180 ESSAYS. 
fertilization in the species, either constantly or occasionally, 
which are so general, so varied and diverse, and we may add 
so exquisite and wonderful, that, once propounded, we see 
that it must be true. What else, indeed, is the meaning and 
use of sexual reproduction? Not simply increase in num- 
bers ; for that is otherwise effectually provided for by bud- 
ding propagation in plants and many of the lower animals. 
There are plants, indeed, of the lower sort, in which the whole 
multiplication takes place in this way, and with great rapidity. 
These also have sexual reproduction ; but in it two old indi- 
viduals are always destroyed to make a single new one! Here 
propagation diminishes the number of individuals fifty per 
cent. Who can suppose that such a costly process as this, 
and that all the exquisite arrangements for cross-fertilization 
in hermaphrodite plants, do not subserve some most important 
purpose? How and why the union of two organisms, or 
generally of two very minute portions of them, should rein- 
force vitality, we do not know and can hardly conjecture. 
But this must be the meaning of sexual reproduction. 
The conclusion of the matter from the scientific point of 
view is, that sexually propagated varieties, or races, although 
liable to disappear through change, need not be expected to 
wear out, and there is no proof that they do; but that non- 
sexually propagated varieties, though not liable to change, 
may theoretically be expected to wear out, but to be a very 
long time about it. 
