MEM. M. C. Z., IX. No. 2,— ECHINODERMATA. 19 
PAT AV IE Vill: 
Development of AsTERoIDEA, continued. Figures from Husert Lupwic, Louis Acassiz, MicHarL 
Sars, C. Wyvitte Tuomson, Jonannes Miier, and J. Koren and D. C. Danienssen, 
1- 
) 
- 
11. Asterina gibbosa, continued. 
A,. First ambulacral plate. 
Ay. Second ambulacral plate. 
A d,. First adambulacral plate. 
A dy. Second adambulacral plate. 
Af. Anal opening. 
Bl. Blood system. 
c. Centrodorsal plate. 
D. Diyestive cavity. 
Ec. Enteroccelum. 
F. Terminal tentacle. 
F,. First pair of tentacles. 
Fy. Second pair of tentacles. 
He. Hydrocelum. 
Ja. \nterambulacral plates. 
Jm. Intermediate plates. 
From H. Ludwig, Morphologische Studien an Echinodermen II., 2 Heft, 
1882. Zeits. f. Wiss. Zool., XXXVII., Pls. VII., VIII. 
JRy, J Ry J Ry, SRy J Rs First to fifth interradial 
Wi 
ym. 
M. 
Ms. 
17, 
Ss. 
St. 
plates. 
Interradial space of the larval organ. 
Interradial space of the madreporie plate. 
Mesentery. 
Mesoderm. 
Dorsal pore. 
(sophagus of Starfish. 
Stone canal. 
Ty, T2,T3, Ty, Ts. First to fifth terminal plates. 
I, 2, 3, 4, 5, denote the hydroccelum and ambula- 
cral lobes. 
TZ, II, III, IV, V, denote the antiambulacral arm- 
lobes. O denotes the upper extremity ; U, 
the lower; V, the anterior; H, the poste- 
rior; L, left; 2, right. 
. Larva at the end of the ninth day, seen from the dorsal side of a young Starfish. The abactinal region is rep- 
resented as transparent, to show the five lobes of the digestive cavity, the centrodorsal plate C, the five inter- 
radials JR, - J R;, and the five termin 
5» 
arms) is represented by a. 
3 of the hydrocelum ; @b, remnants of the larval organ. 
nally. 
fish is not yet formed. 
Transverse section of a larva in the stage of fig. 2. 
al plates 7\-7';. The remnant of the larval organ (the brachiolarian 
Larva of the tenth day, seen from the anterior extremity ; the optical section passes through the lobes 1 and 
The ambulacral arm lobes 2 and 3 have been eut longitudi- 
A young Starfish at the end of the tenth day, after the reduction of the larval organ a; the mouth of the Star- 
Young Starfish of the tenth day, seen from the abactinal side ; a, larval organ ; Y/, interradial space of the 
larval organ ; Ym, interradial space of the madreporic body. 
. Section across a young Starfish of the eleventh day, close to the actinal side. The water-ringis not yet closed ; 
at a are the two diverticula of the water system, which unite ina subsequent stage ; the section passes 
through the three-lobed digestive cavity, Ss; this does not yet open externally. 
. Exterior view of the soft parts of an arm of a young Starfish, in the thirteenth day. NV, rudimentary nervous 
ring ; B, swelling at the base of the terminal tentacle, where later an eye develops. 
. The same as fig. 7, to show the course of the ambulacral canal, the tentacles, and their position with respect 
to the terminal, the ambulacral, and the interradial plates. 
Starfish of the sixteenth day, seen from the actinal side, to show the general arrangement of the hard parts. 
. A 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 4 f, the odd terminal tentacle 7, 
extending beyond the edge of the disk ; S, 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 
ececa of the old Starfish ; 4, rest of the larval mesentery ; S'y, the five interbrachial septa ; Bs, the inter- 
radial ccecum of the end of the alimentary canal. 
