Species

200 Species

interfertility and production of fertile offspring, and the constancy of specic char-

acters in different environments. He says,

To sum up: A species is a group of similar individuals differing from other groups in

a number of more or less true-breeding characters, greater than those which often

occur within the limits of a family, and not the direct result of environmental or other

nurtural influences. The members of a species are fertile with one another, but not

readily with other species.^56

Races share some of these features, i.e., they breed true, but they are less marked

than specic characters, and they may be maintained by natural and sexual selection.

However, Darwinian notions of species were the exception rather than the rule for

some time into the new century. Of more signicance was the inuence of Mendelian

genetics, and importantly hybridization.

Lotsy and the Evolution of Species by Hybridization

In a work published in 1916 in English, Dutch botanist Johannes Paulus Lotsy (1867–

1931) proposed both a denition of species and a conception of evolution. He begins

by noting that the concept of species is vague:

All theories of evolution have, until quite recently, been guided by a vague knowledge

of what a species is, and consequently have been vague themselves.^57

Lotsy therefore proposes a denition based on “identity of constitution,” and, cit-

ing Ray, discusses Alexis Jordan’s discovery of variety within all Linnaean species.

He says

Jordan consequently discarded morphological comparison as a criterium for specific

purity and, falling back to Ray (whom he may or may not have known) substituted for

it: nulla certior.... quam distincta propagatio ex semine.^58

From this, he says, Jordan drew the “well founded conclusion”: “The Linnaean
species is no species.” Lotsy therefore proposed a term, the Linneon, for the prod-
uct of Linnaean classication dened as “the total of individuals which resemble
one another more than they do any other individuals” (italics original). The types
contained within a Linneon Jordan called species, and Lotsy calls Jordanons, since
“[b] eeding true to type is ... by itself no reliable test for specific purity.”^59 He then
gives his own, proper, denition of a species:

A species consists of the total of individuals of identical constitution unable to form

more than one kind of gametes.

(^56) Thompson 1934, vol. 2, 1334, italics original.
(^57) Lotsy 1916, 14.
(^58) Lotsy 1916, 21f, italics original. The Jordan here is Claude Thomas Alexis Jordan (1814–1897), a
French botanist who named every variety as a species.
(^59) Lotsy 1916, 23.