The Inherilance of Acquired Characters 23 



be taken to suggest selection from an impure strain. If 

 his conception is true, it could be demonstrated by de- 

 veloping a large majority of resistant indiA'iduals among 

 the non-resistant j)lants which were first subjected to 

 disease attack, rather than merely ''a few scrubs." The 

 results as they stand could probably be interpreted as 

 due to the selection of a few resistant individuals from 

 an impure strain. 



From the foregoing cases, it becomes rather evident 

 that, so far as mutilations, effects of use and disuse, and 

 diseases are concerned, inheritance of acquired characters 

 has not as yet been satisfactorily demonstrated, either 

 in the plant or animal kingdom. One more category 

 of cases, however, remains to be considered. 



4. Effects of environment. — This heading is suffi- 

 ciently inclusive to include a number of types of cases. 



It has now been some years since Castle (6) per- 

 formed his classic experiment on guinea pigs. Animals 

 w^ith white coats will have only white-coated progeny, 

 while a pair with black coats, provided both male and 

 female come from a pure stock, will have only black- 

 coated progeny. Using only animals from pure stock, 

 Castle removed the ovaries from a white-coated female 

 and transplanted them into the body of a black-coated 

 female. The mating between this black-coated '^ foster 

 mother" and a white-coated male resulted in a progeny 

 all of which had white coats. Evidently it was the germ 

 cells alone that were effective in determining the char- 

 acter of the progeny. The decisive results of this experi- 

 ment were very influential in refuting the concept of 

 inheritance of acquired characters. At the same time 

 it must be borne in mind that, whereas such a superficial 



