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in regard to which some additional remarks will be found towards the end of the seventh chapter.
In this third chapter an effort has been made to show that while on the Darwinian theory concordant variations are extremely improbable, yet Nature presents us with abundant examples of such; the most striking of which are, perhaps, the higher organs of sense. Also that an important influence is exercised by conditions connected with geographical distribution, but that a deeper-seated influence is at work, which is hinted at by those special tendencies in definite directions, which are the properties of certain groups. Finally, that these facts, when taken together, afford strong evidence that "Natural Selection" has not been the exclusive or predominant cause of the various organic structural peculiarities. This conclusion has also been re-enforced by the consideration of phenomena presented to us by the inorganic world.
MINUTE AND GRADUAL MODIFICATIONS.
There are difficulties as to minute modifications, even if not fortuitous.Examples of sudden and considerable modifications of different kinds. -Professor Owen's view.-Mr. Wallace.-Professor Huxley. - Objections to sudden changes.-Labyrinthodont. -Potto.-Cetacea.-As to origin of bird's wing.-Tendrils of climbing plants.-Animals once supposed to be connecting links.-Early specialization of structure.— Macrauchenia.-Glyptodon.-Sabre-toothed tiger.—Conclusion.
NOT only are there good reasons against the acceptance of the exclusive operation of "Natural Selection" as the one means of specific origination, but there are difficulties in the way of accounting for such origination by the sole action of modifications which are insignificant and minute whether fortuitous or not.
Arguments may yet be advanced in favour of the view that new species have from time to time manifested themselves with suddenness, and by modifications appearing at once (as great in degree as are those which separate Hipparion from Equus), the species remaining stable in the intervals of such modifications: by stable being meant that their variations only extend for a certain degree in various directions, like oscillations in a stable equilibrium. This is the conception of Mr. Galton, who compares the
1 "Hereditary Genius, an Inquiry into its Laws," &c. By Francis Galton, F.R.S. (London: Macmillan.)
development of species with a many facetted spheroid tumbling over from one facet, or stable equilibrium, to another. The existence of internal conditions in animals corresponding with such facets is denied by pure Darwinians, but it is contended in this work, though not in this chapter, that something may also be said for their existence.
The considerations brought forward in the last two chapters, namely, the difficulties with regard to incipient and closely similar structures respectively, together with palæontological considerations to be noticed later, appear to point strongly in the direction of sudden and considerable changes. This is notably the case as regards the young oysters already mentioned, which were taken from the shores of England and placed in the Mediterranean, and which at once altered their mode of growth and formed prominent diverging rays, like those of the proper Mediterranean oyster; as also the twenty-nine kinds of American trees, all differing from their nearest European allies similarly “leaves less toothed, buds and seeds smaller, fewer branchlets," &c. To these may be added other facts given by Mr. Darwin. Thus he says "that climate, to a certain extent, directly modifies the form of dogs."
The Rev. R. Everett found that setters at Delhi, though most carefully paired, yet had young with "nostrils more contracted, noses more pointed, size inferior, and limbs more slender." Again, cats at Mombas, on the coast of Africa, have short stiff hairs instead of fur; and a cat at Algoa Bay, when left only eight weeks at Mombas, "underwent a complete metamorphosis, having parted with its
1 "Animals and Plants under Domestication," vol. i. p. 37.
sandy-coloured fur." 1 The conditions of life seem to produce a considerable effect on horses, and instances are given by Mr. Darwin of pony breeds 2 having independently arisen in different parts of the world, possessing a certain similarity in their physical conditions. Also changes due to climate may be brought about at once in a second generation, though no appreciable modification is shown by the first. Thus "Sir Charles Lyell mentions that some Englishmen, engaged in conducting the operations of the Real del Monte Company in Mexico, carried out with them some greyhounds of the best breed to hunt the hares which abound in that country. It was found that the greyhounds could not support the fatigues of a long chase in this attenuated atmosphere, and before they could come up with their prey they lay down gasping for breath; but these same animals have produced whelps, which have grown up, and are not in the least degree incommoded by the want of density in the air, but run down the hares with as much ease as do the fleetest of their race in this country."
"Animals and Plants under Domestication," vol. i. p. 47. 2 Ibid. p. 52.
Carpenter's "Comparative Physiology," p. 987, quoted by Mr. J. J. Murphy, "Habit and Intelligence," vol. i. p. 171. Mr. Darwin, in his "Descent of Man," vol. i. p. 119, mentions that certain South American Indians (Aymaras), inhabiting a lofty region, have remarkably long bodies and short legs-especially the femora. He adds: "These men are so thoroughly acclimatized to their cold and lofty abode, that when carried down by the Spaniards to the low eastern plains, and when now tempted down by high wages to the gold-washings, they suffe a frightful rate of mortality. Nevertheless, Mr. Forbes found a few pure families which had survived during two generations; and he observed that they still inherited their characteristic peculiarities. But it was manifest, even without measurement, that these peculiarities had all decreased; and, on measurement, their bodies were found not to be so much elongated as
We have here no action of "Natural Selection; not that certain puppies happened accidentally to be capable of enduring more rarefied air, and so survived, but the offspring were directly modified by the action of surrounding conditions. Neither was the change elaborated by minute modifications in many successive generations, but appeared at once in the second.
Further, with regard to sudden alterations of form, Nathusius is said to state positively as to pigs,' that the result of common experience and of his experiments was that rich and abundant food, given during youth, tends by some direct action to make the head broader and shorter. Curious jaw appendages often characterize Normandy pigs, according to M. Eudes Deslongchamps. Richardson figures these appendages on the old "Irish greyhound pig," and they are said by Nathusius to appear occasionally in all the long-eared races. Mr. Darwin observes,2 "As no wild pigs are known to have analogous appendages, we have at present no reason to suppose that their appearance is due to reversion; and if this be so, we are forced to admit that somewhat complex, though apparently useless structures may be suddenly developed without the aid of selection." Again, "Climate directly affects the thickness
"Animals and Plants under Domestication," vol. i. p. 72. 2 Ibid. p. 76.
those of the men on the high plateau; whilst their femora had become somewhat lengthened, as had their tibiæ, but in a less degree." Here the rapidity of the change-only two generations-points rather to a direct action of conditions than to that of "Natural Selection." In favour of direct modification, another passage from Mr. Darwin may be quoted. He says, "In young persons whose heads from disease have become fixed either sideways or backways, one of the eyes has changed its position, and the bones of the skull have been modified."-Descent of Man, vol. i. p. 147.