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Darwin Correspondence Project

From Edward Blyth   8 October 1855


Octr 8th. 1855—

My dear Sir,

By the mail which leaves this day I have the pleasure to send you a copy of my printed report (just published) on a zooll. collection from the Somáli country,1 and also a lot of M.S. for your consideration.2 These you will receive through Dr. Horsfield. The said MS. consists, firstly, of 12 doz. sheets like this one, devoted to the more immediate subject of your present enquiries, which is treated more elaborately & systematically than before, in consideration of which you must pardon some repetition; & secondly, of 12 doz. more such sheets (putting your patience a little to the test, surely,) devoted to a commentary upon the 2d. Vol. of Lyell’s ‘Principles’,3 with collateral matters that occurred to me. I fancy that I have not yet quite done with Lyell, & may find time to look over his other Vols., & also certain other works, ere the next mail leaves us. With regard to the vexata quæstio of species, & notwithstanding the occasional occurrence of prolific hybrids, we still cannot but admit that, as a very general rule, species do not intermix in wild nature, as varieties of the same species (descendants from a common stock) we have every reason to think would do. Among gregarious animals however, as especially cattle, the members of the same herd well know each other, & will not readily permit an intruder from another herd to associate with them; this would help to keep varieties distinct; & then we have the fact that the most powerful male keeps other males at a distance, & so monopolizes the propagation; whereby it follows, that whilst the best blood is thus ordinarily transmitted, at the same time any peculiarity would likewise be extensively transmitted; & hence perhaps the origin of certain races, or what I have termed normal as distinguished from abnormal varieties. The influence of the same leading male might well extend over the generation of a succession of seasons, & thus permanently affect the future herd. Meanwhile, the other large males driven from the herd would mostly combat and destroy each other, or fall a prey to their natural enemies; comparatively few becoming the centres of a new circle of feminine acquaintances. On the other hand, we must remember that, in general, the male distinguished by some marked peculiarity is not the most likely one to become the patriarch of the herd! Next, it may be remarked that of species so nearly affined as to be liable to interbreed, (e.g. the humped & humpless cattle), either there are geographical difficulties to be first overcome, or, should such not present themselves, originally distinct races may have fused more or less completely long ago, & so have given origin to what have therefore come to be considered as single species, & especially to some of the more variable of our present supposed species—the Horse for instance. I could never perceive that it necessarily follows that species or races of independent origin (so far at least as one can infer this in any case) should differ at all!

In races from the most distant regions, and where we have certainly no reason to suppose that the particular species had passed from one to the other, we have every grade of approximation from the most obvious & universally acknowledged to be distinct, to undistinguishable (if not absolute) similarity. Take the Skua Gull of Australia as compared with that of the north; & this bird has never been seen within the tropics. The Great Grebes of Europe & Australia are a more doubtful case, for I have obtained the Podiceps cristatus from the Bengal Soonderbans. Or turn to Gould’s ‘Birds of Australia’. There you will find the Falcunculus of the east represented by a corresponding but obviously distinct species in the west; & many more cases of the kind. Then each principal region has its own peculiar black Cockatoo, which Gould figures as distinct;4 but the white C. galerita is common to all the regions & to N. Guinea, &c, but presents differences of size &c in different localities, indicating perhaps a plurality of races actually as distinct apart as the black one, but manifesting a still closer approximation. This is even the more likely, as we recognise the same peculiar type in the small sulphur-crested C. sulphurea of Timor, & the new C. citrino-cristata (which I have) the precise native region of which is still unknown. We can only weigh probabilities. We cannot but recognise a certain law, by which it appears that different regions (and especially those subordinate to the same zoological or botanical province) present series of species which, though admitted on all hands to be distinct & peculiar, nevertheless represent other species in the corresponding regions; the different provinces of Australia for instance; & the tropical regions E & W. of the Andes. Here we have even so remarkable a form as Rupicola represented on both sides of the chain; and numerous corresponding species of Cotinga, Tanager, &c (confining our attention to the bird class for brevity). Among such corresponding species there is every grade of approximation until all apparent distinctness is lost; & yet analogy would often indicate that such undistinguishable forms are in reality as distinct as the rest; & it is likely (I think) that not only such, but some of those corresponding races which are more or less distinguishable, would intermingle & fade were the geographical difficulties to be surmounted.— Still the phenomenon of prolific hybrids is exceptional; as remarkably shewn by my hybrids from Gallus Sonneratii; all the numerous eggs produced from or by the agency of which, with male or female of the domestic fowl, proved invariably abortive.5 Varieties of the same species we presume to be always prolific inter se: but even on this subject, consult Hutton in the ‘Calcutta Journal of Nat. History’, description of Capra ægagrus,6 which I still think is the manifest origin of the domestic Goat. It would even seem that the latter interbreeds with the Swiss Ibex, a far more different species than the ægagrus; & it is said that F. Cuvier’s figures of (or assigned to) the ægagrus, m. & f., with their young, represent these hybrid Ibices!7 But sterile individuals of pure species (both male & female) occur not so very unfrequently, and merely appear to be more common among hybrids, & among some than other hybrids. How about the Red Deer, which is said to be dying off from sterility both in Ireland and upon Dartmoor? Enquire into this. And do you remember the extraordinary case of occasional migration which occurred among the Red Deer, I think of Sutherlandshire, & of which a very interesting account was given in Chambers’s Journal? 8 Reverting to the case of affined species, no end of instances occur to me, in sundry classes, wherein it is not likely that naturalist will ever approximately come to agreement. There is the common Tree-frog of Bengal Polypedotes leucomystax., which here does not vary much, yet seems to differ in almost every district from which I have received it—various parts of S. India, Ceylon, Sylhet, Burma, Malasia, &c; in every locality there seems to be a peculiarity in the colouring. I doubt not that the Prince of Canino would make many species of it; Schlegel but one:9 & then again, surrounding this nucleus (of local varieties?), we have many other races closely affined, but more or less satisfactorily distinguishable.

