148 



PHYLUM ECHINODERMATA. 



be seen, are developed on the aboral side, but over the left 

 hydrocoel. 



mp 



FIG. 104. The just metamorphosed starfish of Asterina gibbosa, about ten days old ; A oral 

 view; B aboral view (from MacBride, after Ludwig). amb ambulacral ossicles; 1-5 the 

 lobes of the hydrocoel ; A-E the arms ; 6 the basal plates ; c the central ; mp the mad- 

 reporic pore ; T the terminals. 



The development of Asteroids with a bipinnaria larva is very similar 

 to that of Asterina. The principal difference seems to consist in the 

 fact that in bipinnaria (Goto, Bury, Field, op. cit. ) the coelom early becomes 



lf>.C 



snip. 



Lees. ..../' 



snt.C 



FIG. 105. Longitudinal vertical section through a metamorphosing larva of Asterina gibbosa 

 (after an original drawing by E. W. MacBride). The section passes through the interradius 

 of the preoral lobe and through the opposite radius, and shows that the preoral lobe of the 

 larva is attached to the oral surface of the adult, ad. in. adult mouth ; amp. ampulla of 

 a tube-foot; ant.c. anterior coelom in the preoral lobe; ii/t./i.r. internal perihaemal ring- 

 canal ; l.oes. vestige of larval oesophagus; l.p.c. left posterior coelom; p.or.c. perioral 

 coelom; pyl. pyloric sac; r. />./. right posterior coelom; slum, stomach; t.f. tube-foot; 

 w.v.ring water-vascular ring canal. 



completely double (Fig. 106), whereas in Asterina the anterior coelom is 

 single from the first, the posterior alone being double. Later, after the 

 division of the coelom into anterior and posterior in bipinnaria, the two 



