124 COMPAEATIVE ANATOMY. 



arrangement therefore is exactly tlie 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 an'anged in just the same way as 

 in the hermaphrodite Anthozoa, 



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

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

 change in form in consequence of amoeboid movements. The 

 seminal elements in the Acaleph^e are formed by a small head with 

 a movable appendage. 



