THE CATEGORIES OF VARIANT INDIVIDUALS 67 



by their members occupying a more or less clearly delimited 

 geographical area. Among the students of invertebrate 

 groups no such regularity of usage obtains and there is evi- 

 dently no general tendency, easily detected, for the subordinate 

 groups to be spatially segregated. We discuss at some length in 

 Chapter IV the question whether there are any real grounds 

 for this difference in procedure and its implication. For the 

 moment we are concerned only with the categories themselves. 

 How different the procedure among students of invertebrate 

 groups may be will be seen from the following extracts. 



Pilsbry (1919, p. 277), in treating of the subordinate divi- 

 sions of species of African land snails, distinguishes between 

 ' those of racial value or subspecies in the sense of forms charac- 

 teristic of geographic areas or habitats,' and ' the different 

 forms (mutations of de Vries (?) ) occurring together in the 

 same colonies and doubtless interbreeding.' These he calls 

 mutations. This usage of ' subspecies ' is found largely among 

 lepidopterists (but cf. Wheeler, 191 3 (ants) ). 



Bequaert (19 19, p. n), who evidently feels that it is not 

 possible to recognise geographic units of the same status as 

 those in other groups, uses the term variety for his subordinate 

 divisions in a ' neutral ' sense, i.e. without any presumption 

 as to their true status as geographical races or individual aberrations 

 or elementary species. His varieties oiEumenes maxillosus (African 

 wasp ; p. 59) seem to occupy separate parts of the range of 

 the species (p. 60), but they are not to be considered geo- 

 graphical races, as they ' do not inhabit a given country to 

 the exclusion of all others.' Here we see geographical units 

 less distinctly segregated than in other cases, but still perhaps 

 deserving that status. 



The term variety is generally used in dealing with inverte- 

 brates in the ' neutral ' sense of Bequaert for anything from 

 a single rather distinctive individual in a limited number of 

 specimens representing a species to the kind of group seen in 

 Eumenes maxillosus. It is given regularly to clearly marked 

 and distinctive groups numerically well represented, the 

 individuals of which occur as a certain percentage in any part 

 of the range of a species, but are not restricted to a particular 

 locality (colour-classes of land snails). There seems to be a 

 fairly well-established practice of distinguishing between sub- 

 species and varieties in the sense outlined above according 



