Explanation of Plate II. 



Fig. i. Transverse seclion through the upper part of the sphincter of Ad- 

 amsia tricolor. 



Fig. 2. Transverse section through the lower part of the sphincter of Ad- 

 amsia tricolor. This figure was drawn under higher magnifica- 

 tion than the preceding one. 



Fig. 3. Transverse section through mesenteries of the first and third cy- 

 cles of Sagartia spongicoLi. 



Fig. 4. Transverse section through the sphincter muscle of Sagartia 

 spoil gicola. 



