EFFECT OF CONJUGATION 377 



called an adaptation. Its result is to insure that in all organisms 

 that develop there shall be inheritance from two parents, not 

 from one. In the work on artificial parthenogenesis these two 

 functions have been separated experimentally; the initiation of 

 development takes place alone. 



Now, in endeavoring to understand conjugation, attention has 

 been given hitherto almost exclusively to the first of these two 

 functions. It was held that the function of conjugation must 

 be to make possible life and development where it was otherwise 

 impossible, just as fertilization arouses the egg to further life 

 and development. But it turns out that in the infusoria con- 

 jugation, instead of having this one of the two functions of fer- 

 tilization, has the other. The two functions are in the infusorian 

 separated, just as they are in artificial parthenogenesis, but it is 

 the second, not the first, that we have before us. Conjugation 

 is not necessary in order that life and reproduction shall continue; 

 they continue without it. There is no evidence that conjugation 

 in the infusoria increases the reproductive power, or rejuvenates 

 the organism physiologically in any way. 



But the life which thus continues is uniform and unchanging. 

 To give biparental inheritance, with varying mixtures of the 

 characteristics of the two parents; to produce these new combina- 

 tions in great varietj^, conjugation is necessary. And when this 

 happens under such conditions that the original combinations 

 were not adapted to survival,, then some of the new combinations 

 produced often are adapted to the conditions; conjugation then 

 results in a survival of an organism that would have been com- 

 pletely destroyed without it. It is most interesting in this 

 connection to observe that conjugation is usually induced by an 

 unfavorable change of conditions, a change of such a nature that 

 the organisms begin to decline. Thereupon conjugation occurs, 

 so that new combinations are produced, adapted to varied con- 

 ditions, some of which may survive. 



Thus the whole series of investigations on vegetative reproduc- 

 tion and on conjugation leads to a unified result, and one that is 

 in consonance with what we observe in higher animals. 



