2 1 6 Struggle for Existence and Rivalry 



tion has come to rest more and more upon the second and 

 third sorts of struggle (2 and 3), and less on the Malthu- 

 sian conception (i). Experimental studies which support 

 the selection view {eg., Weldon on Crabs, Poulton on Chry- 

 salides) ^ show the ehminative effect of the environment, 

 and the preying of some animals upon others, rather than 

 direct competition inter se, among individuals of the same 

 species, for food or other necessities of life. It is these 

 forms of the struggle, too, that we find nature especially 

 providing to meet, through adaptive contrivances such as 

 concealing and warning colours, mimicry, offensive and 

 defensive organs — teeth, claws, horns, etc., — with comba- 

 tive, aggressive, and predatory instincts, on the one hand, 

 and by high plasticity and intelligence on the other. 



The result common to all the sorts of struggle for existence, 

 however, is the survival of an adequate number of the fit- 

 test individuals ; and this justifies the use of the term in the 

 theory of evolution to cover so wide a variety of instances. 



Darwin, on reading Malthus' book On Population, con- 

 ceived the idea that overpopulation would be a universal 

 fact in organic nature were there no process by which the 

 numbers were constantly reduced. He was thus led to 

 lay stress on the struggle for existence, and the eHmina- 

 tion of those individuals which were unsuccessful. Com- 

 bining this conception of elimination in the struggle with 

 that of variation, he reached the hypothesis of natural 

 selection. A similar relation to Malthus is also true of 

 Wallace (see Poulton, Charles Dariuin, pp. ^S f.)2 In this 

 case the struggle arises from common wants, combined with 



1 Weldon, Proc. Roy. Soc. London, LVII., pp. 360 ff., 379 ff.; Poulton, 

 Proc. Brit. Ass., Bristol Meeting, 1898. 

 * See also p. 46 of the same work. 



