84 Experimental Zoology 



different according to the kind of albinos that he used. For 

 example, albinos that had been derived through a gray ancestor, 

 i.e. the so-called extracted albinos, when bred with the black 

 strain produced gray offspring. If, however, albinos that had 

 been derived through a previous cross with a black mouse were 

 bred with a black, the offspring were black. Again, albinos 

 derived from a previous cross with a yellow gave either mixed 

 yellow and gray, or mixed yellow and black. These results 

 show that although albinos may all appear ahke and breed per- 

 fectly true with each other, they belong in reahty to different 

 classes, whose latent characters are dependent on previous 

 influences. Results of this sort are difficult to account for on 

 the supposition that the germ-cells are pure. This property of 

 latency is not something peculiar to albinos as certain pubHshed 

 statements might have lead one to infer, but holds for the differ- 

 ent colors also. A black race that breeds true may carry 

 another latent color that can be brought out by crossing. Un- 

 less this fact is also taken into account the crosses with albinos 

 may be misinterpreted. 



Experiments with waltzing mice have been made by Haacke, 

 von Guaita, and Darbishire. These mice are black, or 

 white, or yellow and white; the mixed colors introducing 

 a compHcation into the results, so far as color inheritance 

 is concerned. As has been said, von Guaita's results with 

 these mice were not considered from the point of view 

 of Mendel's law, but Bateson, w^ho has later analyzed the data, 

 finds in some cases what seems to be an approximation to 

 the expected proportions; in other cases this is not evident. 

 A few of von Guaita's facts and their possible interpreta- 

 tions may be given. When the black-and-white waltzers were 

 bred to ordinary albinos, the first offspring {F^ were gray, hke 

 the house mouse, and of the same size, which is larger than 

 that of the waltzing race. They also show the wild disposition. 

 These mice (F^) when inbred produced albinos and four colored 

 types, — black, gray, black-and-white, and gray- and- white. 

 There were 14 albinos and 30 colored individuals. The relation 



