INTRODUCTION. 



12a); this is called a scopula, and is of use in enabling the 

 spider to ascend polished surfaces, as glass, &c. And frequently 

 there is, close beneath the tarsal claws, a compact tuft of hairs, 

 the hairs often of a somewhat club-shape, or squamose nature 

 —to this is given the name of elaw-iuft (pi. i., fig. 13a) ; doubtless 

 it is of use in enabling the spider to traverse uneven surfaces 

 with the greater speed, and is most marked in spiders possessing 

 two terminal claws only, if not entirely confined to them. 

 The Falces. 

 Immediately below tho fore-part of the cephalo-thorax are the 

 Falces (pi. i., figs. 3a, and 5a,a). These are two in number, and 

 each consists of a strong basal joint articulated to the caput, 

 either vertically, or on an inclined plane, or horizontally; 

 moving accordingly, either up and down, or sideways. At the 

 extremity of each is a strong, curved, pointed fang, articulated 

 so as to close down, either in a line along the under side of the 

 falx (pi. ii., fig. 2a), or along its inner side (pi. i., fig 5b,c). Most 

 commonly the fang is met by a longer or shorter row of teeth 

 placed along the inner side of the falx (pi. i., fig. 5d,d), some- 

 times two rows of teeth are present, and occasionally there is 

 an extra strong tooth in front of each falx. The falces are thus 

 rendered most formidable weapons, more especially as each 

 contains, inside, a hollow charged with a poisonous fluid, which 

 is poured into the wound made by the fang, through a minute 

 orifice near its extremity. 



The falces are used not only for seizing and killing the 

 spider's prey, but also for comminuting and compressing it so as 

 to squoeze out the juices into the throat, which is situated 

 immediately behind them. 



By some physiologists the falces are considered to be the 

 homologues of the antennso of insects, abnormally developed and 

 modified for the performance of a special function. The usual 

 truncated form of the fore part of the caput is also considered to 

 have arisen from the disappearance, through " Natural selection, 

 of the fore part of the insect-caput, carrying away with it the two 

 large compound insect-eyes, and leaving only those which now, in 



