‘Please give my kind regards to your family. “‘ Yours sincerely,

‘‘H. W. BATES.

«Will you please give me the reference to your remarks on colours of plants, and fur of arctic animals, not being dependent on climate? I must quote you in my book where I have given similar generalisation.’’

7c ee, dionker, 10.17. 1%... bates.

“My DEAR MR. BATES, ‘““KEw, March 18th, 1862.

‘*T have asked Mr. Bentham about the names of the Sprucean plants, but he has unfortunately kept no list of the native names; they are

scattered through the herbarium in their natural orders, which is scarcely according to a native’s notions. That of the cow-tree he remembers as a species of sapotaciz, without flowers or fruit, and therefore indeterminable. In answer to your long and full-of-interest letter, 1 have rather an absurd request to make—that you would return me my last if you have not destroyed it. I have almost forgotten its tenor; and Mr. Darwin, who is extremely interested in yours, has asked me and you to let him see mine to you, when, if you care for it, it shall be returned to you forthwith. ‘‘True, as you say, it #zay be that ‘ characters acquired through the action of local conditions’ are propagated. I grant that my antagonistic position to this view is not based on any good foundation; to tell you the truth it rests, as a Jr7nciple, very much on an inherent prejudice in my mind against attributing one natural phenomenon to the operation of two distinct laws or operations of nature. If variation will do it all, and you allow variation to accumulate ad lzbztum, why call up any other frz7e cause? and complicate unnecessarily what otherwise is a very simple rationaie, however inexplicable, until, at any rate, some clear case of such propagation of z7dwzced character is brought forward. I am quite aware that this is a very unsatisfactory answer, and you know that I do not hold the original proposition as an irrefragable truth, and only say I am prone to believe that way. There is a great deal in what you say as to use and disuse, and this I grant is a very formidable argument against the position I adopt. It does apparently stand to reason that organs present, but not used, should atrophy; but this does not demand the propagation of the atrophied state acquired by the individual. A.g., say that organ ‘little finger’ falls out of use—it is no longer then a matter of indifference to you whether it is present or no; if present and not in use it #wst be in the way, therefore be prejudicial. Therefore, amongst the variously developed fingers of the progeny, those individuals will be preserved which have smallest little fingers, and so on ad extinction. The male nipple shows how little mere disuse has to do with the abolition of an organ, so long as it is not in the way. Your case of the races of man inhabiting tropics of America and Africa is a most remarkable and interesting one. Again, your observation that ‘ local physical conditions do not directly produce a race,’ is a pregnant one— ‘a dozen different varieties in a single spot’ is a wonderful fact, and gives a deep insight into the laboratory of Nature. Your expression of natural selection ‘drawing out’ the varieties, is a happy one. 1 do not remember Darwin using it. ‘‘ Have you read Asa Gray’s review, etc., of Darwin? If not I can lend you them. He had one exquisite illustration of little streams guided by the finger to form a great river. I forget it exactly.

‘The moral barrier checking frequent intermarriages no doubt plays a great part; in other words, ‘ physiological obstacles’ are great. These first, perhaps, lead to forms taking separate geographical areas, and hence being brought into contact with other forms, just as children of a family centrifugate from the parental house, and as a rule do not marry their cousins and blood relations—not out of any social or moral obstacle, but in obedience to the centrifugal tendency.

‘Your instance of the woolly sheep hits me hard; itis the very fact of this undoubted influence of conditions over zzdumentum that puzzles me above all others. It is inconceivable at first sight that a sheep, however woolly when transported to a climate which causes all wool to vanish, should have a breed of lambs as well woolled as those of a cold climate, but it is possible. I quite understand the climate bringing on a change in the skin of the individual sheep, and influencing growth of hair, which is only an appendage of the skin; but I find it hard to believe that this change wrought on individuals should be directly propagated. Lop-eared rabbits are, I think, pure cases of artificial selection; of dogs I know not, but should suspect it too, as we have thousands of breeds of prick-eared dogs who do not want their ears more than the lop-eared do. T do not think I have anywhere published any notices of colours of plants in relation to climate, but I will see and let you know. I think I have somewhere noticed woolly plants not being more arctic than tropical, and will hunt up reference. ‘‘One more point in connection with disuse of organ. In all these cases the loss of an organ must be counterbalanced by increased activity of other or others, and the #azerza/ used for lost organ is diverted to others; so here natural selection comes doubly into play, not only selecting individuals in which the disused organs are small, but those in which the szaZerial goes in a desired direction. ‘ Fleshiness of plants on sea coast is a case I am disposed to attribute to direct influence of conditions; wet and succulence go together so naturally that it is difficult to conceive of these not being cause and effect, and we have it displayed in every way everywhere. But then, fatness of general tissues, like large leaves, flowers, fruit, etc., etc., hardly come under same category as variation of form, etc., though it is hard (impossible?) to separate them philosophically. ‘With regard to colour of negro being ‘ due to direct action, and also being best suited to climate,’ do not forget that the Tasmanian was awfully black, ditto the Fuegian, and the New Zealanders and Eskimaux both very dark. It has always struck me as odd that man is the only animal that blackens in tropics; if this was an affair of direct action of sun, why are no other animals black in tropics? ‘ Ever yours,

**** FxDS HOOKER.”**

Hl. W. Bates to Dr. J. D. Hooker.

