The Perpetuation of Living Beings, Hereditary Transmission and Variation | Page 6

animals the phenomena of asexual propagation are so obscure, that

at present we cannot be said to know much about them; but if we turn
to that mode of perpetuation which results from the sexual process,
then we find variation a perfectly constant occurrence, to a certain
extent; and, indeed, I think that a certain amount of variation from the
primitive stock is the necessary result of the method of sexual
propagation itself; for, inasmuch as the thing propagated proceeds from
two organisms of different sexes and different makes and temperaments,
and as the offspring is to be either of one sex or the other, it is quite
clear that it cannot be an exact diagonal of the two, or it would be of no
sex at all; it cannot be an exact intermediate form between that of each
of its parents--it must deviate to one side or the other. You do not find
that the male follows the precise type of the male parent, nor does the
female always inherit the precise characteristics of the mother,--there is
always a proportion of the female character in the male offspring, and
of the male character in the female offspring. That must be quite plain
to all of you who have looked at all attentively on your own children or
those of your neighbours; you will have noticed how very often it may
happen that the son shall exhibit the maternal type of character, or the
daughter possess the characteristics of the father's family. There are all
sorts of intermixtures and intermediate conditions between the two,
where complexion, or beauty, or fifty other different peculiarities
belonging to either side of the house, are reproduced in other members
of the same family. Indeed, it is sometimes to be remarked in this kind
of variation, that the variety belongs, strictly speaking, to neither of the
immediate parents; you will see a child in a family who is not like
either its father or its mother; but some old person who knew its
grandfather or grandmother, or, it may be, an uncle, or, perhaps, even a
more distant relative, will see a great similarity between the child and
one of these. In this way it constantly happens that the characteristic of
some previous member of the family comes out and is reproduced and
recognised in the most unexpected manner.
But apart from that matter of general experience, there are some cases
which put that curious mixture in a very clear light. You are aware that
the offspring of the Ass and the Horse, or rather of the he-Ass and the
Mare, is what is called a Mule; and, on the other hand, the offspring of
the Stallion and the she-Ass is what is called a 'Hinny'. I never saw one

myself; but they have been very carefully studied. Now, the curious
thing is this, that although you have the same elements in the
experiment in each case, the offspring is entirely different in character,
according as the male influence comes from the Ass or the Horse.
Where the Ass is the male, as in the case of the Mule, you find that the
head is like that of the Ass, that the ears are long, the tail is tufted at the
end, the feet are small, and the voice is an unmistakable bray; these are
all points of similarity to the Ass; but, on the other hand, the barrel of
the body and the cut of the neck are much more like those of the Mare.
Then, if you look at the Hinny,--the result of the union of the Stallion
and the she-Ass, then you find it is the Horse that has the predominance;
that the head is more like that of the Horse, the ears are shorter, the legs
coarser, and the type is altogether altered; while the voice, instead of
being a bray, is the ordinary neigh of the Horse. Here, you see, is a
most curious thing: you take exactly the same elements, Ass and Horse,
but you combine the sexes in a different manner, and the result is
modified accordingly. You have in this case, however, a result which is
not general and universal--there is usually an important preponderance,
but not always on the same side.
Here, then, is one intelligible, and, perhaps, necessary cause of
variation: the fact, that there are two sexes sharing in the production of
the offspring, and that the share taken by each is different and variable,
not only for each combination, but also for different members of the
same family.
Secondly, there is a variation, to a certain extent--though, in all
probability, the influence of this cause has been very much
exaggerated--but there is no doubt that variation is produced, to a
certain extent, by what are