THE SPECIES AND THE VARTE ZZ 
AS BGO LOGTCA L Nine 
BY GOTE TURESSON 
INSTITUTE OF GENETICS, AKARP, SWEDEN 
Bu the last two decades great progress has been made with 
regard to the experimental study of the species problem from 
the genetical point of view. Not only has Mendelism gone far to 
show that species follow the same laws as varieties with regard to 
segregation and combination; it has also been able to demonstrate 
and to a certain extent copy Nature’s own course in the building up 
of new species. This has been admirably shown by Lorsy (1916) 
in the well known case of Antirrhinum rhinanthoides, produced from 
a cross between A. glutinosum and A. majus and so different from its 
parents that a trained botanist would refer it rather to the genus 
Rhinanthus than to Antirrhinum. It is constant in certain characters 
but varies in others in the same way as the Linnean species. The 
extravagant types produced by HERIBERT-Nirsson (1918) from various 
Salix crosses belong to the same category of facts. All of them (Salix 
amerinoides, S. pendulifolia, S. monandra) demonstrate in a striking 
way the process by which new and morphologically. very remarkable 
organisms arise. 
Thus, while the belief that the Linnean species of the present 
genetically represent complicated products of recombined Mendelian 
factors, or genotype compounds, has been strengthened nobody would 
maintain that the problems connected with the formation of the 
Linnean species are exhausted by this demonstration. Most of these 
species are, as every earnest inquirer will find, in their natural 
habitats rather stable products, which do not live in any extensive 
connubium with congeners of other species. The bridgeless gaps 
found between species of the same genus, the final moulding of the 
Linnean species, remain then to be explained. The Darwinian idea 
of selective processes at present offers to most minds a plausible ex- 
planation of the differentiation of Linnean species. Although very 
little is known with regard to the actual play of these selective proces- 
ses, certain facts likely to demonstrate the complex nature of selection 
