124 COMPARATIVE ANATOMY. 



arrangement therefore is exactly the same as in some of the 

 Anthozoa, and if we compare the body-substance between two 

 radial canals with a septum of the Anthozoa, we find that the 

 genital regions of both sexes are arranged in just the same way as 

 in the hermaphrodite Anthozoa. 



As a rule the ova of the Ccelenterata have no special coverings, 

 and in many Spongias and Hydroida (e.g. Hydra) they appear to 

 change in form in consequence of amoeboid movements. The 

 seminal elements in the Acalephas are formed by a small head with 

 a movable appendage. 



