182 



PORIFERA 



CHAP. VII 



Saville Kent, and since rediscovered both in England and 

 abroad. 1 This is a colony of unicellular individuals embedded 

 in a common jelly. The individuals at the surface are 

 choanoflagellate, while in the interior the cells are rounded 



Fig. 75. Proterospongia haeckeli. a, Amoeboid cell ; b, a cell dividing ; c, cell 

 with small collar ; z, jelly. x 800. (After S. Kent. ) 



or amoeboid, and some of them undergo multiple fission to form 

 reproductive cells. This is just such a creature as we might 

 imagine that ancestral stage to have been of which the free- 

 swimming sponge larva is a reminiscence : for we have seen 

 that the flagellated cells of the larva are potential choanocytes. 

 1 France, Organismus der Craspedomonaden, Budapest, 1897, p. 217. 



