generates of different origin—a similarity that permits us to make a classification the scale of which is as a whole narrow enough, has been reproduced in experiments having the provocation of artificial monsters as their object. If the incubation of hen's eggs is disturbed by eccentricities of temperature, if they are warmed too much or not enough, if they are deprived of air, if poisonous substances or substances capable of modifying the nutrition of the embryo—ether, chloroform, alcohol, essences, or nicotine—are introduced into the medium in which they respire, if the same substances are caused to penetrate into the albumen, if they are shaken by abrupt shocks or feeble but repeated blows, monstrosities are generally produced; but it does not appear that any of these causes will provoke exclusively the formation of a special monstrosity. Each of these causes will produce a variety of deformities, any of which may resemble other deformities produced by other causes. In short, the general facts already noticed in degenerating descent may be found in hatches experimentally disturbed—unlikeness in the same families and resemblance of unlike types of one family with those of another.
Besides resulting in ultimate sterility, morbid heredity and degeneration contribute to the destruction of families and races by producing mental and moral differences among them that lead to dissensions and conflicts as mischievous as diseases. When multiple crossings of normal individuals have been effected in a single locality or country, they create in the end both physical resemblances—a family air, a national type—and also psychical likenesses, which entrain a community of tastes and consequently of moral ideas susceptible of becoming fixed for a long series of generations and of constituting a family or national character. The dissolution of heredity, which may be realized either by the introduction of strangers of too different races, or under the influence of native causes of degeneration, is marked both by physical unlikenesses and by the psychical and moral ones that necessarily accompany them. The social discords that spring up among a people like those that so often divide the families of degenerates, taken together, constitute a manifestation of the dissolution of heredity; their source is in a biological fact.
The facts that authorize us to regard morbid heredity or degeneration in general as the consequence of disorders of nutrition during the developmental period of evolution permit us to comprehend the exceptions to the laws of heredity, and consequently to conceive the possibility of securing means of favoring these exceptions and of contending against degeneration.
A strong temptation arises to propose a law prohibiting the marriage of certain categories of degenerates, whereby the natural
