Fi<;. 407. Older Auricu- 

 laria (after Semon). an, 

 Anus ; os, mouth ; 1, out- 

 growths (primary and 

 secondary) of the primitive 

 lior.se - shoe - shaped hydro- 

 ccel ; 2, stone canal ; 3, left, 

 4, right enterocoelomic sac, 

 which have become closely 

 applied to the mid-gut. 



FIG. 40S. Auricularia, 

 in which the circumoral 

 ciliated ring is beginning 

 to break up into lengths 

 (after Semon). The horse- 

 shoe - shaped hydroco?! is 

 growing round the intestine. 

 The first pieces of the cal- 

 careous ring (1) have ap- 

 peared. 



VOL. II 



2 L 



