28 



MENDELISM 



CHAP 



and that these somethinefs whatever the\-ucrc could not 

 coexist in an\' sincfle cfamete. For these soinethinG[;s 

 we shall in future use the term factor. The factor, 

 then, is what corresponds in the gamete to the unit- 

 character that appears in some shape or other in 

 the development of the zygote. Tallness in the pea 

 is a unit-character, and the gametes in which it is 



Fig. 3. 



Two double .and an ordinary single primula llower. 



to the single. 



'J'lii> tunn ofdouide is recessive 



represented are said to contain the factor for tallness. 

 Beyond their existence in the gamete and their 

 mode of transmission we make no sucrnrestion as to 

 the nature of these factors.^ 



On Mendel's view there was a factor correspond- 



' Though in ihis parlicular instance in tlie pc;i there wouhl appear 

 to l)e a sliict ctjrrespondence between a unit-character and a factor, it 

 nuist not be taken that this is al\\a)s so clear. As will appear later, 

 the character in which two plants or animals of the same faniil\- differ 

 from one another may depend upon two or even more lactors. 



