186 GEOkGE JOHN BOMANES 



18 Cornwall Terrace, Regent's Park, N.W. : January 7, 1887. 



Dear Darwin, Some time ago you write that I 

 ought to read a book or paper by Jordan about varieties 

 in relation to sterility. I cannot find any book or 

 paper of his at the L.S. library which treats of this 

 subject ; could you give me the name of his essay ? 



I am making arrangements for trying whether 

 there are any degrees of sterility to be found between 

 well-marked and constant varieties of plants. But 

 as I have never done anything in the way of hybrid- 

 ising, perhaps you would be good enough to let me 

 know whether the enclosed plan of experimenting 

 represents the full and proper way of going to work. 

 I know that you do not believe in the object of it, 

 but, even supposing it to be a wild-goose chase, there 

 would be no harm in your telling rne the best way to 

 run. Then, whether the results prove positive or 

 negative, it will not be open for any one to doubt 

 them on the ground of any fault in the method. 



Do any objections occur to you re my answer to 

 critics in the ' Nineteenth Century ' ? Of course I 

 might have said more about the swamping effects of 

 free intercrossing (which appears to me the only 

 point in which I deviate at all from the * Origin of 

 Species '), but it is much too large a subject to be 

 dealt with in a review. My greatest difficulty here 

 is to conceive the possibility of differentiation (as 

 distinguished from transmutation in linear series) 

 without the assistance of isolation in some form or 

 another. 



Yours very truly, 



GEO. J. ROMANES. 



