Experimejital Hybridiziiig 91 



some of the descendants, if these albinos are crossed with colored 

 types. Thus if an albino ^G be crossed with an albino AB, 

 the albino offspring will be AGAB. Its germ-cells will separate 

 into AG and AB, but these are albinos. If, on the other hand, 

 a black mouse, CB, be mated with an albino A Y, containing 

 yellow as a latent character, the offspring will be CBAY (yel- 

 low), whose germ -cells will be of four kinds, CB, AY, CY, and 

 AB. Crossing this yellow mouse (with its four kinds of germ- 

 cells) with a white mouse, AGAB, obtained in the way just 

 described, eight possible combinations may follow. The whole 

 process is indicated in the following table : — 



Parents .4 G (albino) ^45 (albino) C5 (black) ^F (yellow) 



\ / \ / 



ist generation AGAB (albino) CBAV (yeliow) 



. AGCB gray (one) 



ABCB black (one) 



AGAY) 



2d generation AGAB ! ,, • /r ^ 



^ jlB^Y [albinos (four) 



ABAB J 



g];^2j yellow (two) 



Cuenot performed this experiment and obtained in the sec- 

 ond generation 151 young, distributed as follows according to 

 color : — 



81 albinos, 34 yellow, 20 black, 16 gray. 



The probabihty according to the formula 4/^ + 2 n-{-n-\-n is: 



76 albinos, 1,8 yellow, 19 black, 19 gray. 

 The agreement is so close that there can be httle doubt that the 

 hypothesis is substantially correct. 



Heredity of Piebald or Spotted Varieties. — The piebald condi- 

 tion is regarded by Cuenot as a special mutation, and not one 

 due to crossing colored and white forms. The piebald charac- 

 ter appears in crossing to be dominated by the uniform colora- 

 tion, whatever may be its tint. For example, a spotted gray- 

 and-white mouse crossed by a uniformly black mouse gives a 

 uniformly colored gray mouse, showing that the coupled 



