previous to the appearance of the
pentagon of lobes. In stage of PI. VII. fig. 27.
2. Soniewliat more advanced actiual profile, showing the anibulacral pentagon, as well as the position of the ten
limestone rods r'-r' and r"-r" (the terminal and interradial plates), which are seen through the thickness of the larva on the surface of the other water-tube («■). In a stage iutermediate between those of PI. VII. figs. 30 and 31.
3. A larva in the same stage as the preceding figure, seen from the opposite profile, to show the abactinal area.
4. The same larva seen from the ventral side of the Brachiolaria, to show the relative position of the pentagons of
the two areas ; only two of tlie rods of the abactinal side are seen, while the edges of three of the actiual folds (l) can be perceived, one above the other, on the footlike projection formed by the fohliug of the water-tube ic'.
5. A dorsal view of the Brachiolaria, showing a well-advanced embryo ; the arm-lobes have become indented, the
arms themselves are separated by a deep cut, the y rods have extended so as to form almost a continuous network over the whole abactinal area. The actinal pentagon has assumed the shape of prominent loops projecting beyond the footlike oblique fold of the water-tube.
6. The same embryo seen from the actinal profile ; the inner tentacular folds have become tipyied with a trian-
gular point. The thickness of the abactinal surface prevents the network of cells on the edge of the arms from being seen.
7. The same, from the ventral side of the Brachiolaria. This figure shows, perhaps better than any other, the
relative position of the extremity of the two yientagonal warped surfaces. The rough outline of the Starfish is due to the manner in which the tubercles of the abactinal surface project aliove it. The Starfish in this condition is at the point of resorbing the larva. The manner in which this resorption takes place is shown on tig. 23 of this Plate.
8. Quite an advanced embryo Starfish, in which all traces of the appendages of the Brachiolaria have entirely
disappeared. Each side of the pentagon of suckers is a rosette made up of seven loops ; the limestone par- ticles are deposited so as to project at the angle of the arms between the tentacular loops. The mouth is movable, the pentagon is not closed, and the Starfish is not yet symmetrical ; the shape of the different rays is not identical.
9. Magnified view of one of the anibulacral tubes of the ])receding figure, with its rudimentary tentacles.
10. The young Starfish in which the two pentagons have almost closed, and been brought into jiarallel planes.
Tliere has been a great im-rease iu the size of the cut between adjoining rays ; the spines also have grown longer and more pointed ; the limestone points of tlie angle of the the rays have advanced nearer the cen- tre. The Starfish is not ipiite symmetrical, nor are all the arras exactly alike.
11. The same young Starfish, from the actinal side, showing the great increase in size of the anibulacral system.
The tentacles are now long pouches on each side of the main tube. The basal tentacles of one of the arms are much farther apart than all the othei-s, and this is the last indication that the ambulacral pentagon is not closed.
12. An abactinal view of one ray, and of the centre of a young Stai-fish, in which the spines project far beyond
the edge of the disk. The arm-plates and the interradial plates have liccinnc connected by a narrow bridge. The original limestone rods are so much thickened by additional deposits that they form elliptical cells, which have entirely lost the polygonal character of the younger stages.
13. One arm and portion of the centre of the most advanced of the young Starfishes which have been raised from
the Brachiolaria', from the actinal side. The three pairs of tentircles have suckers ; the deposit of limestone of the actinal area has a cellular structure. In this stage the madreporic body is still placed on the lower side, on the very edge of the disk. There is a prominent eye-spot at the base of the odd tciininal tentacle. The young Starfish represented iu figs. 13 and 14 is about four months old.
1-1. The same young Starfish as fig. 13, seen from the abactinal side ; the spines are very prominent, long, some- what spreading, becoming sometimes even fau-shaped at the extremity. The limestone cells are gradually assuming the character of those of the adult, small cells within larger ones ; the cut between the rays is very deep.
l.'i. Till' same young Starfish, seen in profile, to show the great development of the abactinal area, and the Echi- nus-like arrangement of the spines in the young St.irfish. The odd tentacle, with the eye at its base, is seen turned up between two of the spines.
16. Two rays and the centre of a young Starfish, about in the stage of fig. 12, seen from the actinal side, in which
the ambulacral tube is concealed by the limestone deposit ; the pair of terniiual tentacles has as yet increased but little in sizK in comparison with the other pairs, which have become so long that they extend beyond the edges of the arms. The eye, a brilliant carmine spot, makes its ajipearance at about this stage. The mouth is a well-defined pentagonal opening, limited by the actinal limestone depo.sit.
17. One of the rays and centre of a young Asteracanthion, about one year old, seen from the abactinal side.
18. Actinal view of an arm of a young Asteracanthion, probably in its third year.
19. 20, 21. Magnified views of spines (;)), and of rudimentary pediccllaria; (/>', }•").
MEM. M. C. Z., IX. No. 2.— ECHINODERMATA. 27
22. Odd terminal tentacle, with tlie eye-speck (f) of a young Asteracanthion about in the stage of fig. 18.
23. Shows the process of resorption of the Brachiolaria into the young Starfish ; it coniniences at the anal extrem-
ity, and in this case has gone on sufficiently far to leave the young Starfish riding upon the oral extremity of the Brachiolaria, which alone, with its hrachiolarian and terminal arms, has retained its original shape and proportion.
24. Bipiimaria asteriijrra. From .Johannes Miiller, Ueber die Larven und die Metamorphose der Echinodermen,
Zweite Abhandlung, (1S48,) PI. II. Abhandl. d. K. Akad. der Wiss. Berlin, 1849.
24. A Bipinnaria, 1" in size, seen from the ventral side : 1, upper arm (anal) ; 7, ventral arm (oral) ; S, 3, 4, 5, G,
dorsal arms ; a, mouth ; h, anus ; d, dorsal vibratile coid ; il', ventral vibratile cord ; c, a', furrow between the vibratile cords of the arms.
25-28. Asterias gladalis. From S. Loven, Etudes sur les Echinoidees, 1874, PI. LIIl. Kongl. Svenska Vetens.
Akad. Handl., XL, No. 7.
25. Young Asterias, 1.3 mm., seen from the ventral side ; a, i, ambulacral plates.
26. The same, seen from the abactiniil side. In this stage the skeleton is almost exclusively made up of the api-
cal and of the ambulacral system : a, dorsocentral plate (basal) ; h, interradial plates (genital) ; c, the terminal [dates (ocular). The small |)lates ( ;)) lietween the terminal and the angle of the interradial plates are the first dorsal arm-plates.
27. Older specimen, 2 mm., seen from the abactinal side ; the single plate (;;) of the preceding figure is replaced
by a set of three plates. Lettering as before.
28. Another individual, 4.5 ram., seen from the dorsal side ; one of the genital plates has been pierced by the
madreporite (r) ; in epch ray a jiair of dorsal water-tubes {t r) have made their appearance. Lettering as for fig. 26.
28 EMBRYOLOGICAL MOXOCUAPHS.
PLATE IX.
Development of the Echinoidea. Figures from Emil Selenka, Wilhelm Busch, Johannes MiJLLER, J. W. Fewkes, H. Garman and B. P. Colton, and Alexander Agassiz.
1-16. Echinus miUaris. From E. Selenka, Keimbliittcr iiml Organ.inlage der Echiniden, 1880, PI. V. Zeits. f.
Wiss. Zool., XXXIII.
1. Free swimmiii" Til.istula, optical section ; o, position of the fiituve anus ; b, funnel-shaped depression ; /, seg-
mental cavity. 16 hours after artificial fecundation.
2. Blastula with the two clusters of mesodernr cells, tn, m', which have separated from the thickened part of the
ectoderm ; a, position of the future anus. 18 hours.
3. Commencement of the invagination. 22 hours.
4. Young gastrula, optical section; a, gastrula mouth (later anus). 27 hours.
5. Gastrula, optical section ; small limestone rods have made their appearance : m, digestive cavity ; m, m', accu-
mulation of cells from which the y-shaped rods take their origin ; c, expansion of the closed e.vtremity of the dio-estive cavity, from which are developed the diverticula forming the water-tubes. 43 hours.
6. Gastrula, dark mesoderm cells at the upper extremity of the larva; the diverticulum (water-system) of the
din-cstive cavity forms a T across its closed extremity ; the limestone rods have greatly increased in length and are surrounded by the nomadic skeleton cells. 48 hours.
7. Gastrula, after iJ4 hours. Optical section, .showing the position of the limestone rods. The digestive cavity,
B, is becoming differentiated into an esophagus, stomach, and intestine. The water-system, v ji, has com- pletely separated from the digestive cavity. Lettering as before.
