EFFECT OF CONJUGATION 373 



vigor was due to the fact that it had been living under favorable 

 conditions, not to conjugation. 



There is absolutely nothing in this experiment to demonstrate 

 that a partially exhausted race is rejuvenated by conjugation. 

 A real test would be the following: Two unrelated lines should be 

 allowed to multiply till both become depressed. Then they should 

 be allowed to conjugate, to determine whether the conjugation 

 remedies the depression. It will manifestly not do, in testing 

 the question whether conjugation remedies depression, to take a 

 vigorous, undepressed specimen as one member of the pair. 

 According to the cyclical theories, all lines of propagation become 

 depressed after a series of vegetative reproductions, so that if 

 conjugation is to maintain the race, it must be effective when it 

 occurs between two lines, both of which are depressed. 



Now, as we have briefly mentioned above, Maupas performed 

 this crucial experiment. He kept lines of propagation of Stylony- 

 chia of diverse origin till they became depressed, then allowed 

 them to conjugate one with another. This fact is briefly set 

 forth on page 409 of his paper of 1889. Such cross-conjugation of 

 two diverse lines did not result in rejuvenescence; the animals died 

 just as happened when the two members of a pair came from the 

 same parents. Speaking of sterile conjugations, Maupas says, 

 "Elles s'effectuent, en effet, aussi bien entre individus apparte- 

 nant a un meme cycle ou proches parents, qu'entre individus 

 etranges Tun a I'autre et provenant de cycles differents" ('89, 

 p. 409). 



Anyone who goes critically through the 480 pages of Maupas' 

 two great papers for the purpose of finding out what evidence 

 there is that conjugation rejuvenates, will, I believe, be forced, as 

 I have been, to realize that they contain no evidence for this 

 whatever, although they do contain evidence against it. Maupas' 

 conclusion was evidently due to the supposed theoretical neces- 

 sity for something to remedy the degeneration induced by long 

 vegetative reproduction under the conditions of his experiments. 

 All that his experiments show is that long continued propagation under 

 the given conditions results in injury to the stock — and this equally 

 whether there is or is not conjugation within the stocks, or between 



