REJUVENESCENCE AS THE RESULT OF 

 CONJUGATION 



SARA WHITE CULL 



Thirty years ago Biitschli proposed the view, since confirmed 

 by Maupas and others, that the life histories of infusoria run in 

 cycles, and that a period characterized by binary fission is fol- 

 lowed by another in which conjugation takes place; this latter 

 process resulting in a thorough reorganization of the excon- 

 jugants and a Verjungiingov rejuvenescence, which shows itself in 

 a higher rate of cell division and, generally speaking, in renewed 

 life activities. If conjugation does not take place nor an equivalent 

 stimulus be given the organisms they will eventually die of 

 what has been termed "protoplasmic old age." 



Hitherto it has been supposed that both cells in conjugation 

 were benefited by the process, a mutual fertilization taking place; 

 but in a series of experiments made by Calkins on Paramecium 

 caudatum, the fact was noted that when both exconjugants live, 

 in some cases one is far more vigorous than the other, as demon- 

 strated by the greater number of offspring in one case than in the 

 other. ^ Dr. Calkins suggested that I should examine this point 

 and carry out some other observations that he had already made. 

 The work was done in the zoological laboratory of Columbia 

 University in the fall and winter of 1905-06. 



Biitschli has pointed out the striking analogy which exists be- 

 tween conjugation and fertilization as it is seen among higher 

 organisms and among those protozoa which show sexual dimorph- 

 ism. In many of these forms such as the peritrichous ciliates or 

 the coccidiida, there is a marked sex-difi^erentiation in the size 

 and activity of the gametes. Here in fertilization, a more or less 

 passive individual of normal or more than normal size, a macro- 



' Studies on the Life History of Protozoa. I Arch. f. Entwk., Bd. xv, i 02. 

 The Journal of Experimental Zoology, vol. iv, no. i. 



