The Perpetuation of Living Beings, Hereditary Transmission and Variation | Page 9

place in the case of Seth Wright's sheep,
where it happened to be a matter of moment to him to obtain a breed or
raise a flock of sheep like that accidental variety that I have
described--and I will tell you why. In that part of Massachusetts where
Seth Wright was living, the fields were separated by fences, and the
sheep, which were very active and robust, would roam abroad, and
without much difficulty jump over these fences into other people's
farms. As a matter of course, this exuberant activity on the part of the
sheep constantly gave rise to all sorts of quarrels, bickerings, and
contentions among the farmers of the neighbourhood; so it occurred to
Seth Wright, who was, like his successors, more or less 'cute, that if he
could get a stock of sheep like those with the bandy legs, they would
not be able to jump over the fences so readily, and he acted upon that
idea. He killed his old ram, and as soon as the young one arrived at

maturity, he bred altogether from it. The result was even more striking
than in the human experiment which I mentioned just now. Colonel
Humphreys testifies that it always happened that the offspring were
either pure Ancons or pure ordinary sheep; that in no case was there
any mixing of the Ancons with the others. In consequence of this, in
the course of a very few years, the farmer was able to get a very
considerable flock of this variety, and a large number of them were
spread throughout Massachusetts. Most unfortunately, however--I
suppose it was because they were so common--nobody took enough
notice of them to preserve their skeletons; and although Colonel
Humphreys states that he sent a skeleton to the President of the Royal
Society at the same time that he forwarded his paper, I am afraid that
the variety has entirely disappeared; for a short time after these sheep
had become prevalent in that district, the Merino sheep were introduced;
and as their wool was much more valuable, and as they were a quiet
race of sheep, and showed no tendency to trespass or jump over fences,
the Otter breed of sheep, the wool of which was inferior to that of the
Merino, was gradually allowed to die out.
You see that these facts illustrate perfectly well what may be done if
you take care to breed from stocks that are similar to each other. After
having got a variation, if, by crossing a variation with the original stock,
you multiply that variation, and then take care to keep that variation
distinct from the original stock, and make them breed together,--then
you may almost certainly produce a race whose tendency to continue
the variation is exceedingly strong.
This is what is called "selection"; and it is by exactly the same process
as that by which Seth Wright bred his Ancon sheep, that our breeds of
cattle, dogs, and fowls, are obtained. There are some possibilities of
exception, but still, speaking broadly, I may say that this is the way in
which all our varied races of domestic animals have arisen; and you
must understand that it is not one peculiarity or one characteristic alone
in which animals may vary. There is not a single peculiarity or
characteristic of any kind, bodily or mental, in which offspring may not
vary to a certain extent from the parent and other animals.

Among ourselves this is well known. The simplest physical peculiarity
is mostly reproduced. I know a case of a man whose wife has the lobe
of one of her ears a little flattened. An ordinary observer might scarcely
notice it, and yet every one of her children has an approximation to the
same peculiarity to some extent. If you look at the other extreme, too,
the gravest diseases, such as gout, scrofula, and consumption, may be
handed down with just the same certainty and persistence as we noticed
in the perpetuation of the bandy legs of the Ancon sheep.
However, these facts are best illustrated in animals, and the extent of
the variation, as is well known, is very remarkable in dogs. For
example, there are some dogs very much smaller than others; indeed,
the variation is so enormous that probably the smallest dog would be
about the size of the head of the largest; there are very great variations
in the structural forms not only of the skeleton but also in the shape of
the skull, and in the proportions of the face and the disposition of the
teeth.
The Pointer, the Retriever, Bulldog, and the Terrier, differ very greatly,
and yet there is every reason to believe that every one of these races has
arisen from the same source,--that all the most important races