W. F. R. AVkldon 297 



Colon r ; the inilividuals j)n)(iiicc(l Crom the 11111011 of such (rnmctcs sliould nii 

 Mendcl's view bo like iiidividuals of the pure waltziiig race, 011 Mr l3ateHoii's vicw 

 they shoiild be "not like but identical with " their pure-bred waltziiig grand- 

 parent, both in eye-colour and in coat-colour (IT. p. 12). Now Mr Darbishiro 

 has pointed out (Biometrika, Vol. II, Part 2, pp. 167 and 1G8) that the mico, 

 which Mr ßateson calls of Constitution G'G' niay e.xhibit a blue-grey colour which 

 breedens call " lilac," unknown in the purc-bred waltzing race (at least in the 

 recent ancestry of the mico used) aud equally unknown in hybrids of the first 

 generatiou, wiiich Mr Batcson calls GG'. At the tiino of writing, there are LS 

 rnice of the group G'G\ all "pink-oyed, with seine colour in the coat," and of tliese 

 no less than six are either wliiill\- or in part lilac. 



The coat-colour of the 36 mice GG' is also variable, as is that of those mice 

 (which Mr Bateson regards as having the same Constitution) produced by crossing 

 hybrids of the first genoration with albinos. The variability of coat-colour, un- 

 aecompanied by a resolution of the allelomorpli, is as great an obstacle to 

 Mr Bateson's interpretation in this case as in tho case of the first cross. 



Here, as in so many other cases, a result in superficial agreement with those 

 observed by Mendel can ouly be obtained by devising a series of categories so 

 vaguely defined that they convey wholly inadequate information; and with a little 

 skill such categories niay be found to fit almost any series of results. Just as on 

 a former occasion Mr Bateson has used the category " hairy " to imply identity of 

 character between leaves in which the niimber of hairs per Square centimetre may 

 be aiiything from a dozen to over a thousand, so he here assumes that the con- 

 ditions of eqnality, suggested when he asserts that 18 mice are of identical 

 Constitution G'G', are satisfied when he has shown that they all have " pink eyes 

 " and some colour in the coat." Such a categoiy would include a pink-eyed mouse 

 with green für and a purple tail ; and he makes it in fact include " lilac " and 

 yellow. 



Surely we want some better demonstration of the "identity" between pure 

 dominants aud their parents than this sort of category can give, before the "great 

 " fact of gametic purity " can serve as a foundation for the huge superstructure of 

 hypothesis built ujion it ! 



When it is pointed out to Mr Bateson that he cannot legitimately class yellow, 

 lilac, aud black in a single colour category, he abandons his formula of March 19 

 and puts forward a new set of hypotheses (Nature, No. 1747, April 23, p. 585). 

 He uow explains the variability aniong Mr Darbishire's first crosses as due to 

 gametic impurity in one or both of the races crossod. Now, apart frora the 

 difficulty of regarding a " pure i'ecessive " albino as impure in the Mendelian sense, 

 let US see whether the new statemeut fits the observed behaviour of the "pui'e" 

 waltzing mice. The waltzing mice used by Mr Darbishire are chiefly descended 

 from abuut 80 mice, 40 of each sex, bought by me some time ago, and paired 

 at random under my direction. Now if we suppose these mice to have been 

 impure in Mr Bateson's sense, that is, if we suppose them to have produced 



Biometrika 11 38 



