A. I). DARnisiiiRE 173 



Postsaipt, added Feh. 12, l!)0:i 



The iiiiri', ivsulting i'nim :i first cross between albinos and pink-eyed vvaltzing 

 mice, are iiow 203, all tlie iiulividiials having dark eyos, while noiie have wholly 

 white für, aud none waltz. lu tlio secoiid gencratiou, therc arc CG mice produced 

 by pairing hybrids ; of these 13 are pink-eyed albinos, and 17 have pink eyes and 

 coats more or less coloiired. In tho same generation there are 205 individnals 

 produccd by crossing albinos with hybrids ; of these 111 are albinos, thc remainder 

 having dark eyes and some colour in the coat. 



The proportions of albinos and of individnals not albino are not in disagree- 

 ment with Mendels rcsults, bat the exhibition of these results in Mendelian form 

 depends on the adoption of a quite artificial category of coat-colours ; for albinisni 

 inclndes only pure whiteness of coat, while coloured coats include the whole ränge 

 of conditions froni white with sniall patches of pale yellow to dark " wild colour " 

 or black. 



The inheritance of ey'e-colour is not in accordance with Mendels resnlts. For 

 since pink eyes occur in particoloured mice, the possession of pink eyes must on 

 Mendel's view depend on a separate embryonic element from that which deter- 

 mines coat-colour. Pink eyes are however not "dominant," since the two pink- 

 eyed parents of the tirst generation always produce dark-eyed young. For the 

 same reason pink eyes are not " recessive." Yct although pink eyes disappear in 

 the first generation (the result of crossing two pink-eyed parents) they reappear 

 in the secoud ; but a correlatiou is then established between coat-colour and eye- 

 colour which is strong in the offspring of hybrids paired together, and at present 

 perfect in the offspring of liybrids and albinos. The behaviour of eye-colour is 

 thus in every respect discordant with Mendels resnlts. 



