THE INFUSORIA 197 



In all cases the tentacles are remarkably like pseudopodia, and may 

 change their form and their position, and may even be entirely with- 

 drawn into the body, to reappear, possibly, at some other place. 

 Some forms have the power of withdrawing their tentacles and 

 developing cilia, which may be retained for a longer or shorter 



Fig. 109. Dendrosoma radians Ehr. [SAVILLE KENT.] 

 n, nucleus. 



period. In some cases the tentacles distinctly originate in the endo- 

 plasm, and penetrate the membrane (Hertwig, '76; Ishikawa, '96). 



The nuclei, like those of the Ciliata, are of two kinds, macro- and 

 micronuclei. The former are little different from the macronuclei 

 of the more generalized Ciliata, while very little is known about the 

 latter. In the colony-form Dendrosoma, where the many branches 

 suggest a hydroid colony, the macronucleus extends through all the 



