TRACHEATA 413 
the “liver,” a very extensive glandular organ which occupies a 
large part of the cavity of the abdomen. 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 hes 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 Lpeira, 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 genus, 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 Amaurobius 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 “petra 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 
