no THE KALLIKAK FAMILY 



transmitted from parent to offspring in a definite way. 

 His classical work was on the propagation of the ordi- 

 nary garden pea, in which case he found that a quality 

 like tallness, as contrasted with dwarfness, was trans- 

 mitted as follows : 



If tall and dwarf peas were crossed, he found in the 

 first generation nothing but tall peas. But if these 

 peas were allowed to grow and fertilize themselves, in 

 the next generation he got tall and dwarf peas in the 

 ratio of three to one. The dwarf peas in this case bred 

 true, i.e. when they were planted by themselves and 

 self-fertilized there was never anything but dwarf peas, 

 no matter how many generations were tested. On the 

 other hand, the tall peas were divisible by experiment 

 into two groups ; first, those that always bred true, 

 viz. always tall peas ; and secondly, another group that 

 bred tall and dwarf in the same ratio of three to one ; 

 and from these the same cycle was repeated. Mendel 

 called the character, which did not appear in the first 

 generation (dwarfness), "recessive"; the other (tall- 

 ness) he called "dominant." The recessive factor is 

 now generally considered to be due to the absence of 

 something which, if present, would give the dominant 

 factor. According to this view, dwarfness is simply 

 the absence of tallness. 