‘““ KING STREET, LEICESTER, March 21st, 1862.

**MY DEAR SIR,

‘* Many thanks for the trouble you have taken in determining the nature of the clothing on the underside of the leaves sent. It is a pity I did not get the flower or fruit of the tree. ** All the leaves of the tree did not possess the wool. Is it to be considered an excretion of the leaves or natural clothing of them, or a foreign substance? ‘* Please keep the box until next journey to town. *‘T think I said in my last that I had not finished answering your very important letter. In fact mine was not a close answer to it at all, which you

and Mr. Darwin will see on reading yours. There is no new view in my line of argument—it is the same as Mr. Darwin’s. There is no irreconcilable difference, I think, between your view and his, but Mr. Darwin’s seems to harmonise best with the facts of variation as gleaned from the distribution of closely-allied species and varieties of insects which have come under my notice. ‘‘We all agree that variation exists in nature as a general, perhaps a universal, rule. In other words, children are never exactly like each other or their parents. Also that natural selection must act, probably on the first, surely on an early subsequent generation of a species when it has entered under new conditions. ‘* This is a logical necessity arising from excessive increase and struggle for existence. The only debatable point is: do external causes, food and climate, influence variation, or is variation a universal condition of reproduction, and totally independent of external causes? ‘«Mr. Darwin, as I glean from his book, supposes external causes to act in three ways:—1. By disturbing the reproductive system of the parents, and thereby inducing variability. 2. By promoting use or disuse of organs.. 3- By acting directly on the constitution in a general or special way. The modes of action 2 and 3 of course would be without result if the acquired modifications were not transmitted to the offspring. The variations produced by No. 1 may be considered as not traceable to the dzvect action of external conditions on the parents, as those would be which are due to Nos. 2 and 3. ‘“‘T think your tendency of opinion is towards the view that variation is not brought about, or not at all affected, by any of these three modes. You look upon it as a universal condition of reproduction, and compare it as a law with gravitation. It is a grand, simple, and beautiful conception. I wish it would prove true. I am quite surprised to find how well it suits many facts of the apparent formation of new races in nature. I think of it every day in poring over my long series of varieties of South American insects, which are all carefully ticketed with localities, and have a history to me as being all taken and observed by myself; I apply your view and find it to suit well in many cases. I have suites of specimens showing the formation of three or more distinct races out of one species, and others exhibiting the same process half-completed,—z.e., the races are imperfectly segregated, all the intermediate gradations existing,—and after repeated examination and long reflection, I really do not see the necessity of calling in the action of food or climate to explain the process. The local conditions are more favourable to certain variations than others; these live and multiply, the intermediates are extinguished. A strong preference of exact counterparts to pair with, and the rarity of intermediate grades rendering possible the segregation of races—two or more in one locality—though perhaps when the distinct ones were formed they were separated by some geographical barrier;perhaps a slight and unapparent one. Nevertheless some facts go to prove that all these three modes of operation do prevail. In support of No. 1 comes the important fact so prominently brought forward by Mr. Darwin, that the reproductive functions are greatly disturbed when a wild species is brought under confinement or cultivation. I have distinct proofs from nature that a species is tolerably constant in one localityand very inconstant in another; nay more, exhibiting a tendency to

segregate one or more distinct races out of its varieties in a third. These facts seem to establish principle No. 1, and I should think domestication and cultivation furnish many others.

‘With regard to No. 2, Mr. Darwin quotes numerous instances, but generally with the qualifying suggestion that selection comes into play in almost every case. As natural selection is a/ways and of zecesszty in action, and the growth or atrophy of an organ a slow process requiring an immense number of generations to show conspicuous results, it must be impossible to disentangle the two principles in these cases. We should require to be shown (as you insist upon in other cases) a distinct case of growth or atrophy produced in a lifetime and transmitted to children. But any important degree of these requires many successive generations, and then, as in blind ‘animals in caves, natural selection must come into play. ‘‘ The same remarks apply to No. 3; but we have distinct facts to prove the propagation of acquired peculiarities. 1 think the fact of hereditary diseases proves a great deal, although you treat it slightly. It is true that a diseased species could not exist in nature. This is no matter; the fact remains that a peculiarity acquired in the lifetime of a parent is transmissible to its offspring. ‘*T hope you will excuse my objecting to your conclusions regarding shaving and circumcision. These are slight mzutz/ations which seem, a priori, unlikely to be heritable: acquired modifications of the circulating fluids, which affect the skin, its clothing and colours, the glandular system, etc., etc., seem more likely to be transmissible to descendants. The action of climate, food, and habits on the individual during lifetime is, of course, undeniably great. So obvious is it that all naturalists have attributed local varieties to it. That a local variety has ever been formed solely by it I hold to be exceedingly improbable for the same reasons as above mentioned, namely, that it would take a great number of generations, and during the process natural selection wzwzs¢t come into play.

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