258 president's address. — section d. 



from the operation, the animal was mated wih an albino male. As 

 albinism is in guinea-pigs recessive, there is no question as to the 

 homozygous character of the grafted animal, nor as to that of her mate. 

 Evidently, if she should prove to influence the colour of her offspring, 

 they would be white. 



The first litter consisted of two female animals, both black. One 

 had a few red hairs, and the other had some red upon it, and had a 

 white fore-foot. It will presently be shown what reason there is for 

 regarding these peculiarities as derived solely from the father. 



As a result of a second mating with the same animal, the grafted 

 albino produced a black male, having a few red hairs. 



During a third pregnancy she died of pneumonia. The uterus 

 was found to contain three well-developed male young. They Avere 

 all black, with a few red hairs among the black. 



With regard to the grafted albino herself, the autopsy showed that 

 the left grafted ovary was well-developed and functional. On the 

 right side, presumably in the position of the graft, ovarian tissue was 

 found, but so encapsulated that eggs could not be discharged even if 

 they came to maturity. 



In considering the results of these matings, it is important to 

 remember that all the male gametes bore the factor for whiteness. 

 If, therefore, any of the female gametes concerned had borne that 

 factor, there would have been albinos among the offspring. 



It may be objected that a total offspring of six does not furnish a 

 convincing number of cases ; and it is, of course, arguable that, if the 

 mother had lived long enough to enable the experiments to be made with 

 germinal material matured later in her life and (possibly) less affected by 

 the ovarian mother or her tissue, there m-ight have been different results. 

 It must, however, be admitted that, if in six gametes taken at chance 

 none bore the factor w, the expectation of that factor occurring in a 

 larger number cannot be a confident one. With regard to the second 

 possible objection, it is to be remembered that the grafting was done 

 nearly a year before the animal's death, and that pregnancy occurred 

 three times. 



The control experiments throw light on the source from which the 

 young animals referred to above derived one of their peculiarities — 

 the presence of some red hairs interspersed with the black. The albino 

 male of the experiments was, in control experiments, mated with a 

 pure black female. Five animals were produced in two litters. All 

 were black, vv'ith red hairs interspersed. The 'presence of red hairs in 

 the experiments of both sets may therefore confidently be regarded as 

 due to the influence of the father. It is known that he came of a race 

 characterized by spotting, and there v,-ere spotted members in the 

 litter in which he was produced. The white fore-foot of one of the 



