28 SEX 



ebbs. The conjugation may be dangerous for 

 the individual, it is a loss of time so far as 

 immediate multiplication is concerned, but it 

 is necessary to keep up the vigour of the stock. 

 Without it, the Protozoa, which are otherwise 

 practically exempt from natural death, must 

 die. Conjugation is the necessary condition of 

 their eternal youth. The experiments made 

 by Maupas were conducted with great care, 

 and they formed (along with other facts) 

 the basis for what is sometimes called the 

 " dynamic " theory of conjugation that it 

 is " a satisfying of an inherent periodic physio- 

 logical need of living matter, resulting in a 

 renewal of the vigour of the cell." But 

 subsequent experiments have given a some- 

 what new complexion to the facts. It has 

 been shown, for instance, that Infusorians 

 are extraordinarily sensitive to their own 

 waste products, and it has been suggested 

 that the degeneration described by Maupas 

 was due to self-poisoning rather than to the 

 absence of conjugation. 



Some subsequent investigators have watched 

 hundreds of successive asexual generations 

 without seeing the slightest trace of senile 

 degeneration. Calkins has cultivated the 

 slipper animalcule (Paramoecium) for over 

 six hundred generations without conjugation, 

 by giving beef extract when degeneration 

 threatened to set in. The same warding off 

 of evil has been obtained with the same 

 Infusorian by stimulating with infinitesimal 

 quantities of alcohol, strychnine and the like. 

 The trend of recent work has been to suggest 

 that in a perfect environment conjugation 



