REPRODUCTION 



153 



Fig. 76. Conjugation of Metopus es (Noland). a, early stage; b, first 

 micronuclear division; c, d, second micronuclear division; e, third 

 micronuclear division; f, migration of pronuclei from one conjugant 

 into the other; g, large conjugant with two pronuclei ready to fuse; h, 

 large conjugant with the synkaryon, degenerating pronuclei and 

 macronucleus; i, large exconjugant with newly formed micronucleus 

 and macronucleus, showing the degenerating old macronucleus; j, 

 small exconjugant with degenerating macronucleus; k-m, develop- 

 ment of two nuclei, a, X290; b-j, X 250; k-m, X590. 



but two of the many problems which numerous investigators at- 

 tempted to solve since the appearance of the first comprehensive 

 study of the phenomenon by Maupas in 1889. Woodruff's ob- 

 servation (1932) among others which showed that 5071 genera- 

 tions produced asexually from a single individual of Paramecium 



