DARWIN S43 



body of evidence, and your case of the Saturnia is 

 one of the most remarkable of which I have heard. 



In 1878 he fully included Wagner's theory as 

 one cause of origin of species, through the direct 

 action of environment in the same country or 

 through geographical isolation/ In 1877 also he 

 had written to Morse r "I quite agree about the 

 high value of Mr. Allen's works, as showing 

 how much change may be expected apparently 

 through the direct action of the conditions of 

 life." There is thus no doubt that the idea of nat- 

 ural selection, as almost the sole factor, came to 

 a climax in Darwin's mind and then gradually 

 appeared less supremely important and exclu- 

 sive. In preparing his work on Variation,' the 

 importance of the problem of heredity came be- 

 fore him, and in writing to Huxley, in 1865,^ he 

 gives a *brief ' of his point of view at the time, in 

 concisely stating what a working theory of hered- 

 ity should embrace: 



The case stands thus : in my next book I shall pub- 

 lish long chapters on bud- and seminal-variation, on 

 inheritance, reversion, effects of use and disuse, etc. 

 I have also for many years speculated on the different 

 forms of reproduction. Hence it has come to be a 

 passion with me to try to connect all such facts by 

 some sort of hypothesis. 



'^Life and Letters. Letter to Semper, November 30, 1878. 

 ^Loc. cit. Letter to Morse, April 23, 1877. 

 ^Loc. cit. Letter to Huxley, May 27, 1865 (?). 



