84 
DARWINISM 
CHAP. 
countenance, almost as varied when closely studied as that of 
a human being; not only can a shepherd distinguish every 
sheep in his flock, but we all know that each kitten in the 
successive families of our old favourite cat has a face of its 
own, with an expression and individuality distinct from all 
its brothers and sisters. Now this individual variability 
exists among all creatures whatever, which we can closely 
observe, even when the two parents are very much alike and 
have been matched in order to preserve some special breed. 
The same thing occurs in the vegetable kingdom. All plants 
raised from seed differ more or less from each other. In 
every bed of flowers or of vegetables we shall find, if we look 
closely, that there are countless small differences, in the size, 
in the mode of growth, in the shape or colour of the leaves, 
in the form, colour, or markings of the flowers, or in the size, 
form, colour, or flavour of the fruit. These differences are 
usually small, but are yet easily seen, and in their extremes 
are very considerable ; and they have this important quality, 
that they have a tendency to be reproduced, and thus by 
careful breeding any particular variation or group of varia¬ 
tions can be increased to an enormous extent—apparently to 
any extent not incompatible with the life, growth, and re¬ 
production of the plant or animal. 
The way this is done is by artificial selection, and it is 
very important to understand this process and its results. 
Suppose we have a plant with a small edible seed, and we 
want to increase the size of that seed. We grow as large a 
quantity of it as possible, and when the crop is ripe we 
carefully choose a few of the very largest seeds, or we may 
by means of a sieve sort out a quantity of the largest seeds. 
Next year we sow only these large seeds, taking care to give 
them suitable soil and manure, and the result is found to be 
that the average size of the seeds is larger than in the first 
crop, and that the largest seeds are now somewhat larger and 
more numerous. Again sowing these, we obtain a further 
slight increase of size, and in a very few years we obtain a 
greatly improved race, which will always produce larger seeds 
than the unimproved race, even if cultivated without any 
special care. In this way all our fine sorts of vegetables, 
fruits, and flowers have been obtained, all our choice breeds 
