TRANSACTIONS OF SECTION D, 771 
Heredity, 
Having now spoken at some length of the phenomenon of variation, I must 
i. to consider from the same general point of view the phenomenon ot 
eredity. 
As We have seen, in asexual reproduction heredity appears, as a general rule, 
if not always, to be complete. The offspring do not merely present resemblances 
to the parent—they are identical with it. And this fact does not appear to be 
astonishing when we consider the real nature of the process, Asexual reproduc- 
tion consists in the separation off of a portion of the parent, which, like the parent, 
is endowed with the power of growth. In virtue of this property it will assume, 
if it does not already possess it, and if the conditions are approximately similar, 
the exact form of the parent. It is a portion of the parent; it is endowed with 
the same property of growth; the wonder would be if it assumed any other 
form than that of the parent. Indeed, it is doubtful if the word ‘heredity ’ would 
ever have been invented if the only form of increase of organisms was the asexual 
one, because, there being no variation to contrast with it, it would not have struck 
us as a quality needing a name, any more than we have a name for that property 
of the number two which causes it to make four when duplicated. 
The need for the word ‘heredity’ only becomes apparent when we consider that 
other form of reproduction in which the real act of reproduction is associated with 
the act of conjugation. Looking at reproduction from a broad point of view, we 
may sum up the difference between the two kinds, the sexual and the asexual, by 
saying that whereas the essence of sexual reproduction is the formation of a new 
individuality, asexual reproduction merely consists in increasing the number of one 
kind of individual. From this point of view sexual reproduction is better termed 
the creation of a new individuality, for that, and-not the increase in the number 
of individuals, is its real result. Inasmuch as conjugation of two organisms is the 
essential feature of sexual reproduction, it would appear that the number of 
individuals would be actually diminished as a result of it; and this does really 
happen, though in a masked manner, for we are not in the habit of looking upon 
the spermatozoon and ovum as individuals, though it is absurd not to do so, as they 
contain latent all the properties of the species, and are sometimes able to manifest 
these properties (parthenogenetic ova) without conjugating. In some of the lower 
organisms the fact that conjugation does not result in an increase of the number of 
individuals, but only in the production of a new individuality, is quite apparent, 
for in them two of the ordinary individuals of the species fuse to form one (many 
Protozoa). 
So that sexual reproduction gives us a new individuality which can spread to 
almost any extent by asexual reproduction. This asexual reproduction gives us a 
group of organisms which is quite different from a group of organisms produced by 
sexual reproduction. Whereas the latter groups constitute what we call species, 
the former group has, so far as I know, no special name, unless it be variety ; but 
variety is not a satisfactory name, for it has been used in another sense by 
systematisers. 
Heredity, then, is really applicable only to the appearance in a zygote of some 
of the properties of the gametes. A zygote has this property of one of the prece- 
dent gametes, and that property of the other, in virtue of the operation of what we 
call heredity ; it has a third property possessed by neither of the precedent gametes 
in virtue of the action of variation, the nature of which we have already examined. 
It is impossible to say which property of a gamete will be inherited, and it is 
impossible to predict what odd property will result from the combination of the 
properties of the two gametes. Of one thing only are we certain, that they are 
never the same in zygotes formed by gametes produced in immediate succession 
from the same parent. 
We may thus regard the activities of the zygote as the resultant of the dashing 
together of the activities of the gametes. 
Conjugation, then, is a process of the utmost importance in Biology; it pro- 
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