Morgan, T. H. The influence of heredity and of environment in determining 



the coatcolors in mice. Annals N. Y. Acad, of Soc. 1911. 



One of the most important features of this paper is a description of 

 a wild sport of Mus muscu/ns, and the behaviour of the genetic factor which 

 distinguished this sport from other house-mice in inheritance. Tliesc wild 

 sports differed from other mice in the colour onl}-, the belly being white 

 instead of gray, and the colour of the back being darker. From the 

 description of this wild sport, I believe it differs from the other mice, in 

 the possession of a genetic factor which has been studied by Pi ate and 

 by me in house-mice and by Miss Sollas in cavies In my work on these 

 factors I have called it H. I found that in respect to this factor H, the 

 wild .l/.Y.v miisciihn in Holland as well as around Verrieres are of two kinds, 

 such as have it, and such as lack it. Platk and I both found that 

 whenever this factor was absent from a coloured mouse, the colour of the 

 coat was much fader than that of the animals containing it. Black mice 

 there fore witliout H are fade black, which means that the coat, especially 

 of the young mice is not deep, glossy black, but brownish, lustreless. This 

 colour, it seems to me would be the colour of the young mice observed 

 by Morgan, as born from a mating of a black and white waltzer and a 

 chocolate animal. I venture to think that the chocolate used was a fade 

 chocolate, and the black and white a fade one also. For it is quite 

 possible that a fade black animal, if its colour is limited to patches, con- 

 trasting on an otherwisely white coat, looks as if the coat contains this 

 factor H. Thus, nobody would have any difficulty in distinguishing black 

 and chocolate mice, when they are wholly coloure, but a chocolate spotted 

 mouse, that is, a white animal with a few small spots of chocolate may 

 on first ins])ection pass for a black and white, as by contrast the colour 

 looks much darker. 



I believe it will be easy to verify, whether the factor which distin- 

 guished Ms white-bellied and gray-beUied housemice, is my factor H, for 

 in that case, the young agoutis which Morgan bred from a cross of choco- 

 late y whitebellied agouti, should in the Fo generation give two kinds of 

 chocolate, such having H, dark, rich chocolatebrown with black eyes, and 

 such without H with a much paler coat, and probably with eyes which 

 would look ruby under a certain light. 



The original sports studied by M, proved to be heterozygous for the 

 factor in question. 



It seems that Morgan has difficulty in distinguishing agouti and 

 cinnamon agouti mice, which differ in the possession or non-possession of 

 the factor which also makes the difference between chocolate and black 

 animals. I do not think any of the other authors on the subject has ever 

 had this difficulty. M. in his ratios always adds agoutis and cinnamons 

 together. It is difficult to see what M. means by the name "golden 

 agouti", the fancier's name for the ordinary agouti color of Mns musailiis, 

 ABCDEFGH in my formulae. 



To test the hypothesis, offered in a former paper, namely, that segre- 

 gation might be a dynamic function of divisions in the germcell. which 

 would imply the impurity of gametes, in the sense that possibly the 

 extracted recessive may under certain circumstances give rise to a domi- 

 nant, Mori. AN made the following experiment. He mated an extracted 

 dominant agouti mouse (an AAHHCCDUEEFFGGHH) from (AaBBCCDD 

 EEFFGGHH) parents to black (AABBCCDDEEFFggHH) getting agoutis 



