The Perpetuation of Living Beings, Hereditary Transmission and Variation | Page 7

commonly known as external
conditions,--such as temperature, food, warmth, and moisture. In the
long run, every variation depends, in some sense, upon external
conditions, seeing that everything has a cause of its own. I use the term
"external conditions" now in the sense in which it is ordinarily
employed: certain it is, that external conditions have a definite effect.
You may take a plant which has single flowers, and by dealing with the
soil, and nourishment, and so on, you may by-and-by convert single

flowers into double flowers, and make thorns shoot out into branches.
You may thicken or make various modifications in the shape of the
fruit. In animals, too, you may produce analogous changes in this way,
as in the case of that deep bronze colour which persons rarely lose after
having passed any length of time in tropical countries. You may also
alter the development of the muscles very much, by dint of training; all
the world knows that exercise has a great effect in this way; we always
expect to find the arm of a blacksmith hard and wiry, and possessing a
large development of the brachial muscles. No doubt training, which is
one of the forms of external conditions, converts what are originally
only instructions, teachings, into habits, or, in other words, into
organizations, to a great extent; but this second cause of variation
cannot be considered to be by any means a large one. The third cause
that I have to mention, however, is a very extensive one. It is one that,
for want of a better name, has been called "spontaneous variation;"
which means that when we do not know anything about the cause of
phenomena, we call it spontaneous. In the orderly chain of causes and
effects in this world, there are very few things of which it can be said
with truth that they are spontaneous. Certainly not in these physical
matters,--in these there is nothing of the kind,--everything depends on
previous conditions. But when we cannot trace the cause of phenomena,
we call them spontaneous.
Of these variations, multitudinous as they are, but little is known with
perfect accuracy. I will mention to you some two or three cases,
because they are very remarkable in themselves, and also because I
shall want to use them afterwards. Reaumur, a famous French naturalist,
a great many years ago, in an essay which he wrote upon the art of
hatching chickens,--which was indeed a very curious essay,--had
occasion to speak of variations and monstrosities. One very remarkable
case had come under his notice of a variation in the form of a human
member, in the person of a Maltese, of the name of Gratio Kelleia, who
was born with six fingers upon each hand, and the like number of toes
to each of his feet. That was a case of spontaneous variation. Nobody
knows why he was born with that number of fingers and toes, and as
we don't know, we call it a case of "spontaneous" variation. There is
another remarkable case also. I select these, because they happen to

have been observed and noted very carefully at the time. It frequently
happens that a variation occurs, but the persons who notice it do not
take any care in noting down the particulars, until at length, when
inquiries come to be made, the exact circumstances are forgotten; and
hence, multitudinous as may be such "spontaneous" variations, it is
exceedingly difficult to get at the origin of them.
The second case is one of which you may find the whole details in the
"Philosophical Transactions" for the year 1813, in a paper
communicated by Colonel Humphrey to the President of the Royal
Society,--"On a new Variety in the Breed of Sheep," giving an account
of a very remarkable breed of sheep, which at one time was well known
in the northern states of America, and which went by the name of the
Ancon or the Otter breed of sheep. In the year 1791, there was a farmer
of the name of Seth Wright in Massachusetts, who had a flock of sheep,
consisting of a ram and, I think, of some twelve or thirteen ewes. Of
this flock of ewes, one at the breeding-time bore a lamb which was
very singularly formed; it had a very long body, very short legs, and
those legs were bowed! I will tell you by-and-by how this singular
variation in the breed of sheep came to be noted, and to have the
prominence that it now has. For the present, I mention only these two
cases; but the extent of variation in the breed of animals is perfectly
obvious to any one who has studied natural history with ordinary
attention, or to any person who compares animals with others of