4 ON GERMINAL TRANSPLANTATION IN VERTEBRATES. 



opposed tissues. Thus the results are greatly at variance. No doubt the 

 stock used by some of the workers in this field has been more or less closely 

 related. The ratio of success in such cases to the degree of relationship 

 of the opposing tissues has not been worked out, so far as we are aware. 



It is necessary to criticize workers in this group on the ground that many- 

 cases are considered successful if the ovary is found more or less normal 

 after short intervals days or weeks. This is no adequate test, as in many 

 of these cases degeneration is ultimately complete. 



Knauer' s results with his thirteen operations of homoplastic grafting were 

 negative except in two cases, in which the findings were by no means 

 conclusive. In spite of this Knauer thought that homoplastic grafts were 

 possible, though difficult. 



Fish (1899) experimented upon twenty rabbits with, he says, successful 

 results. He had hoped to establish the fact that conception is possible 

 subsequent to homoplastic ovarian transplantation, but in this he was dis- 

 appointed. His experiment is not given in detail. 



Foa (1900-1901) was led to undertake experiments in homoplastic graft- 

 ing", at the suggestion of Celisea, as a means of settling the controversy 

 between the Neo-Lamarckians and the Neo-Darwinians. He does not give 

 details of each experiment, and their number appears to have been small. 

 His grafts were made onto the original ovarian sites. With this method 

 one might question whether regenerated tissue could be distinguished from 

 grafted tissue. His conclusions were that homoplastic grafting was practical, 

 especially when ovaries of new-born animals were used as material to be 

 grafted. He thought that such material, planted into older animals, grew 

 much faster than normally and soon arrived at the growth stage of the 

 host, and he cites an experiment in support of this view. It is possible, 

 however, that regeneration of older tissue may have occurred in such cases 

 rather than accelerated development of introduced tissue. He says also 

 that ovaries of a new-born animal immediately degenerate when placed in 

 an older animal whose own ovaries have ceased to function. His findings 

 inclined him to the belief that there can not be such independence of ger- 

 minative material as the doctrine of Weismann would have us believe. 

 Experiments in which he hoped to show the influence of the foster-mother 

 upon foreign germinative material have not been heard from. 



Guthrie (1908) did homoplastic grafting of ovaries in chickens and ob- 

 tained young from his grafted animals. He concludes that the homoplastic 

 ovaries function normally and produce young. He thinks that the color 

 characteristics of the foetuses and of the chicks may be influenced by the 

 foster-mother. The detailed observations made may be summarized as 

 follows : 



Two pure-bred black single- comb Leghorn and two white single-comb 

 Leghorn pullets were operated upon, and a third pullet of each sort was 



