Difficulties of the Theory of Natural Selection. II. WE continue, in the following pages, to discuss some of the heads of objections which we have already indicated to Mr. Darwin's theory. 3. That there are grounds for thinking that specific differences may be developed suddenly instead of gradually. The difficulty of comprehending the preservation of infinitesimally small beginnings of useful structures (considered in the first part of this paper), together with the absence of certain fossil forms (to be considered later), appear to us to point in this direction. Some facts however brought forward in Mr. Darwin's last work appear decidedly to harmonise with a rapid development of specific differences. Such facts are 1. "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;") 2. that cats at Monbas, on the coast of Africa, have short stiff hairs instead of fur, and that a cat at Algoa Bay when left only eight weeks at Monbas "underwent a complete metamorphosis, having parted with its sandy coloured fur;"+ 3. that the conditions of life seem to produce a considerable effect on horses, and instances are given of pony breeds having independently arisen in different parts of the world, possessing a certain similarity in their physical conditions; 4. that as to pigs, so Nathusius § states positively as the result of common experience and of his experiments-rich and abundant food, given during youth, tends by some direct action to make the head broader and shorter, and vice versa; 5. that curious jaw appendages often characterise Normandy pigs, according to M. Eudes Deslongchamps. Richardson figures them on the old "Irish greyhound pig," and they are said by Nathusius to appear occasionally in *Animals and Plants under Domestication, vol. i., p. 37. all the long-eared races. Mr. Darwin observes,* "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;" 6. that "climate directly affects the thickness of the skin and hair" + of cattle; 7. that in the English climate an individual Porto Santo rabbit recovered the proper colour of its fur in rather less than four years; 8. that the effect of the climate of India on the turkey is considerable. Mr. Blyth § describes it as being much degenerate in size, "utterly incapable of rising on the wing," of a black colour, and "with long pendulous appendages over the beak enormously developed;" 9. that among other curious instances of the direct effect of conditions on individual animals may be selected that given by Mr. Darwin from M. Costa, || who has recorded of oysters, "that young shells, taken from the shores of England and placed in the Mediterranean, at once altered their manner of growth, and formed prominent diverging rays, like those on the shells of the proper Mediterranean oyster;" 10. that, as Mr. Meehan,¶ quoted by Mr. Darwin** tells us, twenty-nine kinds of American trees all differ from their nearest European allies in a similar manner—“leaves less toothed, buds and seeds smaller, fewer branchlets," &c.; 11. that there has suddenly appeared in a bed of common broccoli a peculiar variety faithfully transmitting its newly acquired and remarkable characters; 12. that there has been a rapid transformation and transplantation of American varieties of maize into a European variety; 13. that certainty "the Ancon and Manchamp breeds of sheep," and that all but certainly "Niata cattle, turnspit and pug-dogs, jumper and frizzled fowls, short-faced tumbler pigeons, hooked-billed ducks, &c., and a multitude of vegetable varieties, have suddenly appeared in nearly the same state as we now see them."§§ Lastly-a most significant fact-that there has been an occasional development (in five distinct cases) in England of the "japanned" or "black-shouldered peacock." Pavo nigri *Animals and Plants under Domestication, vol. i., p. 76. Ibid., p. 91. Ibid., p. 114. $ Quoted Ibid., p. 294. Bull. de la Soc. Imp. d'Acclimat, tom. viii., p. 351. Quoted by Mr. Darwin in vol. ii., p. 280. ¶ Pro Acad. Nat. Sc. of Philad., Jan. 28, 1862. ** Ibid., p. 281. ++ Animals and Plants under Domestication, vol. i., p. 324. Ibid., vol. i., p. 322. SS Ibid., vol. ii., p. 414. pennis, a distinct species, according to Dr. Sclater, yet arising. in Sir J. Trevelyan's flock, composed entirely of the common kind, and increasing, "to the extinction of the previously existing breed." + Mr. Darwin's only explanation of the phenomenon. (on the supposition of the species being distinct) is by reversion, owing to a supposed ancestral cross. But he candidly admits: "I have heard of no other such case in the animal or vegetable kingdom." On the supposition of its being only a variety he observes: "The case is the most remarkable ever recorded of the abrupt appearance of a new form, which so closely resembles the true species, that it has deceived one of the most experienced of living ornithologists." After these facts it is somewhat startling to meet with the dogmatic assertion, that it is a false belief that natural species have often originated in the same abrupt manner. 4. That the causes of variability in domestic animals have not been proved to be of the same nature as those acting upon wild species. The much greater degree of variation. among domestic animals than among wild ones is asserted over and over again by Mr. Darwin, and the assertions are supported by an overwhelming mass of facts and instances. These remarkable variations extend to instincts and propensities as well as to ascertainable points of structure. No individual wild animal has ever been found living under sexual relations opposed to those adopted by the rest of its species. Nevertheless, the wild drake is monogamous while the domestic one has a polygamous habit. § Again it is demonstrated by Mr. Darwin's careful weighings and measurements, that, though little used parts in domestic animals get reduced in weight and somewhat in size, yet that they show no inclination to become truly "rudimentary structures." Accordingly he asserts || that such rudimentary parts are formed "suddenly, by arrest of development" in domesticated animals, but in wild animals slowly. The latter assertion, *Proc. Zoo. Sc. of London., Ap. 24, 1860. + Animals and Plants under Domestication, vol. i., p. 291. We may remind our readers that certain axolotls (large Mexican efts with permanent gills) have quite unexpectedly put on what is believed to be the normal adult form of the species. Only a few have done so, but these have done it completely and suddenly. § Animals and Plants under Domestication, vol. ii., p. 304. || Ibid., p. 318. however, is a mere assertion; necessary indeed for the theory of "Natural Selection," but in no other way. Of course it may be asserted that a tendency to indefinite variability exists equally in all cases, and that it is the circumstances and conditions of life alone, which cause the effects of this common tendency to differ so much in the two cases. But assertion is not proof, and this assertion cannot be proved. Indeed it may equally be asserted (and we think it is a statement more consonant with the above facts) that domestication in certain animals induces and occasions a tendency to vary which is absolutely wanting in wild animals-the introduction of new causes occasioning new effects. For, though a certain minute variability (or rather oscillation) exists in all organisms, yet domesticated ones are exposed to new and different causes of variability, resulting in such striking divergencies as have been observed. Not even in this latter case however is it necessary to believe that the variability is indefinite, but only that the small oscillations become in certain instances intensified into large and conspicuous ones, Moreover, it is possible that our domestic animals have in part been chosen and domesticated through possessing a capacity for variation in an eminent degree; and this brings us to the fifth consideration. 5. That there is more reason to believe that species have definite limits to their variability, than that all are capable of indefinite variation. This proposition is largely supported by facts brought forward by the zealous industry of Mr. Darwin himself. It is unquestionable that the degrees of variation which have been arrived at in domestic animals have been attained more or less readily in a moderate amount of time, but that further development in certain desired directions is in some a matter of extreme difficulty, and in others of absolute impossibility. It is also unquestionable that the degree of divergence attained in one domestic species is no criterion of the amount of divergence which may be produced in another. It has been contended on the other hand--(1.) That we have no evidence of any limits to variation other than what are imposed by physical conditions, such, eg, as those which determine the greatest degree of speed possible to any animal (of a given size) moving over the earth's surface; (2.) that the differences in degree of variation presented by different domestic animals are due to the varying direction and amount of attention in man's selection, combined with abundance or scarcity of individuals; (3.) and finally, that |