INTRODUCTION. XXXVU- 



exotic spiders) based upon a single individual ; for, after all, the 

 "individual," whethor it be a spider or any other living creature, 

 is the sole reality in nature ; and nocessarily possesses in itself 

 all the characters upon which classification is based, be they 

 Family, Generic, or Specific. The names, therefore, given to the 

 various groups or divisions recognized in classification, are 

 merely convenient abstractions denoting the different relations of 

 individuals, or groups of individuals, to each other. 



The specific characters, or those by -which Species are 

 characterized, now only remain to be noted. They are 

 those of size and colour, and the pattern formed by its 

 distribution ; also slight differences in the rolative sizes and 

 position of the eyes ; the height and form of the clypeus ; 

 as well as the relative length of the legs, and their 

 special armature. In some groups of spiders the comparative 

 length, breadth, and depth of the cephalo -thorax is a valuable 

 specific character ; so are also its normal indentations, as well 

 as the strioe and punctures when present. In all adult 

 male spidors the palpi (especially the projections or apophyses, 

 when present, on the different joints) and the palpal organs, 

 by their varying structure, afford the most trustworthy of all 

 characters for distinguishing species, even when in other 

 respocts the differences may be exceedingly slight ; and in almost 

 all female spiders (when adult) the form and structure of the 

 genital aperture give us some of the best characters for distin- 

 guishing the species, in that sex, of nearly alliod spiders. 



Species, then, are groups of individuals, in each of which the 

 above characters called specific come together. Occasionally, how- 

 ever, individuals are found in which all the specific characters 

 meet, excepting one or two of the least value, such as size and 

 colour, and occasionally pattern. These constitute varieties. 



The subject of classification, being practically exemplified in 

 each of the ensuing descriptions of spiders, need not be further 

 gone into here. 