8. 9 10, 11, 12. Successive stages of the digestive cavity and its diverticulum, showing the manner in which the
water-system is formed as a diverticulum at the blind extremity of the digestive cavity, and how it becomes separated from it. This process takes place, according to Selenka, in less than three quarters of an hour.
13. Pluteus, after 60 hours. It has lost its cylindrical outline, the rudiments of the arms appear, and the oral and
anal planes of the larva are developing in opposite directions.
14. Diagram of the same Plnteus as fig. 13, seen in profile ; a, oesophagus ; ^, stomach ; y, intestine. The skele-
ton is not indicated. 1.1. Pluteus 94 hours after fecundation : o, mouth ; a, anus (gastrula mouth) ; o, oesophagus ; ft stomach ; 7, in- testine ; vp, right water-tube; p, left water-tube, which subsecjuently becomes the water system of the young Echinus and tlie left peritoneal sac. Tlie lesopliagus, a, is capable of a considerable contraction and expansion ; the narrow passages h and i, leading from the resophagus and intestine into the stomach, are well seen in the profile figure of the same Pluteus (tig. 16).
16. The same Pluteus as fig. 15, seeu in profile. The cilia which still cover the whole Pluteus are not represented
in this figure, nor in figs. 13, 14.
17-19. StrongylocaifrolHS Hvitlii.i. From E. Selenka, Keimblatter und Organanlage der Echiniden, 1880, I'l. Vll.
Zeits. f. Wiss. Zool., XXXIII.
17. Blastnla m.aking its escape fiom the egg ; d, outer membrane.
18. The same blastnla, free, optical section ; e a, thickened wall of the blastula at the pole where the invagination
will take place.
19. Gastrula 43 hours old. The va.soperitoneal vesicle has separated from the digestive cavity. Optical section,
the two first j/-shaped limestone rods of the skeleton have appeared.
20-23. Arhacia puslulosa. From E. Selenka, Keimblatter und Organanlage der Echiniden, 1880, PI. VII.
Zeits. f. Wiss. Zool., XXXIII.
20. Blastula 30 liours after artificial fecundation ; c n, thickeued wall of the blastula, where the invagination will
tiike place ; /, segmental cavity ; </, anal pole.
MEM. M. C. Z., IX. No. 2. — ECHINODEEMATA. 29
21. Gastnila, optical section ; u, digestive cavity. 48 hours.
22. Gastnila, 68 hours old.
23. Embryo 72 hours old ; the vasofieritoneal vesicle has sep.arated from the digestive cavity.
24-27. EchinocarcUam cordatum. From E. Selenlca, Keiniblatter uud Organanlage der Echinideii, ISSO, PI. A' 1 1.
Zcits, f. Wiss. Zool., XXXI II.
24. Blastula, 30 hours ; a, position of the futui'e auus ; /, segmental oavity ; g, funnel-shaped <lepression in the
ectodermal cells at the anal pole. 24'. Blastula showing the commencement of the invagination ; /«, 'nil, clusters of cells of the mesoderm which have become separated from the ectoderm at the anal pole.
25. Gastrula 40 hours hold.
26. Longitudinal optical section of the same.
27. Young larva 50 hours old, optical section ; the vasoperitoneal sac has become separated from the digestive
cavity ; this is now differentiated into the a, cesophagus ; /3, stomaidi ; and y, the intestine.
Figs. 1-27 are grouped together to show, in the earlier stages of the Pluteus of several Echini types, the forma- tion of the mesoderm cells, the invaginations of the gastrula, the development of the vasoperitoneal sacs, and the differentiation of the original digestive cavity of the gastrula. See also PI. X. figs. 14-33.
Figs. 28-45 are devoted mainly to showing the formation of the arms of the Pluteus and the develojiment of the young Arbacia. See also PI. X. figs. 32-44.
28-37. Arbacia j>usliilosa.
28. 29. Arbacia pustulosa. From W. Busch, Beobachtungen iiber Anatomic und Entwickelung einiger Wirbel-
losen vSeethiere, 1851, PI. XIII.
28. Young Pluteus, seen from the mouth side ; the oral extremity does not yet pi'oject beyond the level of the fold
connecting the dorsal anal arms.
29. Somewhat more advanced than the preceding stage, seen from the dorsal side ; the oral extremity projects
nearly as much as the dorsal arms.
30-37. Arbacia piiatn-lomi. From .Tohannes Miillei-, Ueber die Gattungen der Seeigellarven, Siebente Abhandlunf,', (18.13,) I'ls. II., III., IV. Abhandl. der K. Akad. der Wiss. Berlin, 1855.
a. Anus. o. rEsophagus.
d. Digestive cavity (stomach). t. Tentacular lobes of water-system.
om. Mouth.
30. Young Pluteus seen from the ventral side ; somewhat older than the oldest stage copied fi'om Busch (fig. 29).
31. The same as fig. 30, seen in profile.
32. Still older Pluteus, seen from the ventriil (mouth) side ; the oral arms, mere knobs in the preceding stages (figs.
30, 31), have greatly increased in length ; first trace of the posterior anal pair of arms.
33. Still older Pluteus, seen from the dorsal side. The posterior pair of anal arms pi-ojects well beyond the general
outline of the anal extremity ; the auricles are beginning to form as folds of the vibratile cord, between the dorsal and oral arms, and the second pair of oral arms is present as mere knobs at the base of the oral arms.
34. Still older Pluteus, seen from the mouth side ; the daik ]iigment-spots of the abactinal region of the young Ar-
bacia are seen through the Pluteus membranes of tlie anal extremity ; the jiosterior pair of anal dorsal arms has grown rapidly since the last stage (fig. 33), exceeding in length the oral arms ; the second pair of dorsal arms is also present, equalling in length the oral arms ; the auricles are also well developed.
35. Fully developed Pluteus, with two pairs of oral arms and a smaller pair of dorsal oral arms, with large auricular
arms, and the long median dorsal arms of equal length ; the tentacular lobes of the water system, t, are well developed, and pedicellaria; even have made their appearance on the surface of the young Arbacia. In this stage the young Arbacia is about to resorb the Pluteus.
36. 37. Young stages of Arbacia ; 36 seen from above, 37 somewhat in profile. The club-shiipeil spines are the
young spines of the edge of the test of the young Arbacia ; the straight spines are the remnants of the Pluteus rods in process of atrophy and resorption. In the stage 37, young pedicellariae are seen.
38-45. Arbacia punctulata.
38-40. Arbacia piwctulata. From J. W. Fewkes, On the Development of the Pluteus of Arbacia, 1881, PI. I. Memoirs Peabody Academy of Science, Sixth Memoir.
38-40. Young Plutei, showing the develojiment of the calcareous rods : ?», mouth ; d, digestive cavity. Some- what younger than the stages of Arbacia figured by Busch (figs. 28, 29), and somewhat older than those given by Selenka (figs. 22, 23).
30 EMBRYOLOGICAL MONOGItAPIIS.
41. Arbacia punctxdata. From Alexander Agassiz, Revision of the Echini, Part IV., 1874, p. 729, fig. 6ij.
lUust. Cat. Mus. Conip. Zool., No. VII., Pt. IV.
41. Adult Pluteu.s of Arbacia pimctulata; m, mouth. The dark spots of the anal extremity are the pigment spots
of the young Arbacia.
42-43. Arbacia jmnclulata. From H. Garman and B. P. Colton, Some Notes on the Development of Arbacia puuctulata. Lam., 1882. Johns Hopkins University, Baltimore, Studies from the Biological Laboratory, II., No. 2, PI. XVIll.
42. Young Arbacia wliicli lias begun the resorption of the Pluteus ; the oral part of the Pluteus is greatly
.shrunken (o /).
43. The process of resorption is more advanced, only a trace of the oral ])art of the Pluteus is left (o /), and the
limestone rods of tlie anal arms a[>pcar like tall spines on the abactiual side of the yonng Arbacia. The odd tentacular suckers are very prominent.
44. 45. Arbacia punctii/ala. From Alexander Agassiz, Revision of the Echini, Pt. IV., 1874, p. 734, figs. 68, 69.
Illust. Cat. Mus. Comp. Zobl., No. VII. Pt. IV.
