The Theory of Natural Selection. 267 



other parts of that species may survive for any number 

 of ages as they originally were. In the one case there 

 is a ladder-like transmutation of species in time ; in 

 the other case a possibly tree-like multiplication of 

 species in space. But whether the evolution of spe- 

 cies be thus serial in time or divergent in space, the 

 object of natural selection, so to speak, is in either 

 case the same namely, that of preserving all types 

 which prove best suited to the conditions of their 

 existence. 



Once more, the term " struggle for existence " must 

 be understood to comprehend, not only a competition 

 for life among contemporary individuals of the same 

 species, but likewise a struggle by all such individuals 

 taken collectively for the continuance of their own 

 specific type. Thus, on the one hand, while there is 

 a perpetual civil war being waged between members 

 of the same species, on the other hand there is a 

 foreign war being waged by the species as a whole 

 against its world as a whole. Hence it follows that 

 natural selection does not secure survival of the fittest 

 as regards individuals only, but also survival of the 

 fittest as regards types. This is a most important 

 point to remember, because, as a general rule, these 

 two different causes produce exactly opposite effects. 

 Success in the civil war, where each is fighting against 

 all, is determined by individiial fitness and self-reliance. 

 But success in the foreign war is determined by what 

 may be termed tribal fitness and mutual dependence. 

 For example, among social insects the struggle for 

 existence is quite as great between different tribes or 

 communities, as it is between different individuals of 



