CHAPTER V 



MENDELIAN HEREDITY 



IN the last chapter the distinction has more 

 than once been referred to between the statistical 

 rules of inheritance discovered by observing great 

 numbers of cases taken together, and the physio- 

 logical laws which determine the actual manner of 

 transmission in individual cases. The province of 

 the present chapter is to indicate the methods by 

 which one at least of these physiological laws has been 

 investigated, and the results to which such work 

 has led. In studying this part of the subject it is 

 necessary to consider, at least in the first place, 

 characters which vary and are inherited discontinu- 

 ously, so that they may be sharply marked into 

 distinct categories. The foundation of the study 

 was laid by Johann Gregor Mendel, a monk of the 

 monastery of Briinn in Bohemia. His most important 

 paper was published in 1866 [2], but perhaps owing 

 to the fact that the biological world was then 



