Species

198 Species

the origin of these discontinuous forms, but variation is. Bateson stops short of say-
ing that form is a causal factor in evolution, but he does say that symmetry of form
and the repetition of forms (merism is his term for this) are causes of speciation.^43
Indeed, variation from the type (the Specic Differences) is due to a “pathological
accident.”^44 Later, as one of the Mendelian geneticists, Bateson opposed the idea that
there was genetic variation of the kind Darwinian selection required to form species.
In 1913, he wrote:

All constructive theories of evolution have been built upon the understanding that we

know if the relation of varieties to species justies the assumption that the one phe-

nomenon is a phase of the other, and that each species arises ... from another species

either by one, or several, genetic steps. ... [However,] complete fertility of the results

of intercrossing [between members of different “species”] is, and I think must rightly

be regarded, as inconsistent with actual specic difference.^45

Another Mendelian, Hugo de Vries, shortly after proposed a concept of “elemen-
tary species” as pure genetic lines in his 1904 lectures “Species and Varieties”^46 and
in the earlier Die Mutationstheorie.^47 According to the Mendelian view that de Vries
adopted, species in the Linnaean sense actually comprised a number of smaller lines
of pure genetic stock:

Species is a word, which has always had a double meaning. One is the systematic spe-

cies, which is the unit of our system. But these units are by no means indivisible. ...

These minor entities are called varieties in systematic works. ... Some of these variet-

ies are in reality just as good as species, and have been “elevated,” as it is called, by

some writers, to this rank. This conception of the elementary species would be quite

justiable, and would get rid of all difculties, were it not for one practical obstacle.

The number of species in all genera would be doubled and tripled, and as these num-

bers are already cumbersome in many cases, the distinction of the native species of any

given country would lose most of its charm and interest.

In order to meet this difculty we must recognize two sorts of species. The system-

atic species are the practical units of the systematists and orists, and all friends of

wild nature should do their utmost to preserve them as Linnaeus has proposed them.

These units, however, are not really existing entities; they have as little claim to be

regarded as such as genera and families. The real units are the elementary species;

their limits often apparently overlap and can only in rare cases be determined on the

sole ground of eld-observations. Pedigree-culture is the method required and any

form which remains constant and distinct from its allies in the garden is to be consid-

ered as an elementary species.^48

De Vries came to his views through the observation of what we now know to be
alloploid forms in Oenothera lamarckiana, the evening primrose, which de Vries

(^43) Bateson 1894, 19ff.
(^44) As he approvingly quotes Virchow [Bateson 1894, 95].
(^45) Quoted in Forsdyke 2001, 31.
(^46) de Vries 1912.
(^47) de Vries 1901, de Vries 1911.
(^48) de Vries 1912, 11.