172 (iÖTK TLUKSSON 



When it is found that the Linnean species is made up of a great 

 number of hereditary forms, and when it is further estahhshed 

 (TuRESSON, 1922 a and b) that such hereditary forms are found in 

 nature to be grouped into different types, or rather complex-types, 

 confined to definite habitats, the necessity of an intensive study of the 

 Linnean species and their habitat types, or »races», becomes pressing. 

 It is evident that this study of the species and their hereditary habitat 

 types as rehited to environment represents another phase of ecology 

 than those previously studied. Its methods of attacking the problems 

 must also be different. Our study necessitates the cultivation on a large 

 scale under the same conditions of a great number of individuals of the 

 species, collected in different habitats in nature, supplemented by 

 breeding experiments. It seems appropriate for several reasons to 

 denote this study of species-ecology by the term genecology (from the 

 Greek »genos», race, and »ecology») as distinct from the ecology of the 

 individual organism, for which study the old term autecology seems to 

 be the adequate expression. 



From the point of view of genecology the Linnean species repre- 

 sent a genetically complex community, the distribution and the com- 

 position of which is largely determined by the ecological factors and 

 the genotypical constitution of the individuals composing the species- 

 community. The Linnean species represents as such a much important 

 ecological unit, to which unit the name ecospecies has been given by 

 the present writer. The hereditary variation within the ecospecies and 

 the relation of this variation to habitat conditions furnishes one of the 

 most important problems in genecology. In the genecological work 

 performed by the writer it has been shown that the ecospecies becomes 

 differentiated into different hereditary types when distributed over an 

 area presenting different habitats. This has been found to be true not 

 only of ecospecies distributed over areas climatically different in North 

 and South, or in East and West, but also of ecospecies confined within 

 a limited geographical range, where topographical differences (for in- 

 stance cliffs and sand dunes) alternate. In such areas there has also 

 been found an alternation of the hereditary habitat types (cliff type 

 and sand dune type) of the ecospecies. The term ecotype has been 

 proposed by the writer to cover the ecological sub-unit of the ecospecies 

 arising as a result of the differentiation of the species-population in 

 response to particular habitat conditions. It is clear that common and 

 widely distributed species furnish better objects for genecological stu- 

 dies than rare ones, where geographical isolation may complicate the 



