AGE, DEATH AND CONJUGATION 571 



conjugation, but to the fact that he used a wild specimen, which had 

 not been living under unadapted conditions. He apparently used the 

 progeny of this wild individual for the remainder of his study. Now, 

 the results I have just described show that if he had not allowed this 

 animal to conjugate, it would have gone on multiplying just as well. 

 Conjugation had nothing to do with the result, the fact that the speci- 

 men came from natural conditions is what counted. 



Miss Cull's evidence for rejuvehescence consisted in showing that a 

 considerable part of those that had conjugated continued thereafter to 

 multiply. In the absence of the control experiment, she did not dis- 

 cover that they continue equally if they have not conjugated. There is 

 then in this no evidence for a rejuvenating effect of conjugation. 



2. To return to my own investigations, the second important result 

 was to show that the specimens which have been allowed to conjugate 

 multiply much less rapidly than those which have not conjugated. 

 The difference is very marked, and showed itself in every experiment 

 of a great number. The multiplication is slower, in those that have 

 conjugated, for a month or two after conjugation. 



This result seems surprising, in view of the widespread impression 

 that multiplication becomes slower and slower, when the animals are 

 kept without conjugation, and that the function of conjugation is to 

 raise the vitality to the pitch where multiplication may continue at the 

 normal rate. It is therefore interesting to note that those sterling 

 investigators, Maupas and Eichard Hertwig, knew well that conjugation 

 does not increase the rapidity of multiplication. Maupas emjDhasizes 

 and insists upon this fact again and again, at much length, in opposi- 

 tion to the prevailing view that conjugation increases the power of 

 multiplication. AVhat Maupas held was that conjugation saves the 

 animals from death, though without increasing their reproductive 

 powers. Eichard Hertwig observed, correctly, that conjugation actu- 

 ally decreases the rate of multiplication. 



3. A third result of comparing those that have conjugated with those 

 that have not is that many more of the former die or are abnormal than 

 of the latter. In a specially favorable experiment, out of 61 conjugants, 

 eleven lines had died out completely in 33 days, while of 59 lines that 

 had not conjugated, but were otherwise similar, none had died in the 

 same period. 



4. Usually a considerable number of the conjugants never divide 

 after conjugation, while all of those that have not conjugated continue 

 dividing. 



5. There is much greater variation among the progeny of those that 

 have conjugated than among those that have not. This greater varia- 

 tion shows itself (1) in the rate of multiplication; (3) in dimensions. 

 If we determine the coefficients of variation, we find these much greater 

 in the progeny of those that have been allowed to conjugate. 



