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Darwin Correspondence Project

From Albert Günther   [before 27 September 1869]1

1. I have described Mollienesia petenensis with a dorsal fin ornamented with ‘a row of large rounded spots’ because this is sufficient for specific description.2 Ichthyologists rarely describe bright-colored ornamentations, because they are most subject to variation as regards form, number intensity & color (what is blue in one individual, may be green or even red in another, as in many Labridæ),3 & because they disappear or change in spirit, & therefore, are of no specific value. I perfectly recollect that, when I received the examples of Moll., spots of dark & bright (bluish) colors were mixed; after the specimens had been in spirit for some time, the bright shades disappeared, & now I could not exactly state their distribution. The large round spots may have been dark, blackish, or violet; this I cannot decide; but they were certainly surrounded by a lighter ring (true ocelli), as it is also indicated in the figure.4

2/ I have also heard that certain American Chromids sit on a nest, but I do not know which sex; nor do I recollect that any exact observations have been published about this.5 Knowing several American Ichthyologists, shall I write to one of them?

3. Since I saw you last, I have subjected Solenostoma to a careful examination. We have about a dozen females of about the size of the specimens figured in the Fish. of Zanzibar, & one male only, of about 13 the size of the females.6

a./ It may be concluded from this disproportion of male & female specimens, either that males are scarcer than females, or that males always are of much smaller size than females. I am inclined to believe the latter, because of those Cyprinodonts7 in which the male is much inferior in size to the female, we always receive many more females than males, simply for that reason, that smaller fish escape more easily through the meshes of the net or to the eye of the collector than larger ones.

b./ The male example we possess, is much more uniformly colored, less spotted, less ornamented, than the females, which were put into spirits at the same time.8

c/ Kaup’s assertion that the males have marsupial sacs, is not founded on actual observation; he fancied this to be the case, because it is so in the true Lophobranchs.— In Solenostoma it is the female, which carries the ova in a pouch formed by the ventral fins; in the male (Kaup evidently never saw a male) the ventral fins are quite free & do not form a pouch.9

4/ I cannot find any positive evidence of a Lizard uttering a sound during courtship.

5/ In male & female Iguana tuberculata I find the dorsal crest equally developed; slight differences in the length of the lobes are more properly accounted for by the age of the individuals.10

6/ Chamæleo bifurcus from Madagascar. Nothing positive known about the colors. The projections certainly not of a bright colour11

7/ Chamæleo owenii from West Africa. Its colors are known to me from examples in spirit only, & from those they do not appear to be brighter than in other species; they vary much, some specimens being spotted, others uniform. The female has not a trace of a horn. The horns of the male are osseous, in fact excrescences of the facial bones, each horn being covered by a smooth sheath which is part of the general integument. In fact the horns of this species are in structure identical with the horns of those Ruminants which do not shed their horns.12

8/ Nothing is more common than true ocelli in Reptiles & especially in Frogs & Toads; but the ocelli are more frequently black with a white, yellow, red or blue ring, than light-colored with black ring.

9/ In Lizards the females are more frequently the larger sex, than the males; the fact is, I do not at this moment recollect one species, in which the male is the larger.13 You must recollect that lizards propagate before they have ceased growing, & therefore it would be hazardous for a Museum-naturalist to decide from his examples which is the larger sex in each species. In our European lizards the females are the larger; and very large examples of foreign species are generally females.

CD annotations

2.3 Knowing … them?] triple scored pencil; ‘Yes’ pencil


The date is established by the relationship between this letter and the letter to Albert Günther, 27 September [1869].
Labridae is the family of rainbowfishes and wrasses.
Günther refers to plate 86 in Günther 1864–6. CD included Günther’s description of Mollienesia petenensis (now Poecilia petenensis) in Descent 2: 9.
See letter to Albert Günther, 21 September 1869 and n. 7. For more on nesting behaviour in these fishes see Tweddle et al. 1998.
The reference is to Playfair and Günther 1866. See letter to Albert Günther, 21 September 1869 and n. 8.
Günther refers to the family Cyprinodontidae, pupfishes. CD discussed their sexual differences in Descent 2: 7, 9.
CD reported Günther’s information on the coloration of Solenostoma (now Solenostomus) in Decent 2: 22.
The former order Lophobranchii is roughly equivalent to the present suborder Syngnathoidei (pipefishes and seahorses), which includes the genus Solenostomus (ghost pipefish). Günther refers to Johann Jakob Kaup. See letter to Albert Günther, 21 September 1869 and n. 9. In Descent 2: 22, CD cited Günther for the information on the marsupial sac in female Solenostoma.
CD cited Günther’s information on crest size in Iguana tuberculata (now Iguana iguana) in Descent 2: 32.
CD described and illustrated the large bony projections on the upper part of the skull in the male Chamaeleon bifurcus (now Furcifer bifidus) in Descent 2: 34–5.
CD described the three horns of the male Chamaeleon owenii (now Chamaeleo oweni) in Descent 2: 35–6.
CD appears to have misread Günther on this point. In Descent 2: 32, he reported on Günther’s authority that male lizards are generally larger than females.


Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.

Günther, Albert Charles Lewis Gotthilf. 1864–6. An account of the fishes of the states of Central America, based on collections made by Capt. J. M. Dow, F. Godman, Esq., and O. Salvin, Esq. [Read 22 March 1864 and 13 December 1866.] Transactions of the Zoological Society of London 6 (1863–7): 377–494.


Replies to CD’s queries on sexual habits and differences in fish and lizards.

Letter details

Letter no.
Albrecht Carl Ludwig Gotthilf (Albert) Günther
Charles Robert Darwin
Sent from
Source of text
DAR 82: B16–20; DAR 84.2: 168
Physical description
Amem 6pp †

Please cite as

Darwin Correspondence Project, “Letter no. 6911,” accessed on 23 September 2020,

Also published in The Correspondence of Charles Darwin, vol. 17