HEREDITY 



kept in captivity arise chiefly from loss or 

 modification of Mendelian unit-characters. 

 Loss of a unit-character might easily come 

 about by an irregular cell-division in which 

 the material basis of a character failed to 

 split, as normally. The consequence would be 

 that the character in question would be trans- 

 mitted by one only of the two cell-products 

 produced. The cell lacking a character might 

 be the starting-point of a race lacking the char- 

 acter, as of a black race, derived from a gray 

 one. On the other hand a modified condition 

 of a unit-character might possibly result from 

 unequal division of the material basis of a 

 character, so that one of the cell-products 

 would transmit the character in weakened in- 

 tensity, the other in increased intensity. 



BIBLIOGRAPHY 



CASTLE, W. E. 



1907. "Color Varieties of the Rabbit and of Other Rod- 

 ents: Their Origin and Inheritance." Science, N. S., 

 26, pp. 287-291. 



1908. "A New Color Variety of the Guinea-pig." Science, 

 N. S., 28, pp. 250-252. 



1909. "Studies of Inheritance in Rabbits." Carnegie 

 Institution of Washington, Publication No. 114, 70 pp., 

 4 pi. 



86 



