192 1.] and their part in Evolution. 723 



Wlieatear, Blue and White Herons (Ardea rii/a) — all the 

 factors will be the same except one or two ; but on my 

 reasoning they are none the less good species, because they 

 do not contain exactly the same factors. Now all subspecies 

 of a given " unit " contain exactly the same factors ; but the 

 somatic expression of these factors .has been originally 

 altered by tlie environment, and subsequently become in- 

 herited. We have only to note in domestic types the 

 reversion, after some generations, to the wild form to prove 

 the truth that the factors have remained unchanged, but 

 that the alterations caused by environment (domestication) 

 have been so far inherited that the reversion is not complete 

 for several jjeneratious. 



Since the above was written, I have had the pleasure of 

 reading Colonel Meinertzhagen^s excellent article in the 

 current number of ' The Ibis,' p. 528, to one or two ])oints 

 of which I should like to refer. 



The author is of opinion that no deductions from 

 mutations carried out on domestic varieties can be of value, 

 since such conditions do not exist in Nature; but surelv by 

 carrying out heredity experiments under conditions which 

 we know, we are able the more accurately to attempt to 

 understand .the laws of heredity, and can then see if they 

 would apply to wild species under natural conditions. 



There is, to my way of thinking, no need to question 

 whether species arose by mutations or by gradual selection. 

 In the case of domestic freaks, which form but a small 

 proportion of domestic races, they probably originated as 

 mutations ; but by far the greater number of our " fancy '' 

 breeds to-day have been brought about by a process of 

 careful and minute selection in order to intensify or diminish 

 any particular trait or character ; and in that process each 

 generation would show a larger and increasing proportion of 

 individuals having that character, thus proving that not 

 only any particular character, but also its intensitication, 

 was inherited. The reason this fact is not fully recognized is 

 because of the compiiratively short i)eriods during which a 



