88 MR. W. BATESON OJS" COLOUR-HEREDITY [May 26, 



calling for elucidation is the distinction between the black-and- 

 white of the original waltzers and the black-and-white of sub- 

 sequent generations. F^ from albino and the waltzers was the 

 atavistic grey, but there is no indication that the subsequent 

 heterozygotes between blw. and albino were grey ; or more 

 strictly there is a gi'eat deal of evidence that they were usually 

 blw. The suggestion also that the atavistic colour was due to the 

 union of the waltzing and non-waltzing charactei- seems to be 

 plainly excluded, because even normal albinos in later generations 

 proved to be heterozygotes of waltzing and non- waltzing gametes. 

 At present, therefore, we cannot declare what was the difference 

 between the original pure gametes which caused the reversion 

 when they were united. 



Lastly, thei-e is a difficidty, perhaps the most serious of all, in 

 the result of the union of albino x self-grey (19. p. 328, 2nd pair, 

 both parents being in Fj) which gave 13 grey, 3 grey-and- white. 

 I see at present no suggestion as to the gametic production of the 

 grey parent in this case which can be made with any probability, 

 consistently with the other facts. Possibly the diversity of 

 gametes lay with the albino. 



I now pass to an examination of the evidence of Darbishire, 

 who crossed ordinary albino mice with waltzers. The waltzers 

 used were " pale fawn "-and- white with j*ji7?.^- eyes, thus outwardly 

 corresponding somewhat with one of the breeds of rabbits called 

 " Himalayan." The nature of the pigmentation described as 

 " fawn " is not specified ; but from the results, and especially 

 from the distinction drawn by the author between "fawn," 

 " fawn-yellow," and " yellow," there can be little doubt that the 

 fawn was composed of both yellow pigment and a dark pigment, 

 probably black. Twenty-nine pau-s were used in the pi-oduction 

 of F^. The offspring oif 23 of these pairs, 120 individuals, had 

 grey colour. All except one had more or less white or whitish, 

 differing in extent. Some had more white than the waltzers, 

 while in others the whitish colour only appeared on the belly. 

 The pure albinos gave on the whole more fully coloured, the 

 extracted albinos less fully coloured heterozygotes. The tint of 

 the grey is further classified into "pale wild colour" and " dark 

 mid colour," both being stated to be such as occur in muscidus. 

 Full details as to distribution are given [q. v.). 

 ^ -Of the remaining six pairs, four gave one or more mice with 

 the colour-patches black (with grey brethren in three families) 

 as follows : — 



Pair. ^, Patches. 



Grey. Blaclc. 



XXVII 1 



LXXYII 1 3 



LXXYIII 4 3 



LXXXY J 2 



11 "9 



