Clarifies the notion and use of type-species and applies it to CD's problem with Conchoderma.
The Lodge | Tewkesbury
Feb 15. 1849
My dear Darwin
When I proposed to use Lepas for Balanus, it was owing to my ignorance that Lepas was properly a name of the pedunculate division. In order to have some kind of rule to go by in subdividing genera, it is necessary to trace out the original type-species, on which, like the lineal descendant of an ancient family, the original estates privileges & title must be for ever entailed. That is the theory, but it happens unluckily that a type-species is a modern idea— Linnæus & his immediate successors considered all the the species in a genus as free and equal, and no more thought of making one species the “type” than a Yankee would think of making his eldest son the head of the family.
But as in our modern practice we find that a type-species is a very useful, or
rather an essential, idea in the subdivision of genera, we are obliged by a kind of
fiction to assume that all genera, Linnæus's included, have a
type-species. There are 2 ways of doing this, one by invariably adopting the
first species in the list as the type, the second by determining from
etymological or historical sources, the most appropriate species to bear this honour.
The former plan is based on fact & is unattended with trouble, hence it
has been uniformly followed in Gray's Genera of Birds. The 2
Respecting Lepas aurita; as Olfers in 1814 made it the type of Conchoderma, so it must for ever remain, be the limits, & consequently the definition, of Conchoderma, what they may. Olfers might have made another genus contemporaneously or subsequently of L. vittata, or he might have been unacquainted with such a species,—that is quite immaterial. Oken had no business to give a new name to a genus which included another man's type-species.
Of course you will understand that by type-species I only mean a conventional distinction, referring only to words, not to things; and like human titles, only used as a matter of convenience. Nature knows no more of type-species or “typical groups” than she does of Dukes and Marquesses. Swainson indeed, & other Quinarians talk very mysteriously about “types” as if the latter got their coronets from Nature & not from Man, but all that appears to me to be fudge.
Yours very truly | Hugh E Strickland
- f1 1226.f1See Farber 1976.
- f2 1226.f2G. R. Gray 1844–9.
- f3 1226.f3Living Cirripedia (1851): 67 n. explains CD's retention of Lepas as the generic name.
- f4 1226.f4In Living Cirripedia (1851): 136–52, Conchoderma is used for the genus that includes Lepas aurita of Linnaeus and Branta spp. of Oken.
- f5 1226.f5The quinarian system of classification, proposed by William Sharp Macleay and his followers, arranged organisms into groups and sub-groups, each of which contained five forms whose affinities to one another were such that they could be depicted in the form of a circle. Macleay believed that such a regular scheme existed in the natural world and was evidence of God's plan of creation. See Ospovat 1981, pp. 101–13, and Winsor 1976, pp. 83–7. For CD's comments on William Swainson's views on ‘type’, see Correspondence vol. 3, letter to J. D. Hooker, 31 March ; see also letter from J. D. Hooker, 5 April 1844 and n. 4.