REPRODUCTION 



219 



posterior differentiation, the anterior part usually bearing the mouth 

 and the more or less specialized motile organs for the capture of food 



Fig. 109.— Uroleptus mobilis. Stages in the fusion of the macronuclei prior to cell 

 division; rnicronuclei in mitosis. (After Calkins.) 



or the directing of food currents, while the posterior part is usually 

 much less specialized. Should such a specialized ciliate be cut 

 through the center as Balbiani (1888) did for the first time, the two 



