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Darwin Correspondence Project

From W. H. Harvey   8 October 1860

40 Trin. Coll. Dublin

Oct. 8. 1860

My dear Sir

I have to thank you for the patience & good nature with which you have listened to my crudities, & the trouble you have taken to meet several of the points I ventured to bring to your notice— 1 I do not want to lead you into a controversial correspondence, or to be drawn into one myself, but yet there are a few matters in your letter that I would like to reply to.—

1st. — I never supposed you to say that Natural Selection could act without previous Variability. On the contrary, throughout your book Natural Selection is represented as dependent on “favourable” variations & conditions, ready to take advantage of, to perpetuate & accumulate any profitable item of differentiation;—but, in strict language, to originate nothing. Hence in my letter I have called her a Wetnurse, rather than a Mistress, & hence I can see how we may accept her as the manufacturer of multitudes of “species” (so called), such as they exist in our arrangements; and yet reject her as explaining unlimited divarications. The first impression of your book on my mind was that it too boldly assumed unlimited variability as the cornerstone of the argument; and this was the first stumbling block in my way, for I am strongly impressed with the notion (perhaps wholly wrong) that there is no law of organic or inorganic nature unlimited in its operation. And so, however widely species may vary, I suspect an oscillation in every case. In the case of your divaricating pigeons for instance, I should anticipate, after endless variations from type, either a return to type or extinction; but not the passage into a new type.

Among plants, I can believe in very wide limits of transmutation; but not equally among all plants. Orchids, Amaryllideæ, Irideæ, & perhaps most Endogens, & all Cryptogamic plants, are centrifugal in a very high degree:2—so much so that whole genera or even suborders or Orders of our arrangement may be really no more than Natural Species. Thus, for instance granting Natural Selection to be partially true, I can see how all Gramineæ may have sprung from one common parentage, one aboriginal grass (a veritable Aira præcox),—and how all Cyperaceæ, in like manner, may have sprung from one original Sedge. But here I stop, perhaps illogically, because between Gramineæ & Cyperaceæ I think there is a “saltus”, or vacant space in which it is difficult to conceive a strictly intermediate type. The difference in structure of the seed—the relation of embryo to albumen—implies opposition (or polarity) to that degree that a half & half structure must be proved to exist before I can believe in it. Now Gramineæ & Cyperaceæ are unquestionably very ancient types, if the widest distribution & great diversity of specific form be proofs of antiquity; both also must have been dominant in a high degree for myriads of years or ages,—and yet, in embryological structure, in floral arrangement, in foliation & in stem,—we have no reason for supposing that the earliest grasses or sedges respectively, were materially different from those of today. Both Orders differ from each other by an exact, definite character of seed; and in neither Order do the genera rise in organization one above the other, but in both orders the genera, so to say, stand on a dead-level or common platform of organisation. This case (and several similar might be cited) appears to me to support the notion, that natural variability has strict limits; & to bear, so far as it goes, against the notion of unlimited derivation from a Protozoon.

2d. — You regret having used the term Natural Selection, as tending to mislead, & propose Nat. Preservation as a better phrase. If you will not think it impertinent (understanding your theory so imperfectly as I do), I would suggest the term “Natural Evolution” as expressing still more exactly the idea conveyed to my mind by your theory. Do you not teach us that all organisms, past & present, have been evolved, through the action of secondary or natural laws, from one created or primæval form? If so, Natural Evolution would well express the combination of all the powers of nature in the production of species. 3d.    A word or two respecting the Ostrich’s wings.— You suppose he has lost wings, “because the whole structure of a Bird is essentially formed for flight, & the Ostrich is essentially a Bird”.3 But—if all organs ( wings included) have been gradually formed, through Nat. Sel. accumulating useful variations in successive generations;—unless the primal organism had wings & was essentially a flying animal;—then the earliest essential bird, or his remote non-bird ancestor, may have had only rudimentary wings. Now the Ostrich may be a slightly modified descendent of one of the earlier types, for his affinity to the Dinornis & other wingless birds suggests it.—   If indeed the primal-bird were formed “per saltum” or by an act of creation, the case would be different;—we should then suppose his organisation to be perfectly adapted for flight, completely furnished as a typical bird should be. But if the primal-bird ascended from a lower non-bird form, it is not at all probable that the earlier types would have been so fully furnished either with wings or with feathers as those more recently evolved. Hence, I do not see that it is “more complex” to suppose in this case an evolution, than a suppression;— when, according to your theory, the evolution must have once occurred, whereas the suppression, at best, only may have occurred. The only complexity I am guilty of is in supposing the Ostrich to represent an early type of bird, not a late one. Quere, what degree of carination of the sternum is requisite to constitute an “essential” or typical bird?—  …  . After all, I only alluded to the Ostrich to show that the facts of nature may be interpreted, by the help of your theory, in opposite ways;—that if you take one explanation, another may take the opposite, and both be equally plausible. It is a matter to me of indifference, whether the Ostrich be going up the hill or down again.