44. Yonng Arbacia punctidata, 1.5 mm. in diameter, including the spines, seen from the abactiual side, showing the
anal sj'stein with its four plates. The apical system covers nearly the whole abactinal area, and is covered by embryonic sessile tubercles : a few pedicellariie have made their appearance. The edge of the test carries huge flattened spines triangular in section, nearly equalling in length the diameter of the test. The amtu- lacral suckers are slender, .some of them longer than the diameter of the test, and provided with somewhat pointed sucking disks. The whole test and the spines ai-e thickly covered with dark violet pigment .spots and patches.
45. The same as fig. 44, .seen from the actinal side, showing the connected limestone deposit of tlie actinal sur-
face covering tlie aniliulacral tubes ; the longest tentacles are those nearest the odd terminal tentacle ; the odd tentacle is a small, short, slender tube without a sucking disk.
MEM. M. C. Z., IX. No. 2.— ECHINODERMATA.
31
PLATE X.
Development of the Echinoidea, continued. Figures from Alexander Agassiz.
a. b. c. d.
c', e
/■ k. m. ms.
0.
Anus.
Madreporic body. Alimentary canal (intestine). Digestive cavity (stomach). ', e'", civ. Arms of the Pluteus. Brachiolar arms ? Teeth of young Echinus. Mouth.
Mesoderm cells.
Interambulacral tubercles of young Echinus. Ambulacral tubercles of young Echinus. (Esophagus. Pedicellaris. First y rod of the Pluteus.
Pigment spots of the long Pluteus arms.
Interambulacral spines of young Echinus.
Young spines of embryo Echinus.
Tentacles.
Odd terminal tentacle. f^, fi. First and second pairs of lateral ambulacral tentacles.
Anal part of vibratile cord.
Oral part of vibratile cord.
Vibratile epaulettes.
Water-tube.
Water-tube communicating with the madre- poric body.
s'.
s".
s'".
(.
t'.
V. V'.
v". w. w'.
1-17. StrongylocaUrotvs Vrobachiensis. From Alexander Agassiz, Revision of the Echini, Pt. IV., 1874.
Cat. Mus. Oomp. Zool., No. VII., pp. 709, 710.
Illust.
18-44. Slrongylocentrntus Drolachknsis, continui^d. From Alexander Agassiz, On the Embryology of Echino- derms. Mem. Am. Acail., IX., 1864, selection from figs. 1-25.
1. Mature egg.
2. Egg in which the germinative vesicle has disappeared after fecundation.
3. The germinative dot has also disappeared. The yolk has separated from the outer membrane, leaving an
interval between it and the envelope.
4. The yolk has become depressed at one pole.
5. The same depression takes place at the two poles. 6-12. Different stages of segmentation.
6. The first trace of segmentation is a slit at one pole.
7. The yolk is divided into two large ellipsoidal masses.
8. The masses subdivided again.
9. The four .spheres show a tendency to a further subdivision.
10. There are now eight spheres of segmentation.
11. There are thirty-two spheres, and they already show a tendency to form an envelope.
12. There are sixty-four spheres, and the walls of the embryo are already indicated.
13. The segmentation has gone on until the spheres are quite small, and the wall of the embryo very distinct.
14. The embryo has just escaped from the egg ; the wall is thickened at one pole.
15. A slight invagination forms at the thickened pole.
16. The invagination has become somewhat deeper.
17. Oilier embryo more elongated, with thin walls at the upper extremity; the invagination now performs the
function of a rudimentary digestive cavity.
18. Still older embryo, seen in profile ; the digestive cavity is no longer in the axis of the Pluteus.
19. The same as fig. 18, seen from above.
20. Profile view of a Pluteus, somewhat more advanced than fig. 18 ; the digestive cavity is bent towards the ven-
tral side of the larva.
21. Somewhat older Pluteus, at the end of the fourth day, seen from above. At the closed extremity of the
digestive cavity two small diverticula have formed (w, w^), the first appearance of the water-tubes.
32 EMBEYOLOGICAL MONOGIIAPHS.
The digestive cavity itself shows the fust trace of dilfcreiitiation iuto intestine, stomach, and oesoph- agus.
2"2. Prolile view of an embryo, somewhat older than fig. "21, at the beginning of tlie fifth day ; the intestine, c, stomach, d, and cesophagus, are well separated ; the anal vibratile cord (c") bulges out considerably beyond the depression in the vi.-ntral side of the Pluteus.
23. Embryo at the end of the fifth day, seen from the mouth siiie ; the water-tubes (ii>, w') are only slightl)' con- nected with the digestive cavity ; they also show a difference in size. The original limestone rod has given off a shoot, the rod of a new arm to be developed at v.
2-t. Fig. 23 seen from the anal extremity, to show the great change of form which has taken place from the early cylindrical shape of the embryo.
25. A profile view of lig. 23. The embryo has become pear-shaped, the cesoph.agus has bent over to reach the
ventral side ; the anal opening is also somewhat ventrally placed ; the depression at m, where the new montli is to be formed, is in contact with the ossophagus ; the anal and oral vibratile cords have increased in prominence.
26. A profile view of an enjbryo, taken at the beginning of the seventh day. The mouth, m, is open ; the water-
tube !(;' reaches nearly to the dorsal surface. The currents, which previous to this stage had carried the food through the only opening, a, into the digestive cavity as far as o, and then were reversed to eject the digested matter, now come in through the mouth, m, pass through the a-sophagus, o, rotate about in the stomach, rf, and pass out through the first-formed opening, the anus, a, which is liereafter only used to eject the food.
27. A Pluteus at the end of the eighth day, seen obliquely from the ventral side, to show the course and shape of
the vibratile cord.
28. Profile view (actinal) of a stage slightly older than that of fig. 27.
29. The same as fig. 28, seen from the ventral .side.
30. Somewhat more advanced Pluteus, to show the changes the vibratile cord has undergone since the stage of
fig. 27 ; seen obliquely from the ventral side.
31. A Pluteus during the tenth day, seen in profile, shows the beginning of the small arms c'" and civ.
32. The same as fig. 31, seen from the mouth side. The arms c' liave been greatly developed ; the differentiation
of the intestine, c, the stomach, d, and the resophagus, is quite complete. First appearance of the vibratile epaulettes, r". The water-tubes have not yet united, and have not greatly increased in size from the jire- ceding stage.
33. Profile of a Pluteus during the twenty-third day. The arm <" has increased greatly in length, and a con-
siderable increase of the vibratile epaulettes is to be noticed.
34. The same as fig. 33, seen from the dorsal side, to show the relation of the rods of the aims c', c", c'", to
each other ; the water-tube Jc' shows the first indication of a large tentacular lobe.
35. Fig. 34, seen somewhat obliquely, in an attitude similar to that of figs. 27 and 30, to show the coimection of
the different parts of the vibratile cord. 3G. A much more advanced Pluteus, fished up from the surface. The rods extending into the arms are made up of three sets of rods united by short transverse bars ; the whole oral extremity of the larval body has greatly lengthened ; the arms c'" and fiv are longer than in the preceding stages, c', c", and c'" being nearly of equal length ; the arras show a tendency to a paired arrangement of e', e", and c'", c'v. Additional ten- tacular lobes liave been formed in the water-tube ^v', and the water-tubes have become united in the oral extrenuty beyond the saclike pouch of the mouth of the Pluteus.
37. Fully developed Platens of SlrOHgijloccntrotu.i, in which the young Sea-urchin has alreaily encroached .some-
what on the anal extremity ; its spines are quite well marked ; the vibratile epaulettes have acquired a gi-eat size ; two very prominent spots, s', s', in the arms <■', c". At the base of the oral extremity of the mouth pouch a rudimentary appendage, /, appears ; this is perhaps the homologue of the brachiolarian appendag<-s of the Brachiolaria of Asteracanthion. The arras c', t", and c'", t-iVj mv. now of nearly equal length, and ananged in pairs.
38. Fig. 37 seen from the oral extremity of the Pluteus.
39. Profile view of fig. 37.
40. A young Echinus, iniTuediately after the resorption of the Pluteus, seen from the abactinal side. The anal
opeiung cannot be traced in the youngest specimens, tlio\igh it is. very apparent in somewhat nmre advanced stages (a, lig. 43).
41. A young Ecliinus, somewhat more advanced tluan the stage of fig. 40, seen from the actinal side ; the tenta-
cles have become more slender ; the odd tentacle V especially, wherk fully extended, more than equals the diameter of the test ; the interambulacral spines of this side are nearly as long as the diameter of the test. The actinal system is not well separated from the coronal test. The two tentacles nearest the actino- stome are remarkable for the great development of the sucking disk.
42. The .same as fig. 41, seen from the abactinal side ; the .spines of the abactinal area are remarkable for their
fan-shaped spiny extremities.
