PHYLUM PORIFERA 



97 



body-wall. Both eggs and sperms occur in a single individual; 

 i.e. Grant la is moncecious or hermaphroditic. The development 

 of the fertilized egg has been observed in Sycon (Fig. 57) and is 

 probably similar to what occurs m-Grantia. The egg (a) seg- 



FIG. 57. Development of a simple sponge, Sycon. a, ovum ; b, c, ovum 

 segmented; d, blastula; e, amphiblastula; f, commencement of invagination; 

 g, gastrula attached; h, i, young sponge. (From Parker and Haswell, after 



Schulze.) 



H 



