UNIT CHARACTERS 103 
Fig. 16,’ or of an entire strain, as in cattle and pigs, and 
sometimes in a modified color, due to the absence of the 
definite pigment. 
New characters. It is much easier to understand the extinc- 
tion of characters and species than it is to account for the 
appearance of new ones; indeed, there is some reason to be- 
lieve that both the fauna and the flora of the world are getting 
simpler, that is, so far as numbers of species are concerned, by 
which is meant that, in all likelihood, species are becoming ex- 
tinct faster than new ones are appearing. 
However, new characters are appearing and, as we shall see 
later, new strains and races, equivalent for present purposes to 
new species, are constantly developing. These arise sometimes 
through the loss of a character, but often by some new combi- 
nations of old characters, resulting essentially in new races. 
Good examples of this are found in the large number of new 
strains of garden flowers, fruits, and vegetables, each with some 
distinguishing trait that is especially valuable. 
Characters and unit characters. A distinction must be here 
observed for the sake of accuracy. The term “character” is 
used in a very general sense to cover any quality or faculty of 
animal or plant to which we especially desire to allude. 
For example, we speak of the quality of milk production, 
which, as a valuable commercial consideration in cattle, may be 
roughly spoken of as a character. Upon reflection, however, it 
will be seen that it is not a «zt character, for the faculty arises 
not from a single physiological function but from several; that 
is to say, there are a variety of facts that would influence milk 
production, namely, the size of the udder, the glandular activity 
of the organ, the capacity to eat and digest large amounts of 
food, and perhaps a number of others unknown to us. 
1 Such a deer would of course have little chance of being spared either 
by the hunter or by natural enemies; hence no strain of albino deer can de- 
velop. The same is true as to albinism in bears, except in arctic regions where 
conditions are reversed. 
