INTRODUCTION. 



Araohnids, resembling little scorpions without tails. They are 

 found under logs of wood or stones, as well as among moss and 

 rubbish, and frequently in company with spiders, from which 

 their two, long, crab-like, forcipated claws (or palpi) in front of 

 the legs, will sorve to distinguish them at a glance. 



Of the two remaining, terrestrial, Arachnidous Orders, Solpugidea 

 and Thelyphonidea, we havo no British representatives ; they need 

 not, therefore, bo distinguished here from the spiders. 



So far then as to what is a spider. "We will now proceed to 

 detail, rather more minutoly, the different parts and organs in 

 order to give some idea of what a spider is ; and first of the 



EXTERNAL STRUCTURE. 

 The Oephalo-thorax. 



This consists of the head (caput) and thorax, united (pi. i., 

 fig- 4) ; its integument is always, more or less, hard and corneous, 

 and is marked with two obliquo indentations towards its fore part, 

 indicating a large, somewhat wedge-shaped portion, at the 

 anterior extremity (pi. i., figs. 3b and 4b) ; this wedge-shaped 

 portion is the caput ; the distinctness, with which it is marked 

 off from the rest (or thorax), is exceedingly variable, and its 

 fore extremity is always, more or less broadly truncated, or 

 rounded off. The thorax is marked with three or four grooves 

 or indentations on each side (pi. i., figs. 4c,d,ej; and 3c,d,e l f), 

 varying in depth and completeness, but almost always traceable, 

 and converging from near the margin to a point near the centre, 

 where there is either a small linear furrow, a simple dilated 

 depression, or sometimes a deep, curved, transverse indentation ; 

 this is called the thoracic indentation (pi. i., fig. 4g) ; the transverse, 

 converging, lateral indentations indicate the four thoracic seg- 

 ments on each side. These segments and the caput are now 

 soldered together ; but, without a doubt, at one period of the 

 spider's genealogioal history all of them were separate from each 

 other, and each was articulated to tho thorax proper, the posi- 

 tion of which is marked by the present thoracic indentation. 



Besidos these indentations, the cephalo-thorax is often marked 



