ME. G. J. EOMANES ON PHYSIOLOGICAL SELECTION. 38^ 



may be f urnislied by any one who accepts the theory of physio- 

 logical selection. Tor, upon this theory, it is quite intelligible 

 that when a varietal form is differentiated from its parent form 

 by the bar of sterility, any little meaningless peculiarities of 

 structure or of instinct should at first be allowed to arise, and 

 that they should then be allowed to perpetuate themselves by 

 heredity, until — not being conserved by natural selection — they 

 should be again eliminated as so much surplusage in the struggle 

 for existence, whether by the economy of growth or by indepen- 

 dent variation when undirected by natural selection. A greater 

 or less time would in different cases be required to effect this 

 reduction ; aud thus we can understand how it is that any use- 

 less structures which do not impose much tax upon the organism 

 occasionally persist even into genera, but rarely into families, or 

 higher taxouomic divisions. 



This appears to me much the most probable view, not merely 

 on a priori grounds, but also for the following reasons. I have 

 just said that if apparently useless structures (whether these be 

 new structures or modifications of old ones, slight changes of 

 form, colour, and so forth) are thus to be regarded as really 

 useless, or as meaningless variations not yet eliminated by natural 

 selection or other agencies, — I have said that, if this is so, these 

 apparently useless structures must be of a kind which do not 

 impose much tax upon the organism. Now I have applied this 

 test, and I find it is almost an invariable rule (both in plants 

 and animals) that apparently useless structures are structures 

 of this kind. Either on account of their small size or of their 

 organically inexpensive material, they are structures which do 

 not impose any such physiological tax upon the organism as 

 should lead us to expect their speedy removal. But surely 

 there can be no imaginable association between utility as 

 disguised and smallness of size, or inexpensiveness of material. 

 "Whereas, no less surely, there is a most obvious connection 

 between these things and a real inutility. Thus, it is only a 

 blind prepossession in favour of survival of the fittest as in 

 all cases the originating cause of species that can lead to so 

 irrational an assumption as that of universal utility. 



Again, even apart from all the above considerations, the truth 

 of this remark may be well exemplified within the limits of Mr. 

 Darwin's own writings ; for Mr. Darwin is here, as usual, his own 

 best critic. He says, " In the earlier editions of this work I 



