The Catholic World, Vol. 10, October, 1869 to March, 1870

by Various

It is manifest that the development of rudimentary organs, with their distribution among the several varieties, is but a partial explanation of the great divergence of character. There remain to be shown, then, other processes by which this has been effected.

Divergence of character has been also caused by the development in different varieties of those parts which have been only partially suppressed under nature. This necessarily causes disproportionate development of the characters in the individuals. Proportionate development would occur if all the features of the animal or plant were subjected to equally favorable conditions, and if they were all impartially cared for by man. Convergence of character would thence result. And this convergence of character is at first sight to be expected. For if an animal or plant has, as we have seen, diverged in character under nature, and then reverts under domestication to the original perfect type, that which is to be anticipated is convergence of character. But some part presents a modification in advance of its fellows. This man seizes and makes it the peculiarity of a certain variety. By the careful conservation and judicious mating of those individuals which display a tendency to diverge in the same direction, and of those which tend least to develop new characters, he preserves the type of the variety. Modifications arising in other points of structure are similarly preserved by other breeders, and characterize other varieties. When a variety is marked by a certain peculiarity, the fancier or breeder looks with a jealous eye upon the acquisition by any individual of any new character, even though it be for the better. When, therefore, any individual of a well-established variety displays a tendency toward the production of a new character, it is systematically suppressed. "Sports" are regarded with disfavor by the fancier or breeder, and rejected as blemishes, because they tend to destroy uniformity of character among the members of the variety. Owing to these and similar causes, in each variety a different point of structure is admired, selected, and attended to, and exclusive attention given to its development, to the neglect of the others. All the features are not developed in the same variety, but are distributed among different varieties. Thus, in the carrier-pigeon the length of the beak is the character particularly attended to; in the barb, quantity of eye-wattle; and in the runt, the weight and size of the body.

In this way is effected the disproportionate development upon which divergence of character is consequent. Darwin shows this, with this difference: he believes that the modifications arise by evolution, while we contend that they arise by reversion. Nor does he concur with us in the use of the term "disproportionate development;" for that implies that the presence of all the parts in an individual is necessary to perfection. But he shows the process to be the same, be the law to which the variations conform what it may. On page 245, Vol. II., he says, "Man propagates and selects modifications for his own use and fancy, and not for the creature's own good." And on page 220 he asserts, "that whatever part or character is most valued—whether the leaves, stems, bulbs, tubers, flowers, fruit, or seed of plants, or the size, strength, fleetness, hairy covering, or intellect of animals—that character will most invariably be found to present the greatest amount of difference both in kind and degree."

Strong confirmation of this view that divergence of character is attributable to disproportionate development may be drawn from the fact that those species in which is observable the greatest divergence of character are those whose breeding is directed by fancy or fashion. Where utility guides selection, there an approximation to convergence of character is seen; but where selection is guided by fancy, there is a very strongly-marked tendency toward divergence. In the formation of varieties, fancy nowhere enters as such a predominating element as it does in the breeding of pigeons; and consequently, nowhere else is seen such great divergence. Darwin is ever directing attention to this. On page 220, Vol. I., he dwells upon it with peculiar emphasis. The converse fact is also seen. With cattle, the object of breeders is not the formation of numerous varieties, but merely the improvement of the animals. An objective mode of treatment is here identical with a subjective mode. And here we have comparatively proportionate development, and a consequent approach to convergence of character. After citing convergence of character in the case of pigs, Darwin says, (Vol. II., page 241,) "We see some degree of convergence in the similar outline of the body in well-bred cattle belonging to distinct races."

In the foregoing description of the processes of formation of domesticated varieties, we have assumed reversion as the cause of modifications. We have occasion now to speak of a process which implies a cause that is not reversion. Varieties are formed, and disproportionate development and divergence of character effected, by man's continuing the process of degeneration commenced under nature. Several illustrations of this we will adduce.

In the tumbler-pigeon, the beak is greatly reduced, and, by correlation, the feet have become of a size so small as to be barely compatible with the bird's existence. Its skull is scarce one half the size of the wild rock-pigeon, its progenitor; and the number of the vertebræ has lessened. The ribs are only seven in number, whereas the rock-pigeon has eight. The peculiarity characteristic of this variety is confessedly due to degeneration. We refer to the habit of tumbling which Darwin attributes to disease—to "an affection of the brain." (P. 153.) Other varieties of the pigeon also owe some of their characters to degeneration. In the barb, the beak is .02 of an inch shorter than in the wild rock-pigeon. Important characters have correspondingly deteriorated. Darwin, speaking of domesticated pigeons, says, "We may confidently admit that the length of the sternum, and frequently the prominence of its crest, the length of the scapula and furcula have all been reduced in size in comparison with the same parts in the rock-pigeon."

Pigs present several cases of deterioration of parts under domestication. Through protection from the climate, the coat of bristles has been greatly diminished. By disuse and man's selection, the legs have become of a size scarcely compatible with the animal's power of locomotion. Darwin requests us to "hear what an excellent judge of pigs says, 'The legs should be no longer than just to prevent the animal's belly from trailing on the ground. The leg is the least profitable portion of the hog, and we therefore require no more of it than is absolutely necessary for the support of the rest.'" Fully to realize the extreme shortness of the legs, it is necessary to see them in the possession of a highly improved breed. Correlation with the legs has led to the complete reduction of the tusks, and has induced the shortness and concavity of the front of the head which are so characteristic of domestic breeds.

With pigs, there is disproportionate development and also convergence of character. This is owing to all the breeders having aimed at the same object, the reduction of the characters given above, and the full development of the trunk or body. On page 73, Vol. I., Darwin says, "Nathusius has remarked, and the observation is an interesting one, that the peculiar form of the skull and body in the most highly cultivated races is not characteristic of any one race, but is common to all when improved up to the same standard. Thus the large-bodied, long-eared, English breeds with a convex back, and the small-bodied, short-eared Chinese breeds, with a concave back, when bred to the same state of perfection, nearly resemble each other in the form of the head and body. This result, it appears, is partly due to similar causes of change acting on the several races, and partly to man breeding the pig for one sole purpose, namely, for the greatest amount of flesh and fat; so that selection has always tended toward one and the same end. With most domestic animals, the result of selection has been divergence of character, here it has been convergence." Divergence of character is solely caused by disproportionate development, and proportionate development in all the members of the species necessarily causes convergence of character; but disproportionate development may also induce convergence, as it has done in this case.

Degeneration has also been the means of the formation of breeds of cattle, as the niata cattle, and those distinguished by the complete suppression of the horns.