MEM. M. C. Z., IX. No. 2. — ECHINODEEMATA. 33
43. Young StrongyTo-.entrotus, measuring one fifteenth of an inch in diameter, including the siiines ; a number
of long-stemmed pedieellari;e have developed on the abactinal side ; the tentacles have become quite slender, and carry a comparatively large sucking disk ; the spines have lost their embryonic character, and have assumed the general appearance of those of the adult. The anal system is very prominent, a large circular opening covered by a single plate, a, leaving the anal opening on one edge of the anal system.
44. The test of a young Sea-urchin, in the stage of tigs. 41, 42, stripped of its spines, seen from the actinal side ;
the actinal system is comparatively large, and, as in C'idaris, the tubercles are large and few in number ; no miliary tubercules are as yet formed. The teeth are simple, and the accessory parts of the jaws are not developed.
34 EMBRYOLOGICAL MONOGRAPHS.
PLATE XI.
Development of Echinoidea, continued. Figures from Johannes Muller, August Keohn, and
Alexander Agassiz.
Spatangus purpureus.
1 3, 5. From August Krohn, Ueber die Larre von Spatangus inirpureus. Archiv f. Anat. Physiol, u. Wiss.
Med., 185.3, PI. VII.
2 4, 6. From Johannes Miiller, Ueber die Larven und die Metamorphose der Ecliinodermen, Vierte Abhandlung
(1850-51), Pi. VIII. Abhandl. d. K. Akad d. Wiss. Berlin, 1852. 7, 8. From Johannes Miiller, Ueber die Larven und die Metamor[diose der Ophiureu nnd Seeigel (1846), PI. III.
Abhandl. d. K. Akad. d. Wiss. Berlin, 1848.
9. From Johannes Miiller, Ueber die Gattungen der Seeigellarven, Siebente Abhandlung iibcr die Metamorphose
der Echinodermen, 1855, PI. V. Abhandl. d. K. Akail. d. Wiss. Berlin, 1855.
A. First pair of dorsal arms. G. Tliird pair of oral arms.
B. Seeond pair of dorsal arms. ft. Mouth.
c. Pair of anal arms. «'. (Esophagus,
r. Odd anal arm. b. Stomach.
E. Second pair of oral arms. b'. Intestine,
r. First pair of oral arms. o. Anus.
1. Oue of the older Plutei raised by artificial fecundation, with a rudimentary odd anal arm, D, and a single pair
of dorsal arms, a.
2. Older Pluteus, in which the odd an.al arm, D, has greatly increased in size, and the first pair of oral arms, F,
has made its appearance. Seen oblii[uely.
3. Older Pluteus, in which tlie dorsal arms. A, have still further developed. Dorsal view.
4. Older than fig. 3. Tlu- growth of the Pluteus since the last stage has been principally in the elongation of
the oral part of the larva and the lengthening of the odd anal arm. Seen from the mouth side.
5. Pluteus somewhat older than stage of fig. 4. The dorsal arms. A, are nearly twice as long as in the preceding
sta^e, and the rudiments of the second pair of dorsal arms are visible. Ventral view.
6. Older stage, in which the second pair of dorsal arms, B, is nearly as long as the first pair, A ; the rudiments
of the second pair of oral arms, E, have also appeared. Seen from the mouth side.
7. Still older Pluteus ; the first pair of dorsal arms is somewhat longer than the second ; the third pair of oral
arms, g, has been developed, and the anal pair of arm.s, c, has likewise made its appeai-ance. "
8. Older stage, in which the resorption of the Pluteus is well advanced, the anal arms have disappeared, and a
part of the or.al portion of the larva has also been resorbcd by the young Spatangus ; the spines and ambu- lacral s\u'kers of the young Urchin are well seen in the anal part of the Pluteus.
9. Fully developed Pluteus, with all its arms, just before the resorption of the Pluteus begins.
10. Spatangoid Pluteus. From Johannes Muller, Ueber die Gattungen der Seeigellarven, Siebente Abhandlung,
1855, PI. V. Quoted above.
10. This Pluteus may be a younger stage of fig. 9, but, judging from the absence of the pair of anal arms and the
great length of the odd anal arm, it probably does not belong to S. pnrpurcu.f.
11. Echinoid Philrns. From Johannes Miiller, Siebente Abhamlluiig, 1855, PI. V. Quoted above.
11. This remarkable Pluteus differs widely from all known Echinoid larvpe ; it has features in common with the
Brachiolaria, many of its arms being flexible, without rods. These arms are perhaps only such auricles as we find in the Pluteus of Arbacia (see Plate IX. figs. 34, 41). It is probable, therefore, th.at this l.arva will prove to be the Pluteus of a Cidaris or of a Diadema.
MEM. M. C. Z., IX. No. 2. — ECHINODEEMATA. 35
12-18. Echinus lividus. From Johannes Miiller, Vierte Abhandliuig (1850-51), PI. VI., VU. Quoted above.
A. First pair of dorsal arms. b. Stomach.
B. Second pair of dorsal arms. i'. Intestine.
E. Second pair of oral arms. c. Anus.
F. First pair of oral arms. d. Cord of vibratlle cilia. a. Mouth. /. Vibratile epaulettes, a'. Qisopliagus.
12. Pluteus on the sixteenth day after artificial fecundation ; this Pluteus was lemarlcably slow in its development.
13, 14. Pluteus on the eleventh day after artificial fecundation, but more advanced than the preceding stage.
13, seen obliquely from the side ; x is the outline of the depression iu which the inoutli is placed. 14, seen from the mouth side.
15. Somewhat more advanced Pluteus, on the seventeenth day, seen obliquely from the dorsal side, shows the rel-
ative position of the calcareous rods, of the arms, and of the cord of vibratile cilia.
16. Somewhat older Pluteus, in which the arms have greatly lengthened, and there is a slight swelling of the
vibratile cord at the base of the dorsal arms, denoting the position of tlie future vibratile epaulettes.
17. Fully developed Pluteus, with vibratile epaulettes ; the young Echinus is well advanced.
18. Stage in which the young Echinus has resorlied the greater part of the Pluteus ; only a small part of the oral
extremity ami short pieces of the rods of the arms of the larva are left. The rudimentary embryonic spines, X, are quite prominent ; the ambulacral suckers, y, are clearly seen ; one of the longer tentacles projects beyond the disk, and a few pedunculated pedicellarise have made their appearance.
19-27. Echiiwcyamiis pusillu$ ?
19-21. From .Toliannes Miiller, Vierte Abhandlung (1850-51), PI. VIII. Quoted above.
A. First pair of dorsal arms. a'. (Esophagus.
F. First pair of oral arms. I>- Stomach.
a. Mouth. b'- Intestine.
19. Young Pluteus, seen from the ventral side.
20. The same, seen obliquely in profile from the dorsal side.
21. Somewhat older Pluteus, in which the second pair of oral arms is already formed. It is somewhat problemat-
ical if the stages of figs. 19-21 are the younger stages of figs. 22-24.
22-27. From Johannes Midler, Siebeute Abhandlung, 1855, PI. VIII. Quoted above.
a. Mouth. d. Intestine.
b. Qisophagus. e. Anus.
c. Stomach.
22. Young Pluteus, with two dorsal and two oral arms, seen obliquely, looking into the mouth cavity.
23. Somewhat older Pluteus, seen from the dorsal side ; the second pair of oral arms has made its ap|iearance.
24. Fully grown PUiteus ; the young Urchin is not yet far advanced.
25. Pluteus in which the resorption of the anal extremity is well advanced, the young Urchin occupying the whole
of the anal extremity of the Pluteus ; the oral extremity is still nearly unchanged.
26. The young Urchin seen in profile, after the complete resorption and disappearance of the plutean aj)pendages.
J '" iu diameter. The odd tentacles have already well-developed suckers.
27. The same young Urchin as fig. 26, under compression, showing the five teeth, the limestone jilates of the
actinostome, and the single row of embryonic spines placed round the ambitus.
28. Echiimrachnius parmal From Alexander .^gassiz. Revision of the Echini, 1874, Part IV., p. 727, fig. 65.
lllust. Cat. Mus. Comp. Zool., No. VII. Part IV., 1874.
28. Well-advanced Pluteus, remarkable, like the problematic Echinocyarmis Pluteus, fig. 24, for its rounded anal
extremity : a, mouth ; a', oesophagus ; d, digestive cavity ; i, intestine ; a n, anus. Seen from the mouth side.