4th. — You say that I beg the question of “Protococcus being doomed to perennial similarity”.—   I own to the begging;—but pray let me state how little I here beg. Truly we know nothing of the imaginary Protozoon; but as you say you “have less difficulty in imagining the creation of an asexual cell, encreasing by simple division” than an animal of higher organisation, I hope I am not incorrect in inferring that you suppose the Protozoon to have been such a cell, so encreasing.—   Now, Protococcus nivalis is simply a spherical cell, asexual, encreasing by simple division. The sphere is also the simplest & most self-balanced form of a cell. Grant it to vary in outline however, & in size; for it does grow & has an average size when mature.— But however variable in such minor points, the structure is essentially the same in all individuals;—it is a simple, nucleated cell & no more. The question to be solved then is, how long has it remained in this condition?—   Of course, the epoch at which it was called into being is wholly undiscoverable, but for the following (theoretical) reasons I think it probable that Protococcus is very ancient indeed.—   If, as you suppose, all organisms were successively evolved from one primordial germ or Protozoon, by accumulations of useful variations from generation to generation, then it is reasonable to infer that organisms which depart least from the type of the Primordial are its nearest “blood relations”. There was an age of Protozoa before the world contained anything else, & it was probably a long period, because it must (by theory) have continued till Variability, the Struggle for Life &c &c had evolved something better. There was time for protozoic forms to diversify indefinitely, if not to exhaust all possible differentiations to which unicellular bodies could be stretched. In our times the world teems with such forms; their genera & species may be counted by thousands & tens of thousands,—& yet, these are only remnants of the innumerable lost protozoic races that preceded them. Few, comparatively, are capable of fossilisation;—but the Diatomes are, and several of the fossil Diatomes are said to be specifically identical with forms now living.— Now, it does not matter, for my argument, whether the Pre-silurian Protococcus were spherical, or oval, or square, or stellæform; or whether it were red, green or brown; it may have gone through indefinite variations of this kind, and yet I should say it was doomed to perennial similarity, if, through all changes, it remained a simple, asexual cell.—   Now, as it could not have been less complex than a cell & have retained organisation;—and as, at the present day, it is not more complex than a cell,—all I can say is that, since it was called into being, it has not materially improved in organisation. So far it has inherited “perennial similarity”; & I see no reason why it should not inherit the same to the end of the world.—   But, you may say, why should Protococcus & similar organisms, be regarded as relics of a Protozoic, pre-silurian world & not modern organisations?— I reply:—either they must have come down to us as undivaricated protozoa, from your Protozoon by uninterrupted succession of generation;—or, they must represent higher animals & plants which once flourished, but which through gradual loss of organs from disuse, & a continual struggle with adverse circumstances, have dwindled down to a monadic condition;—or, they must have been spontaneously generated, from age to age, that is to say, the creative act of calling a living cell from the dust, must have been repeated an infinite number of times from the dawn of life to the present day.—   I can find no other way of accounting for their existence; & I suppose your theory would prefer the first supposition, as the simplest—that they have lived, as Protozoa, from the dawn of life to the present day.—