Then among shells, many of the large Cyclostomata & Melaniæ of India & neighbouring countries; but, Mr. W. Clark (as I see in the ‘Zoologist’ for July last, p. 4758)10 is carrying the war into the camp of the mere conchologists! I have only quite recently seen this publication for the first time, and as yet only the Nos. for the current year: but among these I must call your attention to Dr. Knox’s remarks on species (p. 4791).11 Knox is an original thinker, and amusingly indisposed to hide his light under a bushel; moreover, not a little opinionated in some matters, & few have better grounds on which to form opinions. But I demur to his dogma about gaps (l. 10 from bottom).12 Pretty much as a tree branches off, & still divides & subdivides & resubdivides, and with almost as much irregularity, so I conceive that the successively subordinate groups of organisms divide off from each other without anastomosing or coalescing; & that accordingly there are no links connecting the twigs of the different branches, which in gardener’s phrase are never “inarched13 , but remain independent of each other save insofar as they alike ramify from one primal stem or type. Thus the principal branches represent classes, & so on.

With kindest regards, I remain | Yours ever truly, E Blyth

P.S. I meant to have said a few words about the geographic range of various wading & swimming birds; suggested by the erroneous statement in Lyell (quoted from Bewick) about that of the wild Anser cinereus.14 A considerable proportion of the waders & swimmers of the Old World have the same range as Anser cinereus; others as the Mallard & Pintail Ducks extend also to America; & the latter is very common in India, while the Mallard here keeps to the vicinity of the Himalaya. Are any save tropical Anatidæ common to the N. & S. hemispheres? I think not. The Greenshank is common to Britain & Australia, I do not admit the distinctness of glottoides. with all the intervening lands. Do. Black-tailed Godwit.

