Vlii. INTRODUCTION. 



beneath the horny cuticle. It is quite possible, however, that 

 these may have sufficed for vision, though, probably, in a very 

 imperfect degree. 



The Legs. 



These are articulated, four on each side, beneath the outer 

 margin of the cephalo-thorax, to an either round, oval, oblong, 

 or heart-shaped, corneous plate, called the Sternum (pi. i., fig. 

 2d) (in this figure the legs are truncated at the first joint. 



The legs oonsist each of seven joints of different lengths (a 

 very few exotic species possessing eight, owing to the sub- 

 division of the tarsus or terminal joint). The following names 

 are given to these joints in the descriptions in this volume (see 

 pi. i., fig. 1, where, on one of the legs, the joints are numbored): — 

 i., the exinguinal ; ii., coxal ; iii., femoral; iv., genual; v., tibial; 

 vi., metatarsal; vii., tarsal. 



The legs vary a good deal in their size and length, both 

 absolutely and relatively ; and the tarsi always terminato with 

 either two or three curvod claws, generally toothed or poctinatod 

 (pi. i,, figs. 8« and 13b) ; usually the pectinations aro confined to 

 the two superior claws, but occasionally the inferior ono also is 

 toothed. The legs are clothed in various ways — with hairs, 

 bristles, and spines (pi. i., figs. 1 and 9) ; in some spiders plumose 

 hairs may be seen. 



In some groups a longitudinal series of small, closely-set, 

 curved, spine-like bristles, may be found on the metatarsi of the 

 fourth pair of logs (fig. 9, a). This is called a Calamistrum, and 

 is used for the purpose of carding or combing out from a special 

 spinning organ (to be described presently) a peculiar flocculus of 

 adhesive silk, which is disposed about the spider's snare, the 

 bettor to entrap its prey. We are indebted to our countryman, 

 the veteran Araneologist, Mr. John Blackwall, for the discovery 

 of this portion of a spider's structure, as well as for our 

 knowledge of its mode of employment and use. Boneath the 

 tarsi (and somotimes the motatarsi) of many spiders is found a 

 more or less compact clothing, ofton quite apad or cushion, of close- 

 set hairs, generally of a papilli form nature (pi. i., figs. 12, 



