1894 EXPEEIMENTS ON HEEEDITY 341 



you the passages when we meet. But even in cases 

 of 'local varieties,' where a variety has a habitat 

 of its own surrounded by the tyj^e-form, I should 

 expect experiment would often (though by no means 

 always) show some degree of cross- infertility between 

 the two, pointing to prepotency (;i.e. early stages of 

 physiological selection) being the origin of the diver- 

 gence. 



Before we meet I \\ish you would try to think of 

 any plants which can be propagated by cuttings (or 

 otherwise asexually) which are known to be modifi- 

 able by changed conditions of life in the first genera- 

 tion. I understand you that in some cases the seed 

 of such a plant will not revert — when sown in its 

 natural environment, though, of course, the rule is 

 that it does. Well, in either case, I should much 

 like to try whether a cutting &c. from the trans- 

 planted (and therefore modified) tubers &c. would 

 revert to its ancestral character. When retrans- 

 planted to its natural environment, much would 

 follow from result of such an experiment as regards 

 Weismannism. 



Yours very and always truly, 



Gr. J. EOMANES. 



P.S. — Of course in saying 'on common areas, 

 sexual differentiation is the only means of securing 

 the isolation,' I did not include self -fertilising plants 

 — any more, e.g. than insect fertilising where changes 

 in the instincts of insects may cause sexual isola- 

 tion. 



I leave for Oxford to-morrow. 



