TRACHEATA 413 



the " liver," a very extensive glandular organ which occupies a 

 large part of the cavity of the ahdomen. The secretion which 

 it pours into the intestine is chiefly of use in digesting proteids. 



The cloaca or " stercoral pocket " is an extensive chamber 

 which occupies about one-sixth of the abdominal space ; the 

 faeces seem to accumulate in this, in considerable masses. 

 It opens by the anus, which lies behind the posterior spin- 

 nerets. 



The Malpighian tubules, the excretory organs of the 

 spiders, are four long fine white ducts, closed at their free 

 end and opening at the other into the intestine just where the 

 latter passes into the cloaca. Their secretion contains guanine 

 or some allied body. 



A pair of coxal glands are present in Epeira, but in a very 

 degenerated state ; in Tegenaria they are larger, and show some 

 trace of a duct, and in the young, just-hatched spiders, a duct 

 can be traced which opens to the exterior on the coxal joint of 

 the first pair of legs ; the position of this opening is thus farther 

 forward in the Dipneumones than is usually the case in 

 Arachnids, but in a specimen of another gQnViS,Dysdera rubicunda, 

 a second opening has been described on the third pair of legs, 

 the usual position. 



Two poison glands of a pyriform shape are found just 

 under the integument in the anterior end of the cephalothorax, 

 their ducts traverse the chelicerae and open at the tip of these 

 appendages. In Amaurohius the poison is said to be secreted 

 and stored up through the winter, consequently this genus is 

 especially venomous during the spring. 



The nervous system in Upeira lies chiefly in the posterior 

 half of the cephalothorax ; compared with some other Arachnids 

 it exhibits great concentration (Fig. 236). The supra-oeso- 

 phageal ganglion is large, and supplies nerves to the eyes and to 

 the chelicerae, it is connected by lateral commissures with the 

 sub-oesophageal nervous system. The ventral chain of ganglia, 

 which are distinct in many Arachnids, in the Araneida are fused 

 into one large ganglion situated in the cephalothorax. In 

 Epeira this lies under the sucking-stomach and upon the ends of 

 the gastric caeca, it is star-shaped, with numerous rays, of which 

 the four middle ones on each side are stouter than the anterior 



