PHYLUM PORIFERA 



103 



FIG. 62. Venus' flower-basket. The skeleton of a sponge, Eupleclella. 



(From Weysse.) 



to appear." Sense cells are supposed to have developed next 

 as we find them in ccelenterates (p. 112), and finally a central 

 organ was added, completing the neuromuscular mechanism 

 as it exists in higher METAZOA. 



(3) Reproduction. - - Reproduction is either asexual or sexual. 

 By the asexual method there are produced buds and gemmules. 

 Buds may be set free to 

 take up a separate existence, 

 or may remain attached to 

 the parent sponge, aiding in 

 the formation of a complex 

 assemblage of individuals. 

 Gemmules are formed as de- 

 scribed in Spongilla (p. 99). 



In sexual reproduction the 

 eggs and spermatozoa are 



m FIG. 63. The bath sponge, Euspongta 



derived as in SyCOn (p. 96) offirinalis. (From Lankester, after Schulze.) 



