EMBRYOLOGY 257 



bryology. But first let us look to a few analogous cases 

 in our domestic varieties. Some authors who have writ- 

 ten on Dogs, maintain that the greyhound and bulldog, 

 though so different, are really closely allied varieties, 

 descended from the same wild stock; hence I was curious 

 to see how far their puppies differed from each other: 

 I was told by breeders that they differed just as much 

 as their parents, and this, judging by the eye, seemed 

 almost to be the case; but on actually measuring the old 

 dogs and their six-days-old puppies, I found that the 

 puppies had not acquired nearly their full amount of pro- 

 portional difference. So, again, I was told that the foals 

 of cart and race-horses — breeds which have been almost 

 wholly formed by selection under domestication — differed 

 as much as the full-grown animals; but having had care- 

 fuls measurements made of the dams and of three-day-old 

 colts of race and heavy cart-horses, I find that this is by 

 no means the case. 



As we have conclusive evidence that the breeds of 

 the Pigeon are descended from a single wild species, 

 I compared the young within twelve hours after being 

 hatched; I carefully measured the proportions (but w^ill 

 not here give the details) of the beak, width of mouth, 

 length of nostril and of eyelid, size of feet and length of 

 leg, in the wild parent- species, in pouters, fantails, runts, 

 barbs, dragons, carriers, and tumblers. Now some of 

 these birds, when mature, differ in so extraordinary a 

 manner in the length and form of beak, and in other 

 characters, that they would certainly have been ranked 

 as distinct genera if found in a state of nature. Bat 

 when the nestling birds of these several breeds were 

 placed in a row, though most of them could just be 