29. Echinus acutus ? From Johannes Miiller, Ueber die Larven und die Metamorphose .... (1846), PI. V.
Quoted above.
29. Fully developed Pluteus, with rounded anal extremity, large vibratile epaulettes, and comparatively short arms.
Seen from the mouth side. A, first paii- of dorsal arms ; B, second pair of doi-sal arms ; a, mouth ; o', cesoph- agus ; A, digestive cavity ; d, cord of vibratile cilia ; e, calcareous rods of arms ; /, vibi'atile epaulettes.
30. Echinus brevispinosus. From Johannes Miiller, Siebente Abhandlung, 1855, PI. I. Quoted above.
30. Fully developed Pluteus, seen from the dorsal side. This Pluteus is remarkable for the short pair of anal
arms developed at the posterior extremity.
36 EMBKYOLOGICAL MO^'OUKAPHS.
PLATE XII.
Development of Echinoidea, continued. Figures from Alexander Agassiz and C. "Wtville
Thomson.
Young Stages of
1-3. Goniocidaris canaliculata. 17-22. Echinarachnius parma.
4. Dorocidaris jmpillala. 23, 24. Encope emarginata.
5, 6. Astkenosoma hystrix. 26-29. Conolmnpas Sigsbei.
7. Diadema sclosum. 30-35. Hemiaster cavernosas.
^-12. Afellita scx/oris. 36,36'. Spntangus purpurcus.
13-14. McHita tesludinata. 37-40. Brissopsis hjrifera. 15, 16. McIIila Ungifissa.
1-3. Goniocidaris catialicalala. From Alexander .Agassiz, The Zoology of the Voyage of H. M. .S. Challenger, Vol. III. Tart I.X. Reiiort on the Echinoidea, PI. 11., London and Ediub., 1S81.
1. Young specimen, 2 mm. in diameter, seen from the abactinal side.
2. The same as lig. 1, seen from the actinal side.
3. Another young specimen, 3 mm. in diameter, belonging to the long spined type of the species.
4. Dorocidaris papillata. From Alexander Agassiz, Eevision of the Echini, Part II., 1872, PI. II«. 111. Catal.
Mus. Comp. Zool., No. VII. Part II., 1872, PI. 11°.
4. Young specimen, seen from the abactinal side, parti j' denuded. 2.4 mm in diameter.
5, 6. Astlvcnosoma hystrix. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PL 11°.
Quoted above.
5. Part of test of young specimen, measuring 3.1 mm. in diameter, seen from the abactinal side.
6. Part of test of same, seen from the actinal side.
7. Diadema sctosum. From Alexander Agassiz, Revision of the Ei.-hini, Part II., 1872, PI. IP. Quoted above.
7. Young specimen, measuring 2.4 mm. in diameter, seen in profile, showing the anal tnbe projecting between
the spines beyond the level of the abactinal surface.
8-12. Mellila sexforis. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PL XI. Quoted above.
8. Young specimen, 2.4 mm. in diameter, having a Laganum-Iike shape ; the posterior interambulacral lunule is
not as yet to be seen from the abaidinal side.
9. The same from the actinal side, deeply concave, showing the commencement of the posterior interambula-
cral hinule.
10. Young sjiecimen, 4 mm. in diameter, seen from the abactinal side ; first trace of the posterior limule on the
abactinal side.
11. Young specimen, measuring 10.1 mm. in diameter, from the ab.actinal side. The ambulacral lunules all pres-
ent, in different stages of growth.
12. Young specimen, raea.suring 12. 7 ram. in diameter, witli all the ambulacr.il lunules completely pierced
through and well formed.
13-16. Mellita testiidinnta and longifissa. in which the lateral Innnles are formed from notches in the edge of the test. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PL -XL Quoted above.
13, 14. MeVitn tesludinata.
13. Posterior interambulaei-nm of lig. 14, showing the posterior interambnlacral lunule, which in this type is
formed from the lower side, as in ^[. sr.rforis, and forces its way through the test to the abactinal surface.
14. Young specimen ('{), seen from the abactinal side ; the edge of the test shows as yet no trace of the notches
so well developed in fig. l.'i.
MEM. M. C. Z., IX. No. 2. — ECHINODERMATA. 37
15, 16. MuUita kmyijissa. 1'). Young siiccimi'ii, iiiitiiral size, in which the notches forming the ambulacral hinules coniineiiee to close, .seen from the aliaotinal side.
16. Part of test of a young specimen, about J of an incli iu diameter, in wliich the ambulacral lunules hare com-
pletely closed ; seen from the abactinal side. 17-22. Echiiuirachnius parma. From Alexander Agassiz, Eevision of the Echini, Part II., 1872, PL XII.
Quoted above.
17. Young specimen (•^i'^), seen in profile, elongated Echinometra-like stage.
18. The same as fig. 17, seen from the abactinal side ; the anus at this stage opens ahove the ambitus.
19. Somewhat older stage (f ), seen from the abactinal side ; the anal opening is placed nearer the ambitus.
20. Older than the preceding stage (i), seen from the abactinal side; the outline has become somewhat more
elliptical.
21. Older stage, seen from aliove (f ). In the abactinal part of the aml.iuhii la the pores have bocome conjugated.
22. Still older stage, seen from above ( '^~) ; the abactinal part of the ambulacra has become slightly petaloid ;
the anal opening is partly on the ambitus. 23, 24. Encopc emanjinata. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PI. XII.
Quoted ahove.
23. Young specimen in the Moulinsia stage (^i^), showiug the first trace of the posterior interambulacral lunulc
on the actiual -side. 2i. Young Encope, natural size. The posterior interambulacral hinulehas forced its way through from the actinnl to the abactinal surface, and there are traces of the lateral ambulacr.al notches, which are to form the lunules (which may remain closed or open) of the older stages. 26-29. Gonolampas SUjsbei. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PI. XVI.
Quoted above.
26. Young specimen, seen from the abactinal side, partly denuded. 4 mm. in diameter.
27. The same, seen from the actinal side ; the anal opening is on the sloping posterior edge of the ambitus of the test.
28. The same, seen in profile, showing the position of the anal system.
29. Young specimen, in its Echinolampas stage, measuring 12.7 mm. in diameter ; seen in profile.
30-35. Jlemiaslcr cavernosus. From Alexander Agassiz, Report on the Ecliinnidea of the "Challenger," 1881,
PI. XX'. Quoted above.
30. One of the lateral ambulacral petals of a gravid female, showing the mode in which the young embryos are
carried in the deeply sunken petaloid ambulacra. From C. Wyville Thomson, Notice of some Peculiarities in rhe Mode of Propagation of certain Echinoderms of the Southern Sea. Journ. Linn. Soc. Zoology, XIII., 1876, p. 70, fig. 9.
31. Young, 2 mm. in diameter, taken from the pouch of the petaloid ambulacra, still somewhat circular, with
str.aight primary spines, seen from the abactinal side.
32. Somewhat older than the preceding stage, 3 mm. in diameter ; the test carries curved primary spines, seen
from the abactin.al pole.
33. Young, in about the stage of fig. 32, denuiled of spines, showing the simple ambulacral pores, the large anal
opening, within the broad peripetalous fasciole, and the ring of large primary tubercles, forming its inner edge ; about 3 mm. in diameter.
34. The same as fig. 33, somewhat less magnified, seen from the actinal side.
35. Young Hemiaster, measuring 5.5 mm. in diameter ; the anal system is now removed from within the peri-
petalous fasciole to the outer edge of the broad peripetalous fiisciole ; seeii from the abactinal side. 36, 36'. Spatangus purpurens. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PI. XI'.
Quoted above.
36. Young specimen, seen from the abactin.al side (J), showing the straight simple ambulacra of the future
petaloid system of the abactinal part of the test. 36'. Tlie actinostome of the same ; the posterior actinal lip is as yet scarcely developed.
37-40. Bri^sopsin lyrifcra,. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PI. XIX.
Quoted above.
37. Young Brissopsis, measuring 5.6 nan. in iliameter, from the abactinal side ; shows the huge ambulacral ten-
tacles (provided with suckers) of the odd ambulacral area, within the slightly dumb-bell-shaped peripetalous fasciole. The anal system is placed between the posterior edge of the abactinal and of the snbanal fasciole.
38. Profile of same, showing the bevelled anterior extremity of the test, surrounded by the peripetalous fasciole.
39. Peripetalous fasciole of a young specimen, measuring about 3.6 mm. in longitudinal diameter; 5 : 4 pairs of
simple pores in the anterior, and 4 : 3 pairs in the posterior lateral ambulacrum. There are from five to six simple pores in the odd anterior ambulacrum.
