136 THE AMERICAN NATURALIST [Vol. XL VI 



made the experiment of engrafting foreign ovaries into 

 foster mothers very unlike the original females whence 

 they were taken. He concluded that the offspring were 

 modified in such a way as to prove that the transplanted 

 germ-plasm had received something from the foster 

 mother. Unfortunately Guthrie erred here, as my repeti- 

 tion of his experiments showed. For unquestionably, the 

 hens that were operated upon regenerated their proper 

 ovaries and produced no eggs from the engrafted ovaries. 

 Dr. Phillips, working with Castle, engrafted black-bear- 

 ing eggs from one female guinea pig into albino guinea 

 pigs and then mated the females that had been operated 

 upon with an albino male. All offspring were entirely 

 black, proving, first, that the engrafted ovaries were 

 functional and, second, that the determiners of the en- 

 grafted germ-plasm were not modified by the soma of the 

 albino mother. On the other hand, the experiments of 

 Standfuss, Tower and Kammerer on animals and Mac- 

 Dougal on plants apparently indicate that under the 

 influence of various conditions of moisture, temperature 

 and chemical action the germ-plasm may be changed. 

 These results, probable as they are, await confirmation. 

 If fully confirmed they will afford a picture of one way 

 in which new determiners may originate. 



Finally, some light has been thrown by modern experi- 

 mental studies on the subject of adaptation — for Darwin 

 the corner stone of organic evolution. But here, it must 

 be confessed, the contribution has not been great. That 

 there is such a thing as selective elimination is plainer 

 than ever. That some characteristics are compatible 

 with the environment and some incompatible is incon- 

 testibly true. Two cases in poultry illustrate this. I 

 have a lot of rumpless fowl ; the cocks are sexually active 

 and the hens lay numerous eggs ; but every egg is sterile, 

 for the reason that the erection of the tail feathers in the 

 hen is essential to the clean exposure of the cloacal open- 

 ing for the transfer of the sperm. Hence, since in the 

 rumpless hens the cloacal opening is not accessible to the 



