ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 



155 



There are similar colourless stages ; these never become green ; they 

 seem to be dead. Except in finding some protection the Algae are not 

 benefited by their association with the sponge, and the protection is 







Particles in layer of circulating protoplasm lying against the base of 

 the choanocytes on the side of the incurrent canal. 



t 



p/*' 







Capture of a coarse food particle by means of the layer of 

 streaming plasma. 



limited, for the sponge is always destroying them. To the sponge they 

 afford useful food, being digested in the amoebocytes. The significance 

 of the oxygen, produced by the green Algae does not seem to be greafc. 

 In the spiral movement of the flagellum of a choanocyte there is a very 



