28 



MENDELISM 



and that these somethings whatever they were could not 

 coexist in any single gamete. For these somethings 

 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 douljle and an ordinary- single primula flower. Tllis form of double is recessive 

 ti:) the single. 



represented are said to contain the factor for tallness. 

 Beyond their existence in the gamete and their 

 mode of transmission we make no suggestion as to 

 the nature of these factors.' 



On Mendel's view there was a factor correspond- 



1 Thoiigli in this p.irlicul.ir instance in tlie pea there would appear 

 to Ije a strict correspondence between a unit-character and a factor, it 

 must not Ije taken that this is always so clear. As will appear later, 

 the character in which two plants or animals of the same family differ 

 from one another may depenil upon two or even more factors. 



