VIRILE SENTIMENT 71 



purity and segregation are tlie two processes which 

 determine human heredity, alike in the transmission 

 of normal and abnormal characters. 



Let us pass on, therefore, to consider some of the 

 evidence for segregation and gametic purity in 

 man. I propose first to deal with the transmission 

 of a normal human character, i.e., eye-colour. Until 

 Mr. Hurst, during the years 1905-1907, examined a 

 number of families, separately and in detail, recording 

 each individual eye-colour, it cannot be said that 

 our knowledge of tliis matter was anything like 

 definite or satisfactory. Previous records largely 

 depended upon the observations of different ob- 

 servers, and upon a more or less popular and in- 

 definite classification of eye-colours. And, moreover, 

 the mathematical methods that were employed to 

 deal with the ascertained data were of such a nature 

 that the truth was rather masked than elucidated by 

 them. As a matter of subsequent knowledge, they 

 actually did miss the truth. Mr. Hurst made a 

 personal examination of the eye-colours of one 

 hundred and thirty-nine pairs of parents, and of 

 six hundred and eighty-three of their offspring. 

 He found that he was enabled to classify all eye- 

 colours into two classes, which he called the " Sim- 

 plex " and the " Duplex." These two types of 

 eyes are quite distinct. The simplex type includes 

 all the pure blue and pure grey* eyes, i.e., blue and 



* Pure grey eyes are simply blue eyes in which the iris tissues are a 

 little more opaque, and so cause the blue to appear grey. Eyes which 

 are blue in childhood ma}- become grey in later life, owing to an increase 

 of this opacity. 



