356 



ZOOLOGY 



SECT.. 



Functionally the ovoid gland, with its dependencies, appears to 

 be an organ for the production of the amoeboid corpuscles* which 

 abound in the ccelome and the ambulacral system. This function 

 it shares with the Polian vesicles and Tiedemann's vesicles. 

 Morphologically it is a genital stolon; the narrow prolongations 

 which pass to the genital organs being so many genital rachides, 

 the expanded extremities of which form the ovaries or testes. 



Reproductive System. The Starfish is unisexual, each in- 

 dividual possessing either ovaries (Figs. 283 and 284, ov) or 

 testes, which appear very similar until they are examined micro- 

 scopically. They consist of masses of rounded follicles, like 

 bunches of minute grapes a pair in each inter-radial interval. 



pyl.ccec 



cunf} 



FIG. 284. Anthenea flavescens. Lateral view of a dissection in which one of the rays ; 

 a portion of a second have been removed, and in which the alimentary canal has been laid 

 open; amp. ampullae; an. anus; card. st. cardiac pouch of the stomach; ii>t. cose, intestinal 

 csecum ; ip. inter-radial partition ; mad. madreporite ; m<l. <,!. madreporic canal ; or. ovary; 

 pyl. ccec, pyloric cseca ; r. cut ends of the ring-vessel of the ambulacral system ; ring r. posi- 

 tion of the ring-vessel ; retr. retractor muscle of cardiac pouch of stomach ; .*. cavity of the 

 stomach. 



Ova and sperms are alike developed from cells of the same 

 character as those which become the amcebocytes of the coelomic 

 and other cavities of the body. The ducts, by means of which 

 the ova or sperms reach the exterior, open on the dorsal surface 

 through a number of perforations on a pair of sieve-like plates, 

 situated inter-radially close to the bases of the arms. 



Anthenea flavescens (Figs. 283-286), a common Australian star- 

 fish, which may be taken as an example instead' of Asterias rubens, 

 differs from the latter in the following main points. 



The animal consists of a relatively large central disc and five 

 relatively short arms, which taper rapidly towards their extremities. 

 On the ventral surface the comparatively broad flat surfaces be- 

 tween the ambulacral grooves are rougLish, owing to the plate-like 



