( xlv ) 



Fringilla coelebs), for every subspecies {Papilio prlamus poscldon, Papilio 

 priamns priamus, Papilio priamus coelestis). If the classifier wislies to represent 

 the probable phylogeiietic origin of the nnits whicli stand co-ordinated in his 

 system and nomenclature, he has to take recourse to the figurative tree, or must 

 give a kind of pedigree, as we have done in the present work. Fringilla roelrhs 

 does not mean that coelds is a derivation from Fringilla, but that it forms ].art 

 of the genus Fringilla ; and Papilio priamus poseidon must not be interpreted 

 as signifying that poseidon is derived from priamus, but that it is one of the 

 several components which together form the species Papilio priamus. This 

 confusion of ideas has been occasioned by the unfortunate habit, which many 

 classifiers cannot shake off, of regarding the first-described component as the 

 typical form of a species, as the " Sf ammart,"' * as the jdiylogenitically oldest 

 portion of the species, or in the case of a genus as the phylogenetically oldest 

 species of the genus, while it is merc-ly the accidentally first-baptised form. Is 

 the distinction between what is phylogenetically and what is nomenclatoriaUy 

 the oldest really difficult to perceive and to comprehend? 



The classification of the lower categories from individual variety to species 

 is in a different position to that of the higher categories (from genus upwards). 

 While the sijccies and varieties are realities which can be tested by observa- 

 ti(ui of the live specimens and by experiment, there is no such test possible in 

 the case of genera, tribes, families, etc. These higher categories are definable 



groups of allied species. The criterion of their being realities, or, as one is 



used to say, of their being natural, is threefold :— 



(1) The group must be definable— i.e. must not so intergrade with another 



that there is no line of division, or that the line of division is arbitrary. 



(a) The contents of each group must be homogeneous. Elements of 



different origin, though perhaps similar in consequence of convergent development, 



must not be brought together. 



(:5) Each higher category must have a separate definition based on other 



characters than those referred to in the definitions of the respective lower 



categories. The characters which make an animal specifically distinct do not 



make it also generically distinct, nor can the same character upon which a genus 



is based be employed to characterise a tribe or a family. 



To define genera and higher units is not always an easy matter. In order 

 to render a definition precise, a close study is necessary of the forms which 

 come under the unit defined, as well as of the forms of the allied units. Tlie 

 difficulties encountered have induced many authors, especially in Ornithology 

 and Entomology, to propose names for genera, subfamilies, and families without 

 attempting a definition. The naked names thus introduced are a fit testi- 

 monium paupertatis for their authors. In our opinion, the thoroughness of the 

 researches in systematic work can best be estimated from the degree of exactness 



•The weird " .SUmmart " is mm:li cniiiloyud by Gunnan wiiters iii this erroiicoiia and misleading 

 sense. Hec Keichcnow, in Verh. V, liiti-rn. Xuol. Conijresi p. 'J\\ (l'J02). 



