3M 



GEXERAL BIOLOGY 



lished by its founder, is represented in the accompanying 

 table (after Castle). 



Castle has proved by breeding experiments that in guinea- 

 pigs length, pigmentation and roughness of coat are hair 

 characters that are separately heritable, and that in crossing 

 they follow fairly Mendel's laAV. And he summarizes his 

 observations as follows: 



"This experiment illustrates two important principles in 

 heredity: First, if as regards the hair alone there exists 

 such a variety of characters separately inheritable, how 

 great must be the number of such characters in the body as 

 a whole, and how remote the probability that any animal 

 will in all characters resemble any individual ancestor, pro- 

 vided that in a considerable number of heritable characters 

 a choice is offered between alternative conditions. Secondly, 

 the experiment shows how a variety of new organic forms 

 may quickly be produced by cross-breeding, leading to the 

 combination in one race of characters previously found 

 separately in different races. Thus, in guinea-pigs, one can 

 obtain within two generations any desired combination of 

 the three pairs of alternative coat-characters, if one pro- 

 duces a sufficiently large number of individuals. 



