ACQUIRED CHARACTERS IN ANIMAL BREEDING 485 



mixis as a cause of variation, but he found other and abundant evidence 

 to confirm his scepticism. Even at the present time his reasons for the 

 opposing position are valid and sound. They may be stated briefly as 

 follows : 



1. There is no known mechanism by which the soma may influence 

 the germ-plasm in a specific fashion. 



2. The evidence which has been presented in support of the belief 

 in the inheritance of acquired characters in not a single case satisfies the 

 rigid requirements of an experimental proof. 



3. The theories of the continuity of the germ-plasm and of germinal 

 variation can account for all known facts of heredity without resorting 

 to the inheritance of acquired characters. 



These statements represent a formidable indictment of the belief 

 in the transmission of effects of somatic modification. Some of the 

 evidence in support of these statements is given in what follows. 



The Soma and Germ-plasm. That there is no known mechanism 

 by which the soma may influence the germ-plasm in a specific fashion is a 

 fact admitted alike by neo-Lamarckians and Weismannians. But, as the 

 former point out, an admission of this point by no means necessarily 

 includes a denial of the existence of such a mechanism. The present 

 knowledge of biochemical relations within the body is in a lamentably 

 inadequate condition to serve as a basis for either the denial or affirmation 

 of specific relations between body and stirp. 



Fortunately, however, some definite experiments have been performed 

 which throw light upon this question. Of experiments on ovarian 

 transplantation those of Castle and Phillips deserve the greatest confi- 

 dence because they were performed with animals the genetic behavior 

 of which was known. The account of one successful experiment follows: 



On January 6, 1909, the left ovary was removed from an albino guinea-pig, No. 

 27, then about 5 months old, and the ovary of a pure black guinea-pig about a month 

 old was fastened near the tip of the uterine horn, distant a centimeter or more from 

 the site of the ovary removed. One week later, January 13, a second operation was 

 performed, in which the right ovary of the albino was removed, and as a graft was in- 

 troduced the ovary of a second young black guinea-pig, of like age with the first 

 but of different ancestry. After the albino had fully recovered from the second 

 operation, she was placed with an albino male, No. 654 with which she remained until 

 her death about a year later. 



On the 23rd of July, 198 days after the operation, she gave birth to two female 

 young. One was black but bore a few red hairs. . . . The other young one 

 was likewise black, but had some red upon it, and its right forefoot was white. 



On October 15 the grafted albino bore a third young one, a male which, like those 

 previously borne, had a few red hairs interspersed with black .... 



On January 11, 1910, the grafted albino was observed to be pregnant for the third 

 time, and this time she was very large. Unfortunately, on February 2nd, she died of 

 pneumonia with three full-grown male young in utero. The skins of these animals were 



