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modification of organic beings as they take place asexually； or as they
may take place sexually；in either case； I say； the offspring has a
constant tendency to assume； speaking generally； the character of the
parent。 As I said just now； if you take a slip of a plant； and tend it
with care； it will eventually grow up and develop into a plant like
that from which it had sprung； and this tendency is so strong that； as
gardeners know； this mode of multiplying by means of cuttings is the
only secure mode of propagating very many varieties of plants； the
peculiarity of the primitive stock seems to be better preserved if you
propagate it by means of a slip than if you resort to the sexual mode。
Again； in experiments upon the lower animals； such as the polype； to
which I have referred； it is most extraordinary that； although cut up
into various pieces； each particular piece will grow up into the form
of the primitive stock； the head； if separated； will reproduce the body
and the tail； and if you cut off the tail； you will find that that will
reproduce the body and all the rest of the members； without in any way
deviating from the plan of the organism from which these portions have
been detached。 And so far does this go； that some experimentalists
have carefully examined the lower orders of animals；among them the
Abbe Spallanzani； who made a number of experiments upon snails and
salamanders；and have found that they might mutilate them to an
incredible extent； that you might cut off the jaw or the greater part of
the head； or the leg or the tail； and repeat the experiment several
times； perhaps； cutting off the same member again and again； and yet
each of those types would be reproduced according to the primitive
type： nature making no mistake； never putting on a fresh kind of leg； or
head； or tail； but always tending to repeat and to return to the
primitive type。
It is the same in sexual reproduction： it is a matter of perfectly
common experience； that the tendency on the part of the offspring
always is； speaking broadly； to reproduce the form of the parents。 The
proverb has it that the thistle does not bring forth grapes； so； among
ourselves； there is always a likeness； more or less marked and
distinct； between children and their parents。 That is a matter of
familiar and ordinary observation。 We notice the same thing occurring
in the cases of the domestic animalsdogs； for instance； and their
offspring。 In all these cases of propagation and perpetuation； there
seems to be a tendency in the offspring to take the characters of the
parental organisms。 To that tendency a special name is given it is
called 'Atavism'； it expresses this tendency to revert to the ancestral
type； and comes from the Latin word 'atavus'； ancestor。
Well； this 'Atavism' which I shall speak of； is； as I said before； one
of the most marked and striking tendencies of organic beings； but； side
by side with this hereditary tendency there is an equally distinct and
remarkable tendency to variation。 The tendency to reproduce the
original stock has； as it were； its limits； and side by side with it
there is a tendency to vary in certain directions； as if there were two
opposing powers working upon the organic being； one tending to take it
in a straight line； and the other tending to make it diverge from that
straight line； first to one side and then to the other。
So that you see these two tendencies need not precisely contradict one
another； as the ultimate result may not always be very remote from what
would have been the case if the line had been quite straight。
This tendency to variation is less marked in that mode of propagation
which takes place asexually； it is in that mode that the minor
characters of animal and vegetable structures are most completely
preserved。 Still； it will happen sometimes； that the gardener； when he
has planted a cutting of some favourite plant； will find； contrary to
his expectation； that the slip grows up a little different from the
primitive stockthat it produces flowers of a different colour or
make； or some deviation in one way or another。 This is what is called
the 'sporting' of plants。
In 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 parentsit 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