158 THE BEHAVIOR OF UNIT 



further to imitate the organic chemist by placing 

 a subscript, 2, after each factor doubly represented 

 in the individual, i.e. after every factor in which 

 the individual is homozygous, while elsewhere 

 omitting it. We shall thus have a zygotic for- 

 mula which will look like a chemical formula, and 

 which will serve the same useful purpose of ex- 

 pressing many facts clearly and in small com- 

 pass. 



The zygotic formula of the pure gray rabbit 

 will then be B2 E2 A2 C2 I2 U2 ; the gray rabbit 

 which also gives black young will be single in A, 

 but otherwise identical in formula with the fore- 

 going, viz., B2 E2 A C2 I2 U2, and so on through 

 the list. 



The question will naturally suggest itself, how 

 common are unit characters? Are all the quali- 

 ties and parts of organisms due to them, or only 

 certain lands of qualities or parts? Such ques- 

 tions can not at present be answered satisfac- 

 torily. It may be pointed out, however, tha*: »ve 

 are already acquainted with a considerable va- 

 riety of Mendelizing characters. These include 

 in plants both structural and physiological char- 

 acters of stem, leaf, flower, and seed. In ani- 

 mals, where a less extensive study has as yet been 

 made and where the organization is much more 

 complex, the unit characters thus far identified 

 relate chiefly to superficial characters, pigmenta- 

 tion, hair-structure, and the hke. Certain pecu- 

 liar variations of the skeleton, digital variations, 



