238 APPENDIX II INTENSIVE SEGREGATION. 



few that seem to be "mere tricks" or "habits without use to the ani- 

 mals." Mr. Romanes, referring to these cases, offers the following 

 explanation on page 275 of the same work (I quote from the New 

 York edition, Appleton & Co., 1884) : 



We have seen abundant evidence that non-adaptive habits occur in individuals, 



and may be inherited in the race. Therefore, if from play, affection, curiosity, or 



even mere caprice, the animal should perform any useless kind of action habitually 



and if this habit were to become hereditary in the similarly constituted 



progeny, we should have a trivial or useless instinct. 



As an example of a strongly inherited non-adaptive instinct in a 

 wild creature may be mentioned the cackling of the wild hen of India 

 after having laid an egg. This habit is referred to by Darwin as one that 

 may be slightly detrimental ; but all that is necessary to put it beyond 

 the developing influence of natural selection is that it should fail of 

 bringing advantage to the species ; and that it is of no advantage will, 

 I think, be generally admitted. If, then, species differ in regard to 

 instincts that are non-advantageous, they are liable to present non- 

 advantageous differences in form and color, resulting either from the 

 same causes that have produced the divergent instincts, or from 

 divergent forms of environal, sexual, and social selection produced by 

 these instincts ; it will, however, be found that segregate intergenera- 

 tion is the necessary condition on which the divergence of innate 

 characters depends. 



In the present paper and in other places I have mentioned cases, 

 representative of multitudes of others, in which there is divergence 

 between two varieties or species occupying different districts, but 

 surrounded by the same environment. In such cases the differ- 

 ences presented by the separate forms, and the divergence by which 

 the differences have been produced, can not be regarded as advan- 

 tageous ; for if the forms should exchange districts, the environment 

 being the same, no disadvantage would be experienced; and this is 

 equally true whether the differences relate to industrial adaptations 

 or to adaptations between the sexual instincts and the secondary 

 sexual characters of the group, or to characters that are absolutely 

 non-utilitarian. 



Mr. Wallace says that in my previous paper he looks in vain for 

 any proof that cumulative segregation produces cumulative diver- 

 gence ; but at the same time he claims that the segregation of which I 

 speak, and which I have illustrated by a supposed case in the breeding 

 of pigeons, is a form of selection which he calls "selection by separa- 

 tion." Adopting his phrase for the moment, I understand that he 

 fully admits that in domestication "selection by separation" will 



