mSTORICAL ACCOUNT OF EVOLUTION THEORY 41 



who were engaged in crossing the garden peas with a view to producing 

 more vigorous and productive varieties, and Naudin (1862) in France, 

 who made a comprehensive survey of the facts of hybridization in 

 plants and came very near to expressing the generalization which 

 Mendel reached four years later." 



Mendel's laws 



"The earliest experimental investigations of heredity," says 

 Locy' in a concise summary of Mendel's work, "were conducted with 

 plants, and the first epoch-making results were those of Gregor Mendel 

 (1822-1884), a monk and later abbot, of an Augustinian monastery at 

 Briiim, Austria. In the garden of the monastery, for eight years 

 before pubhshing his results, he made experiments on the inheritance 

 of individual (or unit) characters in twenty-two varieties of garden 

 peas. Selecting certain constant and obvious characters, as color, and 

 form of seed, length of stem, etc., he proceeded to cross these pure 

 races, thus producing hybrids, and thereafter, to observe the results of 

 self-fertilization among the hybrids. 



"The hybrids were produced by removing the unripe stamens of 

 certain flowers and later fertilizing them by ripe pollen from another 

 pure breed having a contrasting character. The results showed that 

 only one of a pair of unit characters appeared in the hybrid of the next 

 generation, while the other contrasting character lay dormant. Thus, 

 in crossing a yellow-seeded with a green-seeded pea, the hybrid genera- 

 tion showed only yellow seeds. The character thus impressing itself 

 on the entire progeny was called dominant, while the other that was 

 held in abeyance was designated recessive. 



" That the recessive color was not blotted out was clearly demon- 

 strated by allowing the hybrid generation to develop by self-fertiliza- 

 tion. Under these circumstances a most interesting result was 

 attained. The filial generation, derived by self-fertilization among 

 the hybrids, produced plants with yellow and green seeds, but in the 

 ratio of three yellow to one green. All green-seeded individuals and 

 one-third of the yellow proved to breed true, while the remaining two 

 thirds of the yellow-seeded plants, when self-fertilized, produced 

 yellow and green seeds in the ratio of three to one. 



" Subsequent breedings gave an unending series of results similar 

 to those obtained with the first filial generation. 



' William A. Locy, The Main Currents of Zoology (Henry Holt & Company, 

 igi8), pp. 37-30- 



