THE SPECIES 243 



this dividing is useful for the individual and not for the 

 species, if the offspring continue alike throughout. On the 

 other hand, sexual reproduction is there essentially in the 

 interests of the species, because it ensures the crossing of 

 the genes. 



Moreover, the extravagant production of young is solely 

 in the interests of the species ; this perpetually gives the 

 species the chance to make use to the full of all favourable 

 opportunities, and to come through bad times without essen- 

 tial loss. If the genotype of the species is preserved by a few 

 survivors, that is sufficient to secure its continued existence. 



The difficulty of picturing the species as consisting of 

 numerous individual organisms and yet being an entire organ- 

 ism itself, depends only on the fact that the separate creatures 

 do not perform their actions at the same rate or at the same 

 place. Let us imagine the species as, for instance, a large 

 shoal of fishes hunting a great quantity of pteropods, and 

 followed in their turn by a number of sharks. We at once 

 get the impression of a huge organism, pursuing and pursued, 

 which now spreads out, now draws together, here becomes 

 larger, there becomes smaller, but fundamentally remains the 

 same throughout. At one point speed, at another slowness, 

 at one point dark coloration, at another light, here sharp 

 sight, and there a keen sense of smell, act for the preservation 

 of the whole. So long as the whole retains all these properties, 

 it will continue its existence unchanged, although that essen- 

 tially consists of perpetual flight and pursuit. 



I think there can be no doubt that every species represents 

 really an independent organism with a character of its own 

 but endowed with tremendous longevity. 



K. 



