CHAPTER III 



THE CATEGORIES OF VARIANT INDIVIDUALS 



Biological inquiries in general involve recognising that 

 individual animals may be grouped in various ways, and 

 in investigations of variation, heredity and evolution the 

 characteristics of such groups are the subject of inquiry and 

 the measure of divergence. Investigation of the nature and 

 status of these groups and their relationship one with another 

 is an indispensable preliminary to the study upon which we 

 are engaged. 



The levels of evolutionary divergence most usually indi- 

 cated by the species and variety have been subjected since 

 Darwin's time to a careful scrutiny from divers points of view 

 and numerous categories have been proposed to designate 

 groupings of individuals other than the traditional species 

 and variety of taxonomy. Historically we may date the 

 commencement of serious analysis to Alexis Jordan's publi- 

 cation of his work on elementary species, and to such pioneer 

 work as Waagen and Neumayr's studies of ' Formenreihe.' 

 The conception of geographical races may be dated to earlier 

 workers (Kant, Pallas, Gloger [cf. Rensch, 1929) ). 



An admirable study of the lowest systematic categories 

 has been published by du Rietz (1930), who discusses criti- 

 cally the status of the various groups proposed and the syno- 

 nymy of the terms used, du Rietz's list is defective in one 

 or two important respects. He discusses neither palaeonto- 

 logical categories nor physiological differentiation, nor does 

 his survey, which is mainly based on botanical data, include 

 such divisions as colonies, etc. 



The most commonly recognised categories are, of course, 

 those used in taxonomy. In addition there are a number of 

 others in regular use in various branches of zoology, which 

 either have not been absorbed into the hierarchy of systematic 



