Chap. VI. MANNER OF FORMATION OF THE CHIEF RACES. 213 



considerably different conditions ; for they cannot obtain their 

 natural diversity of food ; and, what is probably more important, 

 they are abundantly fed, whilst debarred from taking much ex- 

 ercise. Under these circumstances we might expect to find, 

 from the analogy of all other domesticated animals, a greater 

 amount of individual variability than with the wild pigeon; 

 and this is the case. The want of exercise apparently tends to 

 reduce the size of the feet and organs of flight ; and then, from 

 the law of correlation of growth, the beak apparently becomes 

 affected. From what we now see occasionally taking place in our 

 aviaries, we may conclude that sudden variations or sports, such 

 as the appearance of a crest of feathers on the head, of feathered 

 feet, of a new shade of colour, of an additional feather in the 

 tail or wing, would occur at rare intervals during the many 

 centuries which have elapsed since the pigeon was first domes- 

 ticated. At the present day such "sports" are generally 

 rejected as blemishes; and there is so much mystery in the 

 breeding of pigeons that, if a valuable sport did occur, its history 

 would often be concealed. Before the last hundred and fifty 

 years, there is hardly a chance of the history of any such sport 

 having been recorded. But it by no means follows from this that 

 such sports in former times, when the pigeon had undergone 

 much less variation, would have been rejected. We are profoundly 

 ignorant of the cause of each sudden and apparently spontaneous 

 variation, as well as of the infinitely numerous shades of dif- 

 ference between the birds of the same family. But in a future 

 chapter we shall see that all such variations appear to be the 

 indirect result of changes of some kind in the conditions of life. 



Hence, after a long course of domestication, we might expect to 

 see in the riigeon much individual variability, and occasional 

 sudden variations, as well as slight modifications from the lessened 

 use of certain parts, together with the effects of correlation of 

 growth. But without selection all this would produce only a 

 trifling or no result ; for without such aid differences of all kinds 

 would, from the two following causes, soon disappear. In a 

 healthy and vigorous lot of pigeons many more young birds are 

 kdled for food OT die than are reared to maturity ; so that an 

 individual having any peculiar character, if not selected, would 

 run a good chance of being destroyed ; and if not destroyed, the 



