74 



SPONGES 



some parenchymulae paves the way for an important variation in the 

 mode of formation of the inner mass. We have seen that in Cl. blanca 



53 



H 



mal (con- 

 ractile) 

 pithelium 



$1 







'~ a 



<U r-l g 



O 



<* ^ 



s 



11 



- .s 



" 





O OT 



-J U 



6 



PH 



immigration of cells takes place at any point. When there are no pos- 

 terior granular cells, however, the immigration may be entirely restricted 

 to the posterior pole, so that the hindermost flagellated cells become con- 