CD annotations

1.15 Among gregarious … with them; 1.17] scored brown crayon
1.25 Meanwhile … acquaintances. 1.27] scored brown crayon
1.35 Horse… at all! 1.37] double scored brown crayon
2.4 Take the … doubtful case, 2.6] double scored brown crayon
2.8 of the east … west; 2.9] heavily scored brown crayon
2.10 black … races 2.13] double scored brown crayon
2.12 to N. Guinea] ‘to New Guinea’ added pencil
2.14 black one] ‘5’ added brown crayon, circled brown crayon, del ink
2.25 Among … is lost; 2.26] scored brown crayon
2.25 corresponding species] ‘on each side of Cordillera’ interl pencil
2.28 rest;] ‘This is new argument for double creations; but only applicable to creation not to change of species’ added ink
2.31 shewn by … inter se: 2.34] double scored brown crayon
2.35 ‘Calcutta … Ibex, 2.37] double scored brown crayon
2.41 among… Dartmoor? 2.43] double scored brown crayon
2.45 of which … Journal? 2.46] scored brown crayon
2.45 Chambers’s Journal 2.46] underl brown crayon
2.48 Tree-frog … varieties?), 2.53] scored brown crayon
3.2 but, Mr… . p. 4758) 3.3] double scored brown crayon
3.5 I must … thinker, 3.6] scored brown crayon
3.9 Pretty much … & so on. 3.16] scored brown crayon; ‘Dead Branches will represent fossils & branches dead & gone those fossil & lost.—’ added ink
3.13 the twigs … each other 3.14] double scored brown crayon
5.3 that of … waders 5.4] scored brown crayon
5.6 while the Mallard … Himalaya.] heavily scored brown crayon
Top of first page: ‘4’brown crayon, circled brown crayon, del ink
Top of last page (3.2): ‘(7)’ brown crayon


Blyth 1855b. See letter from Edward Blyth, 4 August 1855, n. 2.
The two letters from Edward Blyth, [20 September or 7 October 1855] and [1–8 October 1855].
C. Lyell 1830–3, vol. 2.
Gould 1848, 2: plates 79 and 80 illustrate Falcunculus frontatus and F. leucogaster from the east and west of Australia, respectively. For the descriptions of the Australian black cockatoos, see Gould 1848, 5: plates 7–13.
CD marked this passage in Blyth’s letter (see CD annotations, above) and, on a separate slip (DAR 98: 101), wrote: This case of Gallus very good instance, in as much as G. Bankiva will cross pretty readily with Pheasant, thus Gartner right & Morton & Co quite wrong in speaking of proximate species &c. without appending the word “sexually proximate” CD refers to Karl Friedrich von Gärtner and John Chalmers Morton. Blyth’s information was used by CD in Variation 1: 234.
Hutton 1842a.
For Frédéric Cuvier’s figures of Capra ægagrus, see Jardine 1836, plates 5 and 6.
This article has not been located in Chambers’s Journal.
See letter from Edward Blyth, 7 September [1855], on the problems of defining species and the tendency of Charles Lucien Bonaparte, Prince of Canino, to make new species and that of Hermann Schlegel to regard them as varieties.
The Zoologist 13 (1855): 4758–60 contains a review of Mollusca Testacea Marium Britannicorum (London, 1855) by William Clark in which the reviewer commented: ‘we were scarcely prepared to see a dozen species dwindle into one, because, however different the shells, the animals were alike.’ (p. 4758).
R. Knox 1855, p. 4791: ‘Species are only real in so far as regards man’s observing powers: they seem to form no part of Natures scheme or plan, which obviously fills up all gaps, leaving no link deficient in the great chain… . The transmutation of one species into another I do not believe in … Unless we are prepared to adopt the doctrine of chance, there can exist only one creative idea, and consequently one creation.’
R. Knox 1855, p. 4791: ‘Those who fancy that gaps exist mistake merely a deficiency in their own knowledge for a part of Nature’s scheme.’
Inarch: ‘to graft by connecting a growing branch without separating it from its parent stock’ (OED).
C. Lyell 1830–3, 2: 101, on the geographical range of Anas anser or Anser cinereus.


Encloses two sets of notes [see 1761 and 1762]. EB believes that as a general rule species do not inter-mix in nature whereas varieties, descendants of a common stock, do. Origin of varieties. Geographically separated species are sometimes obviously distinct and sometimes apparently identical. EB does not believe that species or races of independent origin need necessarily differ. Local distribution of species of black cockatoo contrasts with the widespread white cockatoo. The occurrence of distinct but related species in different regions of a zoological province, preserved because of geographical barriers. Instances of interspecific hybrids and intraspecific sterility. Local varieties of species. Varieties are subdivisions of the main branches of the tree of organisms, dividing irregularly but remaining independent of the twigs from another branch.

Letter details

Letter no.
Edward Blyth
Charles Robert Darwin
Sent from
Source of text
DAR 98: A99–A103
Physical description
8pp †, CD note

Please cite as

Darwin Correspondence Project, “Letter no. 1760,” accessed on 26 May 2017,

Also published in The Correspondence of Charles Darwin, vol. 5