AUTHOR S ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, NOVEMBER 7 



UROLEPTUS MOBILIS ENGELM. 



IV. EFFECT OF CUTTING DURING CONJUGATION 

 GARY N. CALKINS 



TEN FIGURES 



In the second of these studies^ it was demonstrated that con- 

 jugation brings about a renewal of vitality in protoplasm in 

 which the vital activities have become reduced, or even nearly- 

 exhausted, by physiological usury. It was also shown that a 

 similar renewal of vitality follows the reorganization which takes 

 place asexually during encystment, indicating, as Woodruff and 

 Erdmann have shown for Paramecium, that nuclear fusion or 

 fertilization in Uroleptus is unnecessary in the phenomenon of 

 rejuvenescence. 



A bit of protoplasm possessing only sufficient vitality to enable 

 it to divide once in forty days unites in conjugation with a 

 similarly weakened and closely related bit of protoplasm; the 

 ex-conjugant from this pairing possesses a restored vitality which 

 enables it to divide at the rate of seventy-two times in the 

 same forty days. As a unit mass of protoplasm or individually, 

 the ex-conjugant is the same as before conjugation, but some- 

 thing has occurred in its organic make-up to bring about the 

 change. In the first of these studies^ the cytology of conjuga- 

 tion was fully worked out, and it was found that, as with ciliates 

 generally, the only recognizable physical changes have to do 

 with the nuclear complex. Not only are all of the eight macro- 

 nuclei absorbed in the cytoplasm but in addition, not less than 

 seven-eighths of the micronuclear material is likewise absorbed. 



A similar absorption of nuclear substance characterizes the 

 process of asexual reorganization accompanjdng encystment, and 



1 Jour. Exp. Zool., vol. 29, 1919. 



2 Jour. Exp. Zool., vol. 27, 1919. 



449 



