THE BIOMETRIC PROOF OF THE PURE LINE 

 THEORY 1 



DR. J. ARTHUR HARRIS 

 Carnegie Institution of Washington 



I. Introduction 

 On this platform I find myself in a somewhat embar- 

 rassing position. A friend assured me in advance that 

 this symposium would be somewhat analogous to the 

 country parson's "praise service," and into this pure 

 devotional atmosphere I must bring a note of agnostic- 

 ism. 



Agnosticism is a term selected after careful delibera- 

 tion. Johannsen's propositions are important — if true 

 — and any candid naturalist must hesitate before oppos- 

 ing a new theory which may lead to important advances 

 in biology. Agnosticism is the condition of mind tem- 

 porarily enforced by the results of my own experiments. 

 If one is pledged in advance to the pure line theory many 

 of these observations can be made to confirm Johann- 

 sen's conclusions. If one is unprejudiced and seeks to 

 fit his theories to his observations, rather than to adjust 

 his facts to his preconceived conclusions, the results are 

 quite as capable of other interpretation. Possibly more 

 extensive work may show clear confirmation of his re- 

 sults. Meanwhile I must withhold final judgment, 

 merely stating that my own work has greatly shaken my 

 confidence in Johannsen's theory. 



Here I do not care to dwell "upon details of my own 

 experiments. It seems more profitable to try and state 

 the fundamental problems of the pure line theory as 

 they appear to the biometrician and to indicate the 

 methods of work which seem to him necessary to the 

 drawing of sound conclusions. 



'From a symposium on "The Study of Pure Lines of Genotypes," 

 before the American Society of Naturalists, December 29, 1910. 



