80 SEX 



itself indefinitely, under favourable environ- 

 mental conditions, without recourse to con- 

 jugation." His experiments indicate that 

 senescence and the need of fertilisation are 

 not primary attributes of living matter. 



Without surrendering the idea that con- 

 jugation, though not necessitated by a long 

 succession of asexual reproductions, may 

 serve to re-invigorate the protoplasm when 

 the environment is not perfect, we are led to 

 look about for some other part that conjuga- 

 tion may play in the life of the race. The 

 suggestion has been made that it enables the 

 organism to withstand changed environmental 

 conditions a view which may be readily 

 combined with the idea of re-invigoration. 

 It has been suggested, also, that it may be 

 a process by which the average character 

 of the species is sustained, disadvantageous 

 peculiarities of any individual Protozoon 

 being counteracted by other characters in 

 the unrelated neighbour with which it con- 

 jugates. Or it may be that the process of 

 conjugation is a source of variation by bringing 

 about new combinations among the essential 

 substances of the two conjugates. The recent 

 work of Jennings supports the view that the 

 significance of conjugation lies in securing 

 biparental inheritance, which often implies 

 variation. When the conditions of life are 

 untoward, conjugation is apt to occur, and 

 it may be followed by new combinations of 

 qualities, some of which are suited to the 

 altered conditions of life. Conjugation pro- 

 motes variations, and some of these pay by 

 securing survival. 



