78 THE INHERITANCE OF COLOR IN MICE. 



RESTRICTED SERIES. 



All animals in this series, that is to say, all yellow animals, are of the zygotic formula Rr. 

 The combination RR, if formed, fails to develop. 



(a) Dark-eyed intense series. 



This series consists of four types of yellows : 



XVII. Black-eyed Yellow Carrying Agouti, YBrBDPAR (Fig. 20). 

 XVIII. Black-eyed Yellow Without Agouti, YBrBDPR (Fig. 17). 

 XIX. Brown-eyed Yellow Carrying Agouti, YBrDPAR. 

 XX. Brown-eyed Yellow Without Agouti, YBrDPR (Fig. 18). 



Types XVII and XVII are similar in appearance, and are indistinguishable save by breed- 

 ing tests. Types XIX and XX also are only to be distinguished from each other by 

 suitable test matings. 



(b) Pink-eyed intense series. 



This series consists of four types of yellow which are indistinguishable in external appearance: 



XXI. Pink-eyed Yellow Carrying Black Agouti, YBrBDpAR. 

 XXII. Pink-eyed Yellow Carrying Black, YBrBDpR. 



XXIII. Pink-eyed Yellow Carrying Brown Agouti, YBrDpAR. 



XXIV. Pink-eyed Yellow Carrying Brown, YBrDpR. 



Test matings are necessary before these forms can be distinguished from each other. 



(c) Dark-eyed dilute series. 

 In this series also there are four tj^pes: 



XXV. Black-eyed Dilute Yellow Carrying Agouti, YBrBdPAR. 

 XXVI. Black-eyed Dilute Yellow Without Agouti, YBrBdPR. 



XXVII. Brown-eyed Dilute Yellow Carrying Agouti, YBrdPAR. 

 XXVIII. Brown-eyed Dilute Yellow Without Agouti, YBrdPR (Fig. 19). 



In this series types XXV and XXVI are distinguishable from types XXVII and XXVIII 



by a careful examination of the eyes. Such a test, however, is not certain enough to 



be considered final, and a breeding test forms the only sure basis for a permanent 



classification. 



(rf) Pink-eyed dilute series. 



As in the pink-eyed intense series the four forms of this series are indistinguishable save by 

 breeding tests. This is because of the fact that the total amount of pigment in the 

 eye is so small that it is impossible to determine whether it is brown or black by any- 

 thing short of a microscopic examination. The gametic formulae follow: 



XXIX. Pink-eyed Dilute Yellow Carrying Black Agouti, YBrBdpAR. 

 XXX. Pink-eyed Dilute Yellow Carrying Black, YBrBdpR. 

 XXXI. Pink-eyed Dilute Yellow Carrying Brown Agouti, YBrdpAR. 

 XXXII. Pink-eyed Dilute Yellow Carrying Brown, YBrdpR. 



Each of these series may now be considered separately. 



Up to a certain point there were no pink-eyed or dilute mice, yellow or non-yellow in my 

 stock. All the yellows were therefore intense dark-eyed yellows and would group them- 

 selves under one of the first four types (XVII, XVIII, XIX, or XX). To test them a 

 cross with any type of brown animal lacking the agouti factor would suffice. 



A list of such crosses follows. Yellows which proved to be of type XVII are included in the 

 following table: 