40. Peripetalous fasciole of an older stage, in which the fasciole has become undulating, and tlie lateral aujbu-
lacra somewhat petaloid.
EMBEYOLOGICAL M0:N"0GKAP1I.S,
PLATE xrir.
Development of Holothuroidea. Figures from Johannes Mulleu and Elias Metschnikoff.
1-11. Synapta {Auricularia with calcareous wheels).
1 3 4. From Joliaiiiics Miiller, Ueber die Larven uml die Metamoi-pliosc der Ecliiuodertnen, Zweite Abhandlung,
1848, PI. IV. Abliaudl. d. K. Akad. d. Wiss. Berlin, 1849.
2 5-11. From .loliainu'S Miiller, Ueber die Lai-ven und die Metanior[iliosen der Holothurien iiiid Asterien
(Ft. 3), (1849-50,) Pis. I., II., III. Abhaudl. d. K. Akad. d. Wiss. Berlin, 1850.
d". Passage of vibratile cord from the oral to the dorsal cord. Anus.
Dorsal pore.
Tentacular rosette of the water system. Tentacular lobes of the water system. Calcareous wheel.
1. Young Auricularia, seen from the ventral side.
2. Somewhat older Auricularia, seen from the ventral side.
3. Older stage, in which the arms are developed.
4. Somewhat older Auricularia ; the tentacular lobes of the water system, i, are well seen.
5. About in the same stage as the preceding, seen obliquely from the dorsal side.
6. Auricularia at the time of the metamorphosis ; the lateral arras have disappeared, and broad transverse
bands of vibratile cilia have been formed.
|
a. |
Mouth. |
d'l |
|
b. |
(Esophagus. |
e. |
|
c. |
Digestive cavity. |
9- |
|
c<. |
Intestine. |
h. |
|
d. |
Dorsal part of the siraple vibratile cord. |
i. |
|
d'. |
Oral part of the vibratile cord. |
0. |
7-11. Stjnapta, continued.
Digestive cavity. /.
Anal opening. g-
Circular ring of the water system. h.
Polian vesicle. i.
The five branches of the circular ring leading to k.
the tentacles. /.
Vesicles (otoliths) with gi-anules round the oral iii.
water-ring. n.
Tentacular chamber.
Canal with the crescent-shaped limestone arc. Lateral muscular bands. Calcareous gland at the anal extremity. Cavity in which the tentacles are developed. y rods of the or"al calcareous ring. Intestine.
Position of the cavity where the tentacles eventually break through.
e. Calcareous skeleton of the oral ring.
7. Synapta pupa, somewhat compressed, and somewhat older than the preceding stage.
8. Synapta pnpa, somewhat more advanced than the preceiiing stage.
9. Young creeping Synapta.
10. Young Synnpta, .somewhat compressed.
11. Young Synapta, still older, compressed.
In figs. 9-1 1 the tentacles of the young Synapta have forced their way through the actinal extremity of the pupa, and the broad transverse bands of vibratile cilia disappear with advancing development.
12-17. Synapta, continvM. From Elias Metschnikoff, Studien iibcr die Entwickelung der Echinodermen und Nemertincn, 1869, Pis. I., II. Mem. Acad. Imp. de St. Petersbourg, VIPSer., XIV., No. 8.
c. Cutis.
ce. Oisoph.agus.
c d. Cavity of the lateral disk.
d'. Left water-tube.
dr. Eight water- tube.
p a. Dorsal pore.
s. Stomach.
s c. Outer layer of the lateral disks. si. Inner layer of the lateral disks. <!-<*. First to fifth tentacular lobes of the oral ring of tentacles.
V a. Original pouch of the water system.
V I. Otoliths round the oral water-ring.
MEM. M. C. Z., IX. No. 2. — ECHINODEEMATA.
39
12. A' very young .\uricularia, with yellow pigment spots. This figure is not a j'ounger stage of the following
ones, which all belong tn Synapta.
13. Youn" Aurieulavia, in which the water system pouch and the lateral disks have not yet appeared.
14. Older Auricularia, in which the original ]iroblematic body has divided into two, forming the two lateral disks.
15. The lateral disks have now assumed their characteristic appearance, and the water system has become five-
lobed.
16. Somewhat more advanced ,\uricularia ; the water system shows a secondary set of smaller lobes between the
larc'er ones, and has taken a horseshoe shape ; the lateral disks have hicreased in size.
17. Shows the horseshoe-shaped water system, with a portion of the left water-tube.
Figs. 13-17 correspond to the period included between the stages figured by Miiller. See above, figs. 1-3.
18. Auricularia icifh calcareous ghmul. From Johannes Miillcr, Ueber die Larven und die Metamorphose der
Holothurien und Asterien (Tt. 3), 1849-50, PI. IV. Quoted above.
18. Auricularia, seen from the ventral side, a, mouth ; b, oesophagus ; c, digestive cavity ; d, intestine ; c, anus ;
/, calcareous gland ; f/, gray granulation covering/.
19. Auricula/ria with eleven qihercs. From Johannes Miiller (Ft. 3), PI. IV. Quoted above.
19. Adult Auricularia, seen from the oral side, a, mouth ; 6. oesophagus ; c, stomach ; c, problematic body
(lateral disk) ; y, depression in which the mouth is placed.
20- 23- 20-
20-32. Atiricularia with clastic sj)hc7xs,
■22, 29. From Johannes Miiller, Ueber die Larven und die Metamorphose der Echinodennen, Vierte Abhand- lung, 1850-51, Fl. I. Abhand. d. K. Akad. d. Wiss. Berlin, 1852.
■28, 30-32. From Johannes Miiller, Ueber den AUgemeinen Plan in der Entwiekelung der Echinodermen (Ft.
6), 1852, Pis. III., v., VI. Abhand. d. K. Akad. d. Wiss. Berlin, 1853. •21. Auricularise in the stage of devehipment preceding the cylindrical form. 20 is seen from the dorsal side, 21 from the ventral side.
/. Lobes of the oral tentacular system.
g. Calcareous ring of dorsal pore.
h. Water system.
hi. The eleven elastic spheres.
i. Calcareous gland.
0. Anus.
22.
the future madreporic
23. 24.
26. 27. 28.
29.
30,
a. Mouth.
b. (Esophagus.
c. Stomach. c'. Intestine. cl. Vibratile cord. e. Problematic bodies.
Auricularia somewhat younger than the preceding stages, at the time when the calcareous ring of the dorsal pore begins to form.
X. Part of the bilateral vibratile cord, which disappears.
I, II, III, IV, V. Portions of the bilateral vibratile cord, which become the first to fifth trans- verse ciliated bands.
3', 4'. Lobes of the dorsal part of the bilateral vibratile cord, which become part of the third anil fourth transverse ciliated band on the dorsal side.
Fully developed larva, of which the mouth and resophagus can still be seen. The bilateral vibi'atile cord is
in process of passing into the transverse ciliated band. A pupa without a mouth, seen obliquely from the ventral side ; on the ventral side oidy can the anterior part
of the bilateral vibratile cord lie recognized ; the posterior transverse ciliated Viands are fully formed. Another pupa without a mouth, seen from the dorsal side ; the transverse ciliated bands are not yet all
closed ; the first and second are not yet complete. A pupa shortly before the oral tentacles force their way through ; 1', dorsal part of the first vibratile cord, I. A pupa, still pelagic ; the tentacles have just forced their way through the anterior extremity. Somewhat older pupa, in which the membrane uniting the tentacles and connecting with the perisome is
developed. Young Holothuria, in which, besides the transverse ciliated bands, traces of the bilateral ciliated cord can
still be seen. \'oung Holothuria, with a ventral sucker, under compression, seen in profile, showing the ventral ambulacral
canal and its vesicle connecting the sucker with the circular canal.
|
a. |
Mouth. |
|
b. |
(Esophagus. |
|
c. |
Digestive cavity. |
|
d. |
Intestine. |
|
e. |
Anus. |
|
/• |
Tentacular system. |
|
?■ |
Calcareous ring of |
|
opening. |
|
|
0. |
Calcareous sphere. |
40 EMBRYOLOGICAL MONOGRAPHS.
31. Young Ilolothuria, aliovit in the stage of fig. 30 ; the vibratile cilia have ilisappeared, and the young Holothu-
lian now creejjs by means of its tentacles and ambulaeral sucker.
32. Young Ilolothmia, somewhat older, under compression, seen I'rora the dorsal side. The circular oral canal,
the stone canal, the Polian vesicle, and the ventral ambulaeral eanal, are well seen.
