THE BIOMETRIC STUDY OF TTEREniTV 45 



Law works itself out. Nevertheless we must admit 

 that, from the special standpoint of the biometrician, 

 this law must appear to be all that Dr. Vernon 

 thinks it. 



Most valuable results have followed the work of 

 the bionietricians upon the variableness of such struc- 

 tures as leaves, hairs, or scales, which are repeated 

 in the bodv of the same individual orijanism. With- 

 out detailing the highly complex methods employed 

 in this study, and without noting certain tentative 

 results which may prove to be of great value, we 

 may pass at once to the bearing of these studies 

 upon the facts of bi-parental reproduction. The 

 reproductive cells must be regarded as " serial homo- 

 logues," the name applied to structures repeated in 

 the body of one individual. Now the comparative 

 study of brothers is plainly a means by which we can 

 study the variableness of the reproductive cells of 

 the father. But in the study of the production by a 

 man of repeated sex-cells, represented by his sons, 

 there is the obvious complication that the sons are 

 derived from their mother as well : the case is hardly 

 parallel to that of the repetition of leaves (which are 

 not sexually produced, of course) on the body of a 

 plant. But Pearson has made the very important 

 observation that the variableness of human children 

 " obeys the same law as that of other repeated struc- 

 tures." These biometric observations are of great 

 value in enabling us to reject Weismann's theory of 

 the function of bi-parental reproduction as a cause 

 of variations : for they unquestionably show that no 

 increase of variableness is associated with this 

 method of reproduction. Let us clearly understand 



