Fig. 407.— Older Auricu- 

 laria (after Semon). an, 

 Anus; os, month; 1, out- 

 growths (primary and 

 secondary) of the primitive 

 Iiorse - slioe - shaped hydro- 

 coel ; 2, stone canal ; 3, left, 

 4, right enterocoelomic sac, 

 which have become closely 

 applied to the mid-gut. 



Fk:. 408. — Auricularia, 

 in which the circumoral 

 ciliated ring is beginning 

 to break up into lengths 

 (after Semon). The liurse- 

 shoe - shaped hydroccel is 

 growing round the intestine. 

 The first pieces of the cal- 

 careous ring (1) liave ap- 

 peared. 



VOL. II 



