113 PROCEEDINGS OF THE AMERICAN ACADEMY. 



duced experimentally by simply crossing pigmented with albino indi- 

 viduals is well known (Darwin, '76), and although Crampe appears to 

 have been able to do so with his rats, nevertheless his results are capable 

 of another interpretation, in some cases at least. Thus Crampe ('85) 

 states that the wild gray rat or " species " bred to albinos gave animals 

 entirely gray or else animals with white in the forehead, tail, or belly. 

 Rats of the latter sort, if interbred, gave not only unicolored but spotted 

 young as well, and also albinos. In this case, however, the possibility is 

 not excluded that the so-called species was not an actual wild gray rat, but 

 simply one which was gray through reversion, and had had one spotted 

 parent. 



These f;\cts lead to a consideration of the behavior of the spotted or 

 partial albino condition in crosses. As previously stated, when two 

 pure-bred spotted individuals are mated, the young are all spotted. The 

 spotted character is quite independent of color, however, so that it is 

 possible to mate piebald mice, which differ in the color of their pig- 

 mented areas, and yet to obtain offspring all spotted. This shows that 

 the mosaic, if such it be, retains its integrity strongly, or in other words 

 tJie localization of the ingment at certain points is a condition which is 

 heritable. Yet the degree of this localization varies, and in a single litter 

 individuals may occur having pigment patches more or less extensive 

 than those of their parents. The important point is that breaks between 

 the pigmented areas do occur in the young of partially albino mice, be 

 these breaks large or small. 



A different result is obtained by breeding partial albinos to certain 

 stocks of complete albinos. In the writer's early experiments a large 

 number of young was obtained by breeding black-whites to albinos of a 

 stock whose ancestry was unknown. In all cases the resulting young 

 were practically totally pigmented. Some showed no trace of albinism 

 in the pelage, though others had white toes, or a white tip to the tail, or 

 even a few scattered white hairs. Only one had a white spot on the 

 belly. This is much the same result as that recorded by Haacke ('95), 

 who, in crosses of a Japanese spotted stock with albinos, obtained mice of 

 a uniform color over the entire body, save that in occasional animals 

 small flecks of white appeared in the usual places (i. e., on the forehead, 

 tail, or belly). Von Guaita ('98) by a similar cross obtained a like result. 

 The influence of the albinos in these cases seems to be to upset the con- 

 dition of localization of the pigment, so that the pigment patches become 

 more extensive, tending to cover the entire body surface as in totally pig- 

 mented animals. In explanation of this observation, it is suggested that 



