70 



Reproduction and Life-Cycles 



The C-shaped macronucleus of Euplotes (Fig. 2. 13, A-D) is shortened 

 and thickened, and undergoes changes in staining reactions which sug- 

 gest progressive internal changes. The two macronuclei of Stylonychia 

 pustiilata (227) fuse into a single body which then divides. The macro- 

 nuclear chains of Spirostornum, Stentor, and Blepharisma also undergo 



Fig. 2. 12. Elimination of chromatin during macronuclear division in 

 Colpidium colpoda. A. Central chromatin mass evident just before divi- 

 sion. B-E. Stages in division. F. Separation of discarded mass from a daugh- 

 ter macronucleus. A-E, x510; F, x700 (after Kidder and Diller). 



extensive condensation. In Spirostomiim ambiguum (22) and Stentor 

 coeriileiis (238) the macronuclear nodes gradually fuse into a compact 

 central body, which then undergoes moderate elongation and a final 

 constriction (Fig. 2. 13, E-I). In Blepharisma imdiilans, the anterior and 

 posterior macronuclear nodes fuse into two masses, while the middle 

 nodes gradually disappear. The anterior and posterior masses then fuse 

 into one body which elongates and undergoes division (238, 255). 



