386 



ZOOLOGY 



to the;'gonads, which are to be looked upon as the greatly expanded 

 extremities of the latter. Strands of the lacunar tissue accompany 

 the genital rachis and its branches to the gonads. 



Reproductive System. — The Starfish is unisexual, each in- 

 dividual possessing either ovaries (Figs. 308, 309, and 310, 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. 

 Ova and sperms are alike developed from cells of the same 

 character as those which become the amoebocytes of the ccelomic 

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

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



card, si P'A^-^ ^ ^a^ 



p(/Lcccc 



ri^. 



Fig. 310. — Anthenea flavescens. Lateral view of a dissection in which one of the rays and 

 a portion of a second have been remo'ved, and in which the alimentary canal has been laid 

 open. a?)2p. arapuUai ; ml. anus ; card. St. cardiac pouch of the stomach ; int. ccec. intestinal 

 CEecum ; ip. inter-radial partition ; viad. madreporite ; mad. can. madreporic canal ; ov. ovary : 

 pTfl. cac, pyloric casca ; r. cut ends of the ring- vessel of the ambulacral system ; ring v. posi- 

 tion of the ring-vessel ; reir. retractor muscle of cardiac pouch of stomach ; s. cavity of the 

 stomach. 



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. 308, 310, 311, 312), a common 

 Australian Starfish, which may be taken as an example instead of 

 Asterias ruiens, 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 oral surface the comparatively broad, flat surfaces be- 

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

 ossicles being beset with a number of minute rounded tubercles, 

 which, in the immediate neighbourhood of the ambulacral 

 grooves, assume the character of short, blunt spines. Here and 



