160 ON VARIABILITY AND ADAPTATION 



mission, upon in-breeding and marriage of consanguines, upon 

 degeneration as distinct from atavism, upon the particular 

 problems of inheritance of nervous conditions, to mention 

 but a few. It seems to me, however, that this conception of 

 the properties of idioplasm is adequate to bring together and 

 harmonize the facts we possess concerning all of the above- 

 mentioned conditions. 



Let me conclude with Weismann's apology : " Hypotheses, 

 even when not absolutely right, may be of value in advancing 

 our knowledge, if only they are relatively right, i.e. when they 

 correspond with the state of existing knowledge. They are 

 like the feelers which the short-sighted snail stretches forth on 

 its darkened path, testing this way and that, and withdrawing 

 them and altering the route so soon as they come across any 

 obstacle." x 



I must ask your forgiveness for bringing before you a 

 subject so far outside the line of general medical thought, 

 and for having inflicted on you so much that is theoretical. 

 That was not my intention when I sat down to prepare the 

 paper. I had intended to indulge in the main in a destructive 

 criticism, to point out how Weismann's and allied theories fail 

 to satisfy certain orders of conditions presenting themselves to 

 medical men ; but as I proceeded with the task it became 

 obvious that mere destructive criticism was valueless, that it 

 became imperative to present an alternative theory which for 

 many months — I may truly say years — had been simmering 

 within me, unexpressed. 



1 Weismann, loo. cit., Introductory Note. 



