236 METAMORPHOSIS AND 



with a normal white hen, and Davenport concludes 

 that the engrafted ovary was not functional but had 

 degenerated. It is known to be almost if not quite 

 impossible to remove the ovary completely from a 

 hen, owing to its close attachment over the great 

 post-caval vein. At the same time it is difficult to 

 see how Guthrie could have obtained black and 

 spotted chicks from a white hen mated with a white 

 cock if the grafted ovary from a black hen had not 

 been functional. One point which Guthrie does not 

 mention, and of which apparently he was not aware, 

 is that the white of the White Leghorn is dominant 

 to colour, the heterozygotes not being pure white but 

 white with spots. Thus when he mated a black cock 

 with a white hen with grafted ovary and obtained 

 spotted chicks, this would have been the result if 

 the original white ovary was functional. None of his 

 results prove conclusively the influence of the soma 

 of the hen into which ovaries were grafted, but would 

 all be explained if some eggs were derived from the 

 part of the original ovary not removed in the opera- 

 tion, and others from the grafted ovary. 



The grafting of ovaries in Mammals has often been 

 tried, but very rarely with success. The introduced 

 ovary usually dies and is absorbed. C. Foa ^ states 

 that he made bilateral grafts of ovaries from new- 

 born rabbits into adult rabbits, and two months 

 after the operation one of the operated females was 

 fecundated and produced five normal young. In 

 other cases he placed ovaries from new-born young 

 in positions far from the normal position, such as the 

 space between the uterus and bladder, and in one 

 case the female so treated became pregnant, and 



^ Arch. Ital, de Biol. (1901), Tome xxxv. 