And here I would observe, that if you maintain that Protozoic organisms now living are lineal descendents of the aboriginal Protozoon;—and if you also maintain that all higher animals & plants have descended (or rather ascended) from the same aboriginal Protozoon, through the agency of natural laws alone, without the personal interference of an Intelligent First Cause,—you are bound to show theoretically how such widely different results have been arrived at. At starting we have similar elementary organisms, under similar conditions of life, all exposed to the same struggle, all subjected to similar “laws acting round them”. Why have some remained Protozoa to the present day, while others have developed into Whales or into Man?—   Have the “perennially similar” races had no struggle for life? I suppose not, for they have remained perennially similar. But what kept them out of the struggle while all around them, of their own kind & in their own condition as respects outward circumstances were wriggling upward into higher beings? And what set these latter in motion? A struggle for life. Side by side, in the same sea, with the same water to swim in, the same food to eat, the same sun above them; one Protozoon remained in statu quo unexterminated, another advanced in organisation & developed nerves, sinews & bones; one perhaps was drawn into an eddy & so swam round & round forever; the other floated on a current & gradually drifted into a new phase of being.—

5th— You dissent from my requiring myriads of years to overstock the Earth with the imaginary Protozoon & refer to Ehrenberg’s calculation of the time it would take for an infusorium to make a cube of rock.4 The time required will depend on the nature of the protozoon. If it secreted lime, like one of the Foraminifera, or silex, like a Diatome, its dead shells would rapidly form strata; but if it were like a Protococcus or an Amoeba no such result could follow for infinite ages. But my argument had reference to something more than a question of time;—I wished to show the difficulty of eliminating a struggle for life, of inducing variation, & leading, through Nat. Selection, to the evolution of higher animals from a protozoon, so placed in a universal sea.—

Granting however that it secreted lime, like a Foraminifer, & rapidly propagated itself: what would result?—   I see nothing at first but a thin film of chalk spread out over the bottom of the ocean, & gradually encreasing in thickness till the sea became shallower & shallower, until (supposing lime enough) it was filled up at last;—all which filling up must have occurred before the struggle for life commenced, for so long as clear water & available lime remained the Protozoon (if analogous to his modern kindred) had all he required. And, as the available lime diminished, though the newer generations might have thinner & thinner shells, & might at last come to be membrane coated or gelatinous, they need not have made a single onward step;—& the fact of their contriving to do without lime would still further retard the struggle for life, for they would have fewer wants to supply, their debris would more slowly accumulate & the clear water would be less rapidly filled up. Suppose however that the lime diminished unequally, & that, in some favoured localities the lime-secreting species continued to propagate;—though you might then have two species “naturally selected” where but one had been before, yet the newer might be the lower & feebler type, for the power of secreting lime would be lost, by disuse, & with it whatever apparatus was fitted to that purpose. We may indeed suppose that the power of secreting might remain & be diverted to the secretion of silex or any other earth; and so we should get a third, or more species.—   To this I have nothing to object;—all these & similar “specific” changes are compassable by Natural Selection. But it is yet to be shown whether all such adaptations to circumstances have not, in every case, their natural limits. We can conceive a Protozoic world so originating & becoming greatly varied in “species” without one of them rising sensibly in organisation above another. Like snow-crystals their patterns may be innumerable, but their organisation all of a piece. The modern Protococcus may be very unlike the imaginary Protozoon in outward form & in habits of life, and yet, in simplicity of organisation, it may be identical;—each a nucleated, asexual, spontaneously dividing cell.

The arguments above applied to an imaginary protozoon appear to me to fit as well in the case of a reefbuilding coral;—and if Agassiz observations on the reefs of Florida may be depended upon, namely, that there is no difference in species between the bottom & top of a long persisting reef,5 it further illustrates the “perennial similarity” of low forms for indefinite periods.

