Page:The Negro a menace to American civilization.djvu/84

72 varied largely, and the variations have been inherited. This has apparently been one chief cause of the belief long held by some few naturalists that species in a state of nature undergo change." It is quite a number of years ago since Darwin penned these words, and they are as true today as they were the time when they were written. All the intelligent naturalists of the present time not only believe that species in a state of nature undergo change, but they know that to be a fact. I desire the reader to ponder well upon the real significance of these facts, for a little further along I shall return to them again when I come to consider the question of their application in the case of man and the higher mammals.

When different breeds of animals are crossed, the laws of inheritance are ever in operation, and the results are seen in the morphology as well as in the traits, characters, and idiosyncrasies of the progenies of the succeeding generations. If too close interbreeding is practiced, sterility is often the result, and this condition also follows sometimes when the breeding animals have been removed from their normal habitats and food, and placed in widely different environments, climate, and subsisting upon other kinds of food. Having a sufficient number of animals to select from; and a knowledge of variability so far as we now comprehend it, with an understanding of the laws of inheritance, man can, if he chooses, produce great results. Nearly everything, however, in such experiments depends upon careful and scientific selection. Acting in this manner, we can, with greater or less certainty, produce within limits the forms we desire. If you want black cats with winning and docile natures,