old dogs and their six-days-old puppies, I found that the puppies had not acquired nearly their full amount of proportional 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 careful measurements made of the dams and of three-days-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 pigeons within twelve hours after being hatched.

I carefully measured the proportions (but will not here give the details) of the beak, width of mouth, length of nostril and of