HEREDITY 149 



has made it possible to harmonize many of the observed 

 phenomena with the mendelian principle. It has also 

 directed the attention of investigators to the fundamental 

 nature of the characters themselves. Great progress 

 will undoubtedly be made in the future in the direction 

 of a more thorough study and consequently better under- 

 standing of the real nature of the characters of both plants 

 and animals. 



In the investigations on the eye color of man, it has 

 been found that the dominant character is due to a brown 

 pigment, while the recessive character is the result of the 

 absence of this pigment. Darbishire 1 has clearly indi- 

 cated the application of this theory in the case of the 

 round pea and the wrinkled pea. The quality of round- 

 ness or wrinkledness as found in the garden pea is due 

 to a difference in the amount of starch in the pea. In 

 the case of the wrinkled pea, all of the sugar content is 

 converted into starch. In the round pea a much more 

 complete transfer of sugar to starch is accomplished. 

 The inference is that in the round pea there is present 

 something in the germ-cell that so affects the physiological 

 processes in the cell that the sugar is more or less com- 

 pletely turned to starch. The something which deter- 

 mines this change of sugar to starch in the round pea is 

 absent from the germ-cell in the wrinkled pea.- There- 

 fore, we have two varieties of pea that are clearly different* 

 When the wrinkled pea and the round pea are crossed, 

 they behave in accordance with the mendelian law. It 

 is not necessary in this case to assume that the determiner 

 which ultimately results in a round pea is entirely absent 

 in the wrinkled pea, but it seems to be entirely correct 



1 Darbishire, "Breeding and the Mendelian Discovery," p. 

 127. 