33-37. Auriculciria, v)ith dendritic and calcaremts gland.
33-35, 37. From .lohannes Miiller, Ueber die Larven und die Metamorphose der Holothuiien uud Asterien (Pt. 3),
1849-50, n. Y. Quoted above.
36. From .Johannes JliUler, Ceber die Larven und die Metamorphose der Echinodernien, Yierte Abhandlung,
1850-51, PI. I. Quoted above.
33. 34. Two successive stages of the pupa, under compression.
35. Holothurian larva of the same, with free tentacles, a, digestive cavity ; c, circular canal ; c', Polian vesicle ;
f", the five branches of the circular oral canal leading to the tentacle ; e, calcareous oral ring ; /, tentacles ; !7, stone caual, with its calcareous ring ; h, the lateral elastic spheres ; h', the odd terminal anal sphere ; i, the terminal anal dendritic gland ; I; the remnants of the vibratile cord ; I, transverse bands of vibra- tile cilia.
36. Somewh.at more advanced young Holothuria, with a small ventral ambulaeral sucker : the vibratile cilia of the
transverse bands have disappeared, d, the tentacular-like bodies at the base of the oral tentacles along the calcareous ring ; /, circular canal ; /', Polian vesicle ; g, stone canal and its calcareous ring ; o, extremity of the ventral ambulaeral canal.
37. Young Holothuria, in a stage intermediate between figs. 35 and 36.
MEM. M. C. Z., IX. Ko. 2.— ECHINODERMATA. 41
|
a. |
Anal opening. |
|
bh |
Blastoderm. |
|
eh. |
EctoJerra. |
|
e n. |
Entoderm. |
|
f. |
Segmental cavity. |
|
m. |
Mesoderm. |
|
m'. |
Exterior mesodermal plate. |
|
9h". |
Interior mesodermal plate. |
|
0. |
Mouth. |
|
w. |
Cord of vibratile cilia. |
|
X. |
Water-system pore. |
PLATE XIV.
Development of Holothuroidea, continued. Figures from Emil Selenka, and D. C. Daniels-
.SEN and J. KoREN.
1-12. Holoihuria tuhulosn. From E. Selenko, Zur Entwiclcelung der Holotluirien (Holotlmria tubulosa uud Cucumaria doliolum), Ein B.'itrag zur Kcimblattertheorie, 1876, Pis. I.X., X. Zeits. f. Wiss. ZooL, XXVII.
A. (Esojihagus.
B. That part of the digestive cavity from which the vasoperitoneal sac has separated.
H. Stone canal.
N. Nucleus.
P. Peritoneal sac.
Pr. Right peritoneal sac.
PI . Eeft peritoneal sac.
u. Original digestive cavity of larva.
v. Water-system sac.
V2'- Vasoperitoneal sac.
1. Six hours after fecundation. Optical section. «, nucleolus ; a, membrane of egg.
2. Blastula, fifteen hours after segmentation ; tlie segmentation is nearly complete, s, spermatozoon ; m, mi-
cropyle. Many of the blastoderm cells already have a ciliated lash. The blastoderm rotates slowly and irregularly within the egg membrane.
3. Gastrula, twenty-three hours after fecundation ; longitudinal optical section. Commencement of the invagina-
tion ; a few cells, the mesoderm, have separated from the ectodenu ; the egg membrane has been ruptured, and has disappeared.
4. A transparent larva, seen from the ventral side, forty-four hours after fecundation ; the digestive cavity, u,
already shows a constriction, the point of subseipient separation of the vasoperitoneal sac from the distal e.xtremity of the digestive cavity. E, green bodies of the vibratile cord containing cells.
5. Optical section of a larva, fifty-one liours after segmentation ; the vasoperitoneal sac, Vp, has become sepa-
rated from the anal part of the digestive cavity, B.
6. Diagrammatic profile view of the same larva. Formation of an atrium, A, the future oesophagus, by inva-
gination of the blastodei-m. Tlie vibratile cords and mesoderm cells have not been drawn.
7. Optical section of a larva, sixty-nine honrs after segmentation, seen from the dorsal side, b, blood cells in the
vasoperitoneal sac ; R, the green granules, containing cells of the vibratile cord ; p, contents of the digestive cavity. The oesophagus and intestine are now connected ; the vasoperitoneal sac is pushed to the left side.
8. The transparent larva, seventy-one hours after fecundation, sf, vertical axis of the larva when swinnning
in a natural attitude, and round which it slowly rotates, moving forward in long spirals at tlie same time.
9. The transparent larva, a hundred hours after the fecundation. The vasoperitoneal sac has divided into three
distinct sacs, the water-system sac, and the two lateral disks.
10. Diagi-anmiatic profile view of fig. 8.
11. Diagrammatic profile view of fig. 9 ; a few mesoderm cells, g, round the stone canal, a-, have been indicated.
12. Sketch of the digestive cavity and the surrounding parts of the same larva (fig. 9), a few hours later (seven
hours).
13-27. Uolothiiria tremuJa. From D. C. Danielssen and ,T. Koren, ..Observations sur le Developpement des Holothuries, 1856, Pis. VII., VIII. In Fauna littoralis Xorvegiffi, par Dr. M. Sars, J. Koren, et D. 0. Danielssen, Seconde Livraison, 1856, Pis. VII., VIII.
13. Young embryo, recently hatched ; still covered with vibratile cilia.
14. Somewhat older embryo, with a mouth opening, a.
42 EMBRYOLOGICAL MONOGRAPHS.
15. Slightly older than the iireceding figure, b, stomach.
16. Young embryo, in which tlie deincssion b indicates tlie point where the five tentacles are to force their
way through.
17. Embryo, somewhat compressed, to show the calcareous ring, a, round the base of the stone canal, b.
18. Embryo, seen from the ventral side, compressed, o, mouth ; b, circular ambulacral ring ; c, the five primary
anibulacral tentacles ; d, the five small calcareous tentacular appendages of the circular canal ; e, the stone canal.
19. Embryo, seen from the mouth side, a, mouth; /), depression for the five primary ambulacral tentacles of
the circular canal ; c, depression for the passage of the first pair of ventral ambulacral tentacles. ■20. Emlnyo, seen from the ventral side, compressed, a, mouth ; b, circular vascular ring ; c, ambulacral tentacle.
21. Embryo, in which tlie oral tentacles have forced their way through ; seen from the dorsal side, with the tenta-
cles protruded.
22. Embryo, about iu the stage of fig. 21, seen from the side, compressed, a, mouth ; I, circular canal ; c, oral
tentacle ; d, stone canal ; e, Polian vesicle ; /, stomach ; g, intestine.
23. Young embryo, somewhat older tlian the stage of fig. 21, seen in profile.
2i. Embryo, about in the stage of fig. 23, seen in profile, under compression, a, mouth ; b, digestive sac ; c, anal, and d, oral tentacles ; c, the vesicles of the circular vascular ring at the base of the oral tentacles ; /, calcareous oral ring ; ff, the five longitudinal water-canals ; h, water-tubes leading to the base of the ambulacra ; i, ambulacral tentacles of the ventral side ; k, Polian vesicle ; I, stone canal ; ni, circular oral vascular ring.
25. Young embryo, seen from the dorsal side, with the first-formed five oral anibulacral tentacles branching, and
with five new tentacles placed in between them.
26. Embryo, about in the stage of fig. 25, seen from the mouth side under compression, a, the ten oral ti-ntacles ;
b, mouth ; c, membranous ring round the actinostome ; (I, outline of the oral calcareous ring ; c, circular water-ring ; /, Polian vesicle ; g, longitudinal water-canal ; k, branch of water-caiial leading to the ventral ambulacral suckers ; i, ventral ambulacral suckers ; !c, transverse muscular bauds ; /, longitudinal muscu- lar bands ; m, stone canal ; n, anus.
27. Embryo, seen from the dorsal side, with three pairs of ventral ambulacral tentacles, and ten branching oral
tentacles.
MEM. M. C. Z., IX. No. 2. — ECHINODERMATA
43
PLATE XV.
Development of Holothuroidea, continued, and Comparison of Echinoderm Larvae. Figures from Emil Selenka and Johannes Muller.
