16 ON GERMINAL TRANSPLANTATION IN VERTEBRATES. 



tail." This is such a result as we should expect had the hen not been oper- 

 ated upon at all. It is fully accounted for if we assume that the ova which 

 produced these twelve chicks came from regenerated ovarian tissue of the 

 white mother herself. On the other hand, if the transplanted ovary had 

 produced the chicks without any foster-mother influence, the chicks should 

 have been all black with light ventral surfaces, which they were not. Again 

 the regeneration hypothesis presents far less difficulty than that of a suc- 

 cessful transplantation. 



Series II. Rooster White. 



White hen W 1 control, mated with the white rooster, had eighteen chicks 

 "pure white to light buff when hatched." White hen W2 and black hen 

 B 2 had their ovaries exchanged, and were later bred to the white rooster. 



Black hen B 2 produced nine white chicks and 11 white spotted sparingly, 

 with black. Such a result as this is the usual consequence of a cross 

 between black fowls and white ones; that is, it is what might have been 

 expected had the black hen never been operated upon. And, on the other 

 hand, if the functional ova came from the transplanted ovary, the expectation 

 would not be materially different, though the breeding capacity of the young 

 would be different in the two cases. Unfortunately this was not tested. 



The white hen W2, which had received the black ovary from B 2, pro- 

 duced five chicks. Three were white, one white spotted with black, and 

 one black. A white hen not operated upon might be capable of producing 

 all three sorts when mated with a white rooster of a similar character; 

 that is, both parents might be Mendelian heterozygotes bearing black as 

 a recessive character, in which case one-quarter of the young should be 

 black. Now, the numerical result is not at variance with such an interpre- 

 tation. But if the same white rooster was used in this mating as with B 2, 

 it is surprising that no black young were produced by B 2. Guthrie does 

 not expressly state that the same rooster was used in both cases, but we 

 assume this to have been the case from his use of the expression "the white 

 rooster." If different males were used in the two cases, one may well have 

 been homozygous, the other heterozygous. In that case the black chick 

 as well as the white and the spotted ones may have come from regenerated, 

 not from transplanted tissue. But if the same white rooster was used in 

 both cases, it is still equally difficult to account for the black chick as a 

 product of a transplanted germ-cell or of regenerated ovarian tissue of the 

 white mother. For unless the white male was heterozygous in black we 

 should expect no black young to be produced even were every egg which he 

 fertilized produced by a pure-black hen, instead of by a white hen possibly 

 carrying borrowed black germ-cells. 



Control matings of the white rooster with normal black hens, or of the 

 black chick when it became adult, would have cleared up the case, but no 

 control crosses were made by Guthrie. The control mating of "the white 

 rooster" with a normal white hen Wl was not a sufficient control of his 



