ALLEN. — THE HEREDITY OF COAT COLOli LN MICE. 101 



the secoud was of G entirely gray mice. Referring ugaiii to the exiun- 

 ple giveu under Case II, it is seeu that the six gray mice of geueration 

 Fj are theoretically of two sorts, D'DR and DR"R. The only union 

 by which albinos couUl be obtained from these parents is that of two 

 DRR individuals. That it tvas this uuion which produced the litter of 1 

 chocolate and 1 albino, seems to be additionally proved by the occurrence 

 of the chocolate individual. No case is as yet recorded in which the house 

 mouse in the second generation from across with albinos has produced choco- 

 late young, hence it is more than likely that the young one of this color 

 inherited that character directly from the chocolate-white grandfather ; that 

 is, either two DR gametes or a DR and an R gamete united to produce 

 it, so that its parents were both of the DRR class. The fact that there 

 were no albinos among the 6 individuals of the second litter probably 

 indicates that the parents were in this case either two D'DR individuals 

 or a D-DRand a DRR., neither of which combinations would result in the 

 production of albino offspring. 



As a means of testing the relations of the three characters involved in 

 a case of this sort, some of the statistics given by Crampe ('85) appear to 

 be applicable. This investigator details a number of litters obtained by 

 inbreeding the members of a single family, wherein there is evidence 

 that the three characters, which have just been considered, were present. 

 Thus on page 604 he gives a table containing the results of inbreeding de- 

 rivatives of '' species " by albino (Compare Table M). Since there occur 

 imraerous spotted young in the progeny, it is hardly to be doubted that 

 what Crampe thought was the " species " was really a heterozygous 

 (D*DR) individual containing both the character total pigmentation and 

 that of partial pigmentation. This interpretation is rendered still more 

 probable by the fact that these animals were of " variety 6," i.e. black 

 with traces of white on toes or tail, a condition which is often seen in 

 mice from wholly pigmented and spotted parents. Another table of the 

 same kind (see Table N) is given on p. 603 of the " Farben-Inzucht, 

 Farben-Reinzucht und Farbenkreuzung " in Family H. This family also 

 had the three characters D, DR, and R, represented among its members, 

 as the table of ancestry shows, for albinos, " species," and spotted animals 

 are hopelessly intermingled. A third table, on p. 612 (see Table O), 

 furnishes additional data of the same sort, where gray-whites are inbred 

 from a cross of " species " with a heterozygous black-white rat (DR-R). 

 The exact nature of all the matings cannot be known, but it appears that 

 " families " of rats in many cases, at least, were kept together, so that 

 there was every chance for random mating, and the totals given may 