1 - 13. Cucumaria doliolmn. From E. Si-U'iika, Zur Entwickelung Jer Holothurien (Holotluiria tubulosa uud Cucumaria iloliohim), Ein Beitrag zur Keiinlilattei-tlieorie, 1876, Pis. XL, XII. Zeits f. Wiss. ZooL, XXVII.
|
a. |
Anal opening. |
|
bl. |
Blastoderm. |
|
cl: |
Ectoderm. |
|
c n. |
Entoderm. |
|
/■ |
Segmental cavity. |
|
711. |
Mesoderm. |
|
m'. |
Outer mesoderm plate. |
|
m". |
Inner mesoderm plate. |
|
0. |
Mouth. |
|
u\ |
Cord of viliratilc cilia. |
|
X. |
Water-system pore. |
|
A. |
CEsophagua. |
|
B. |
Stomach from which has separated the vaso- |
|
peritoneal vesicle. |
|
|
H. |
Stone canal. |
|
K. |
Nucleus. |
|
P. |
Peritoneal sac. |
|
Pr. |
Right peritoneal sac. |
|
PI. |
Left peritoneal sac. |
|
u. |
Original digestive cavity of larva. |
|
V. |
Water-system sac. |
9
F^). Vasopeiitoneal sac.
1. Egg found floating on the smface, in process of segmentation, n, genninative vesicle.
2. Completely segmented blastula. s, the part of the blastoderm where the invagination will take place.
3. The biastula has become larger, a, position of the future anus ; m, mesoderm cells.
4. Gastrula at the end of the second day ; longitiulinal section. The migratory cells have accumulated in part
towards the ectoderm at d, to form later the circular muscular system, and in part remain five in the seg- mental cavity, s, the part of the blastoderm where the invagination to form the digestive cavity can be traced by the slight depression at that pole.
5. Longitudinal section of an older gastrula.
G. Sagittal section of larva at the end of the fourth day.
7. A', £', C, show the mode of formation of the water system, and of the two peritoneal sacs as diverticula
from the original digestive cavity ; 7t, the poiut where the fully formed invaginated cesophagus strikes the digestive cavity.
8. Free swimming embryo. |, oil globule of the head. Section of a larva, about in the stage of fig. 8. Lettering as before, with the following additions : —
U. Circular vascular ring, with the five oral tentacular vesicles.
F. The five ambulacral canals.
G. The ventral ambulacral canal, with two ambulacral tentacles. X, Stone canal.
J. Spheres of food in the stomach.
K. Anterior lobe of embryo.
P'. Wall of the peritoneal sac.
S. Cells with lashes, originating from the Wbratile cord.
+. Polian vesicle. (This is cut off. )
10. Older embryo, swimming freely.
T. The five oral tentacles, which can be nearly entirely contracted.
0. The two ventral ambulacral tentacles, with inidimentary sucking disks.
J. Oil globule in anterior part of the head.
11. Young Cucumaria creeping. The bands of vibratile cilia have disappeared ; the anterior portion of the young
Cucumaria is rounded, and the oil globule of the interior has been resorbed. D, ventral ambulacral ten- tacles, with calcareous sucking disks ; S, calcareous plates of the ectoderm.
44 EMBEYOLOGICAL MONOGRAPHS.
12-13. Abnormal Blastula: of IMothvria tuhiiln»i. From E. Seleiika, Zur Entwickelung der Holothurieu, 1876,
ri. XIII. Quoted above.
14-27. Homologies of EchiiwdcTm Larva:. From Jobaiiues llUller, Ueber den Allgemeinen Plan in der Entwicke- lung der Ecbinodermen, Pt. VI., 1852, PI. II. Quoted above. Anterior or oral jilastron.
Posterior or anal plastron, iti which is placed o, the anal opening. Intei-raediate oral area, in which is ijlaccd C, the mouth, and a, the anterior, i, the posterior edge of
the transverse part of the oral ribratile cords ; c, the connecting vibratile cord between the oral
and anal plastrons. Posterior lobe of the vibratile cord of the oral i)lastron. Anterior lobe of the vibratile cord of the anal plastron. Arms of the anterior and posterior plastrons on the oral side. Arms of the anterior and posterior part of the dorsal vibratili^ cord.
Processes forming in Echini arms at the anal extremity, not in the line of the vibratile cord. Connecteil vibratile cord of the dorso-anal system. Conni^cted vibratile cord of the oral ventral plastron. Brachiolarian appendages of the Starfish larva. The whole of the P.rachiolaria of fig. 27, beyond
the braehiolarian arms, corresponds to the Starfish larval organ, such as has been figured by Sars,
Thomson, Ludwig, and others.
14-16. Shows the development of an Auricularia from the tj'pical Echinodermal larva, fig. 14.
17-19. The development of an Ophiuran Pluteus from the typical Echinodermal larva, fig. 17.
20-23. The development of an Echinoid Pluteus from the typical Echinodermal larva, fig. 20.
24-27. The development of a Starfish Brachiolaria from the tyi>ical Echinodermal larva, fig. 24.
For modifications of the typical form of development of the Holothurians, see PI. XIV. figs. 13-27, PI. XV.
figs. 5-11. For modifications of tlie typical form of development of the Opliiurans, see PI. III. figs. 1-20, 26-31. For modifications of the typical form of development of the Starfishes, see PI. V. figs. 1-4, 15-49, PI. A'l. For modifications of the typical form of develojuuent of the Sea-urchins, see PI. XII. figs. 30-34.
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II^DEX.
Amphiura ? PI. Ill
AmjMura squamata, PI. III.
Aiiledon Larva, Fl. II
Arbacia puiictulata, PI. IX.
Arbacia pustulosa, PI. IX.
Astcracanthion bcrylimis, F\. VII.
Asteracanthion flaccida, PI. VI.
Astr.racmithion pallidus. Pis. VII., VIll.
Asteracanthion violaccus, PI. VI. .
Astcrias glacialis, PI. VIII.
Asterina gibbosa. Pis. V., VI.
Asteroidea, Development of, Pis. V.-VIII. .
Asthcnosoma hystrix, PI. XII.
Auricularia with calcareous wheels, PI. XIII.
Auricularia with calcareous gland, PI. XIII.
Auricularia with eleven spheres, PI. XIII. .
Auricularia with elastic spheres, PI. XIII.
Auricularia with dendritic anal gland, PL Xlll.
Bipinnaria nsterigera, PI. VIII. Brisso^ms lyrifcra, PI. XII.
Crinoidea, Development of, Pis. I., II. . Comatula, Pis. I., II., ....
Comatula rosacea. Pis. I., II. ...
Comatula mcdilcrranea, PI. I. . Conolampas Sigsbei, PI. XII. .... Cucumaria doliolum, PI. XV. . . . .
Diadema setosum, PI. XII.
Dorocidaris papillata, PI. XII. ...
Echiuarachnius parmn. Pis. XI., XII. . Echinaster sanquinolentus, PI. VI.
Echinastcr Sarsii, PI. VI
Echinaster seposittis, PI. V. ...
Echinoidea, Young Stages of, PI. XII. Echinoeardium cordatum, PI. IX. Eehinocyamus pusillus, PI. XI. Echinodenn Larva:, Homologies of . . .
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Echinoidea, Development of, Pis. IX.-XII. Echinoid Pluteus, Pi. XI. .... Echinus acutxis, PI. XI. .... Echinus brevispinosus, PI. XI. Echinus lividus, PI. XI. .... Echinus niiliaris, PI. IX. .... Encope emarginata, PI. XII.
Gonioddaris canaliculata,'P\. X\l.
Hcmiaster cavcrnosus, PI. XII. . . Holothuria trennila, PI. XIV. Solothuria tubulosa, PI. XIV. Holothuroidca, Development of, Pis. XIII. -XV. Homologies of Echinodenn Larva:, PI. XV. .
Mellita longifissa, PI. XII.
Mellita sexforis, PI. XII. . . . .
Mellita testudinata, PI. X 1 1. . .
Ophiocoma rosula, PI. III. .
Ophioph^lis ? PI. Ill
Ophiojiholis bellis ....
Ophiothrix fragilis, PI. IV. . Ophiothrix versicolor, PI. IV. Ophiuroidca, Development of. Pis. III., IV.
Pluteus bimaculatus, PI. IV. .' Ptcraster militaris, PI. VI.
Spatangoid Pluteus, PI. XI. . Spatangus jmrpurcus. Pis. XL, XII. . Strongylocentrotus Drbbachinisis, PL X. Strongylocentrotus lividus, PI. I.K. Synapta, PI. XIII.
Viviparous Ophiurans, PL III. .
Wurmformige Aster ic, PL VI.
Young Stages o{ Echiiwidea, PL XII. .
PAGE
28-37 . 34
35 . 35
35 . 28
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EMBRYOLOGiCAL MEMOIRS
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