Species

130 Species

conclude, that the tribes thus distinguished have not descended from the same original

stock. This is the purport of the word species, as it has long been understood by writers

on different departments of natural history.

Later, in his 1843 The natural history of man, he writes:

Species, then, are simply tribes of plants or of animals which are certainly known, or

may be inferred on satisfactory grounds, to have descended from the same stocks, or

from parentages precisely similar, and in no way distinguished from each other. The

meaning of the term species ought always, for the reasons now explained, to have

been restricted to this precise import; and when the expression is used in the following

pages, it is so to be understood.^64

Prichard’s view may have influenced the well-known view of William Whewell
in 1837 that “species have a real existence in nature, and a transition from one to
the other does not exist.”^65 The transition envisaged here is most probably one of
plenitude than transmutation, but by 1837 Geoffroy’s views on evolution were widely
known, as was Cuvier’s demolition job on Lamarck in the Éloge.

Louis Agassiz: The Last Fixist and the Lonely Platonist

Louis Agassiz, Cuvier’s devotee and intellectual successor, concurred with Cuvier

and Prichard on the constancy of species. Notwithstanding this, Agassiz did not

expect that there would be a set of characters unique to all members of a species;

resemblance was not itself clear or absolute. In an early short note, he denied that

characters gave the species, and instead insisted that while there was a process

that underlay the forms of species, there need not be any diagnosable characters

that all members of the species exhibited, bringing to mind the Lockean distinc-

tion between real and nominal essences. Like Locke, Agassiz was rejecting the

nominal and accepting the real essence, and it was a generative notion of real

essence at that:

... no so-termed character—that is, no observable mark—can be so striking as to indi-

cate an absolute specific distinction; but at the same time, it should never be regarded

as so trifling as to point to absolute identity; that characters do not mark off species,

but that the combined relations to the external world in all circumstances of life do.^66

Agassiz’s version of the real essence here is the set of causal relations of the organ-

ism throughout its lifecycle to its environment, and he cites the sometime inclusion of

the male and female of a species in separate taxa. Agassiz explicitly rejected a diag-

nostic notion of species, and in effect anticipated the later notion of “cryptic species”

of Mayr. However, in practice, he was not so exact. He distinguished between eight

(^64) P r icha rd 1843, 10.
(^65) W hewell 1837, 626, Vol. 3; quoted in Hull 1973, 68.
(^66) Agassiz 1842, italics original.