406 ME. G. J. KOMANES ON PHYSIOLOGICAL SELECTION. 



POSTSCEIPT. 



In the discussion whicli followed tlie reading of this paper, 

 certain difficulties or objections were put forward by one or two 

 of the more eminent naturalists who happened to be present. 

 These I answered verbally ; but, inasmuch as they may also 

 occur to readers of the paper, I will here briefly consider 

 those among them which do not appear to have been sufficiently 

 anticipated in the course of the preceding pages. 



!First, it was objected that breeding in and in has a tendency 

 to deteriorate off'spring, and therefore that physiological selec- 

 tion, by limiting the area of breeding, would yield a variety less 

 able than its parent form to compete successfully in the struggle 

 for existence. This objection, however, would only be of any 

 force where an exceedingly small number of individuals are con- 

 cerned ; and even then, I think, it may be neglected, seeing that 

 in the course of a very few generations consanguinity becomes 

 diluted in so rapid a ratio, even in the case of species which pro- 

 duce but few at a birth. On this point I may refer to the 

 ' Origin of Species,' pp. 72, 238, and 252, to show that even 

 Mr. Darwin (who more than any other writer has insisted on 

 the benefit arising from cross-fertilization) disregards the effects 

 of interbreeding, where more than a very few individuals are 

 concerned. 



Next, it was objected that it could be of no use to a varietal 

 type that it should be separated from the parental. I have, 

 however, argued that the use would be three-fold : 1st, the variety 

 would thus be started on an independent course of history ; 

 2ud, it would therefore be able " to seize on many and widely 

 diversified places in the economy of nature ; " and, 3rd, it would 

 derive the advantage that breeders find in keeping their strains 

 from intercrossing. But, over and above all this, the theory of 

 physiological selection does not require that the separation in 

 question should be of any use ; and, therefore, this objection to 

 the theory falls to the ground as irrelevant. So long as there is 

 no actual detriment arising to the variety on account of its being 

 separated from the parent, any ideas derived from the theory 

 of natural selection are plainly without bearing upon the 

 subject. 



Lastly, it was in effect suggested that the theory of physio- 

 logical selection is merely the re-statement of a fact. For,. 



