MEM. M. C. Z., IX. No. 2. —ECHINODERMATA. 
25 
BA AVIUB Valet Te 
Development of AstERorDEA, continued. Figures from ALEXANDER AGaAssiz, JOHANNES Miter, 
and S$. Loven. 
Anus. 
Dorsal or water pore, madreporic opening. 
Alimentary canal. 
Digestive cavity. 
Abactinal water-tubes in the angle of the rays 
of the young Starfish. 
Eye of Starfish at the base of the odd tenta- 
ele (//). 
Dorsocentral plate. 
Interradial plate. 
brachial terminal plate. 
Mouth. 
Opening for passage of ambulacral 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 surface 
of the rays. : 
Central spine of the abactinal surface of the 
young Starfish, with centrodorsal plate (7). 
Different forms of pedicellariz. 
Plate at the junction of adjacent rays (ovarian 
plate). 
Abactinal surface. 
7, 
ll. 
ul. 
Ww. 
First set of five limestone y rods which appear 
on the abactinal surface, and eventually be- 
come the terminal brachial plates (72). 
Second set of five y rods to appear on the 
abactinal surface, and which eventually be- 
come the interradial plates (7’). 
The first to fifth arm-lobes of the young Star- 
fish, 7! being the ray nearest the madre- 
porie opening. 
Actinal surface. 
Tentacles or water-system lobes of the young 
Starfish. 
Odd terminal tentacle. 
Ambulacral tube. 
First to fifth lobes of the water system, corre- 
sponding to the first to fifth arm-lobes of 
the young Starfish (r1=r), 
Lateral ambulacral plates, surmounted 
spines. 
Median ambulacral plates, carrying very small 
spines. 
Water-tube upon which the abactinal area de- 
velops. 
Water-tube communicating with the madre- 
poric opening, upon which the actinal area 
is developed. 
by 
1-23. Asteracanthion pallidus, continued. From Alexander Agassiz, Embryology of the Starfish, 1864 (Agass. 
Cont-Nat. Hist) U./S:, V.)} Pls. Vi, Vi., Vil; VILL 
American Starfishes, 1877, Pls. V., 
VALS Vel Levene 
Mem. Mus. Comp. Zodl., Vol. V., No. 1, North 
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 Pl. VII. fig. 31; figs. 5-7 are stages of development of the young Starfish which are only 
found on fully grown Brachiolarie, and in which, 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 whieh is developed the actinal area. 
3. Represents the opposite profile of the anal extremity of the Brachiolaria, showing the water-tube upon which is 
developed the abactinal area. 
4, 7. Represent the ventral side of the anal extremity of the Brachiolaria, showing the extremities of the actinal 
and abactinal areas of the Starfish. 
5. Represents the dorsal side of the anal extremity of the Brachiolaria, showing the opposite extremities of the 
actinal and abactinal areas of the Starfish. 
Owing to the transparency of the Brachiolaria, 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. 
