70 EXPERIMENTAL EVOLUTION LECT. 



the result of the climate of the sea-shore, and in fact, 

 , the descendants of these spotted animals bred inland, 

 at Lyons for instance, were always pure white. 1 



So much, then, for colour variation. But animals 

 and plants vary in many other respects, and one of 

 the most familiar examples is that of dimensional 

 differences. 



I am not aware that any naturalist has said 

 -unless in current English or French, happily not 

 in a Latin aphorism that dimensional differences 

 are of small importance ; but I presume many 

 think so. Variations of this sort are very frequent, 

 and although it is possible, by selection of extreme 

 variations, to create varieties of giant or of dwarfed 

 plants for instance, as any horticulturist may testify, 

 one might rightly consider this sort of variation as 

 more secondary than most others, if it could not be 

 shown that, while dimensions vary, other variations are 

 present at the same time, which may very well be of 

 high importance. These dimensional variations arc 

 in a large measure correlated with external influences. 

 Darwin has shown how, among horses, the dimensions 

 decrease in northern latitudes, in islands, and on moun- 

 tains. Man also is smaller in extreme northern climates, 

 and all the organisms of extreme northern parts 

 tend to be small. It may be, as Alcide d'Orbigny 



1 Fact quoted by Cornevin : Traitt de Zootechnie, p. 278, 



