306 GEOBGE JOHN EOMANES 1893 



But I should like to know the species of wild fowl 

 which you have found to be hybridisable or cross- 

 fertile, so that I may ascertain whether their natural 

 breeding areas are, or are not, identical. Of course I 

 should expect them not to be. 



I have been told to save my eyes as much as 

 possible, and therefore conduct most of my corre- 

 spondence by dictation. But not being used to this 

 process, I find it even more difficult than before to 

 express my meaning with clearness, so I will tackle 

 with my own hand what you say about Aquilegias. 



I have looked up the group, and find that, with 

 the exception of vulgaris (common columbine), all 

 the European species seem to occupy restricted areas, 

 or else well-isolated stations. Also, that the same 

 seems to apply as a very general rule to other species 

 all over the world, for, wherever mountains are con- 

 cerned, stations are apt to be isolated by difference 

 of altitude, &c. 



Now if such be the case with the group in ques- 

 tion, the fact of its constituent species being freely 

 hybridisable when artificially brought together is 

 exactly what my theory requires. For the specific 

 differentiation has presumably been effected by 

 geographical (or topographical) isolation, without 

 physiological having had anything to do with it. 

 In fact, as stated over and over again in my original 

 paper, this correlation between geographical isolation 

 and cross-fertility is one of my hues of verification, 

 the other line being the correlation between identical 

 stations and cross-sterihty. 



Now, as above stated, I have found both these 



