Sara White Cull 



end of the month, of the sixty-five pairs then represented by living 

 cells, in twenty-seven pairs, or forty-one per cent, one of the excon- 

 jugants only or the offspring from it were alive; in fifteen pairs, or 

 twenty-three per cent, the progeny of one exconjugant was three 

 times as large as that of the other; in six pairs, the descendants of 

 the one were twice as numerous as those of the other organism; 

 and in only five cases had both conjugants given rise to the same 

 number of offspring. The twelve remaining pairs showed a wide 

 disparity in the number of paramecia produced by any two con- 

 jugants. The following table shows these results in summarized 

 form : 



* Exclusive of cases where the progeny of one exconjugant had died. 



It may be broadly stated that of the sixty-five pairs which I have 

 observed one conjugant either died or left a weak strain in which 

 the descendants were half as numerous and much less vigorous 

 than those of the stronger exconjugant. This striking difference 

 in the restored vitality of the conjugants and their descendants 

 gives strong grounds for the belief that conjugation as seen among 

 these infusoria is really incipient fertilization as seen among the 

 higher forms of life. Here we have indications that one gamete 

 gives up its vitality to and loses its individuality in the other just 

 as the spermatozoon loses its identity in the egg where its presence 

 forms a stimulus to development analogous to the rajeunissement 

 and greater activity in cell division which follows conjugation. 

 There is little reason to doubt that a physiological and perhaps a 



