TROCHOPHORE OF HYDROIDES UNCINATUS (eUPOMATUS). 573 



steps by whicli the larger of the two cells is shifted back 

 into the anal region are somewhat difficult to follow. Some- 

 times they do not appear to differ greatly from the surround- 



Text-fig. 24. 



m. 



Kkr 



aa.v.' 



24- 



Diagrammatic figure of an early troehophoi'e of Eiipomatus 

 liefore the formation of the mesol;)last bands, and showing the 

 opening of the head-kidney into the proetodsenm. rce.m. Coelo- 

 mesoblast. an. Anus. an. v. Anal vesicle. mesc. Mesen- 

 chyme or ectomesoblast. /(A-. Head kidney. */(. Mouth, stvic. 

 Stomach. 



ing cells, but they can usually be distinguished by their 

 greater affinity foi- stains; and in late stages they can 

 always be recognised by the way they are wedged into the 



