PHYLUM PORIFERA 



103 



Fig. 62. — Venus' flower-basket. The skeleton of a sponge, Euplectella. 



(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 



derived as in SyCOfl (p. 96) officinalis. (From Lankester, after Schulze.) 



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