XXXVI. INTRODUCTION. 



The first subdivision of the Araneidea, necessary to he noted 

 here, is into Families. By some authors a previous subdivision is 

 made into Suborders; but, -whatever scientific truth there may be in 

 Suborders generally, the whole group of spiders is too homogeneous, 

 practically, to need it, or, perhaps, indeed to admit, scientifically 

 speaking, of such a primary subdivision. Mr. Blackwall divided 

 the Araneidea into three Tribes. One ( OctonoculinaJ characterized 

 by possessing eight eyes ; another fSenoculinaJ having six eyes ; 

 the third (Binoculina) with two eyes. But, although this sub- 

 division may seem to possess a certain amount of practical 

 convenience, it sets at defiance almost all the other categories 

 of generic characters ; bringing together spiders widely different 

 in every other respect excepting in the mere number of 

 the eyes ; and- separating as widely other spiders of close 

 and undoubted affinity to each other, differing only in that 

 number. Equally untenable, as a basis of scientific classification, 

 although of very great interest, are the different kinds of snares, 

 upon which Latreille (followed since by others) based his 

 subordinal groups, some of which, Orbitelaria and Retitelaria, 

 have already been noticed. 



Passing over, then, such primary groups as those above men- 

 tioned, Families are characterized according to various modifica- 

 tions of general form, as well as by some few common, but 

 peculiar, structural details, occasionally supplemented by habits 

 and modes of life. Next to Families come the Genera. These 

 are groups, characterized by the ultimate details of the structure 

 of various parts, including the form and relative dimensions of 

 the Cephalo-thorax and Abdomen, Legs, Maxillae, and Labium ; 

 sometimes also of the Falces ; more rarely the armature of the 

 legs ; and, always, the number, relative size, and position of the 

 eyes. 



There is hardly any need to remark that, although it is usually 

 implied (and most commonly it is the fact) that a Family is a group 

 of Genera ; just as a Genus is a group of Species ; yet a Family, 

 a Genus, aad a Species may be (and have often been, among 



