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 



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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- 