6th. — A word or two more about Variability.6 I fear, by your referring me back to passages in the Origin where Variability is insisted on, you have misunderstood what I meant, when, in my letter, speaking of Unknown Laws of Variation, I say:—“If therefore these are necessary, at starting, to set Natural Selection in motion, we are surely calling up a wholly different Agency to any set forth in your Theory” &c. I did not mean that you had ignored such Laws, for at the opening of Chap. 5, in speaking of them, you pointedly say that they are not due to chance, but to an unknown cause. What I meant was that, to variation from this Unknown Cause, & not to “Variability from the indirect & direct action of the external conditions of life, from use & disuse” (p 490) we must, in the present state of science, attribute all the Major divarications of the organic world, even on the theory of evolution from a primordial. We must, I think, draw a broad line between Variations arising from allied conditions of life, from use & disuse, and those Variations that introduce new stages of being, molding an animal body with symmetry of limbs & definite position of internal organs; that, early in the history of life, introduced a definite number of typical formulæ (radiate, articulate, molluscoid, vertebrate, &c), & have retained these same types, through every change of outward circumstances, to the present day.—   Variations arising from altered conditions &c, being impersonal, may fairly be referred to secondary causes;—but the other & infinitely the larger class of unresolved Variations, including Correlation of Organs or modelling after a preconceived pattern, imply personality, & therefore (to avoid pantheism), I ascribe them to the Creator. Natural Evolution, no doubt, takes advantage of every such organic change & commences a new set of modifications upon it, but (as I think) is insufficient to explain or originate it. These steps (however originated), and however small in amount each may be, are the saltations for which I have all along been contending,—the non-recognition of which, in the theory of Natural Selection, appears to me like leaving out the keystone of the arch.

But it is useless to carry on the discussion. I must again apologise for my prolixity, & remain,

My dear Sir | very truly yours | W. H. Harvey

Charles Darwin Esq, FRS. | &c &c

CD annotations

2.2 On the … conditions, 2.3] cross added pencil
2.8 The first … argument; 2.10] two crosses added pencil
3.8 But … space 3.9] cross added pencil
3.13 Now … Protozoon. 3.23] scored pencil
4.5 Do you … form? 4.6] cross added pencil
5.7 Now … it.— 5.8] cross added pencil
5.17 The only … one. 5.18] cross added pencil
7.4 without … at. 7.6] cross added pencil
8.1 You … rock. 8.3] cross added pencil
11.8 What … world, 11.11] scored pencil; ‘6 fingered man— hard to say if indirect cause of conditions’ added pencil
Verso of last page: ‘Harvey’ brown crayon; ‘Dominant Forms | Struggle for Existence | Antiquity of World &c’ pencil


The expression ‘centrifugal’ variation was coined by Joseph Dalton Hooker to represent changes that made the organism diverge from the parental type. See Hooker 1844–7, p. 315, and Correspondence vol. 7, letter from Charles Lyell, 28 October 1859 and n. 4. Harvey and Hooker were close friends.
Ehrenberg 1854–6, pp. viii–ix. See letter to W. H. Harvey, [20–4 September 1860].
Agassiz 1851b.
Harvey apparently enclosed with the letter a pamphlet that addressed some of the same points about variability. The pamphlet gave the text of a lecture delivered at the Dublin University Zoological and Botanical Association on 17 February 1860 (Harvey 1860). It is in the Darwin Pamphlet Collection–CUL, marked ‘With the writers repentance. Oct. 1860.’ In it Harvey stated: ‘It strikes me that there is fallacy at the very base of Mr. Darwin’s argument; and that his whole superstructure rests on the assumption that Variability acts indefinitely and continuously, without check or hindrance.’ An annotation by CD on the back cover relating to this passage states: ‘Preface—good to admit that continued variation is an assumption’.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Harvey, William Henry. 1860. An inquiry into the probable origin of the human animal, on the principles of Mr Darwin’s theory of natural selection, and in opposition to the Lamarckian notion of a monkey parentage. Dublin: privately printed.

Hooker, Joseph Dalton. 1844–7. Flora Antarctica. 1 vol. and 1 vol. of plates. Pt 1 of The botany of the Antarctic voyage of HM discovery ships Erebus and Terror in the years 1839–1843, under the command of Captain Sir James Clark Ross. London: Reeve Brothers.


Thanks CD for his patience and good-nature; does not want a controversial correspondence but wishes to reply to matters in CD’s letter, and does.

Letter details

Letter no.
William Henry Harvey
Charles Robert Darwin
Sent from
Trinity College, Dublin
Source of text
DAR 98 (ser. 2): 54–7
Physical description
ALS 7pp †

Please cite as

Darwin Correspondence Project, “Letter no. 2943,” accessed on 27 March 2023,

Also published in The Correspondence of Charles Darwin, vol. 8