AGELENA N^VIA WALCKEN^R 165 



of extensors, their function being performed by the elastic inter- 

 articular membranes. 



Glands. The most important glands are the poison 

 glands and the spinning glands. The poison glands are situated 

 in the head and occupy a large portion of its cavity. There are 

 two of them, one for each chelicer. The glands are sausage- 

 shaped, with a spiral muscle in their wall. The duct runs be- 

 tween the flexor and extensor of the fang and terminates in a 

 small opening under the tip of the latter. The action seems to 

 be voluntary, the spider using the poison only in self-defence. 

 The numerous spinning glands are situated in the abdomen. 

 A separate duct leads from each gland to a spinning tube on the 

 spinnerets. The silk is a secretion which hardens from contact 

 with the air. Two coxal glands of uncertain function are sit- 

 uated in the cephalothorax. Their ducts open between the first 

 and second pair of legs. It is probable that all arachnids pos- 

 sessed once a pair of openings at the base of all four pairs of legs. 

 The coxal glands are modified nephridia with a blind end. A 

 group of pedipalpal glands is contained in the maxillary lobe of 

 the pedipalpi. Each gland has a separate opening. The secre- 

 tion has a peptonizing ferment and is used in predigestion. 



Digestive system. The digestive system of Agelena, as 

 that of all spiders, is peculiar in many respects. The mouth opens 

 ventrally so that the upper lip sits really in front of it and the 

 lower lip behind it. The maxillary plates of the pedipalpi are 

 at the sides of the lower lip and not in front of it as is the case 

 with the maxillae in insects. The foregut is clearly divided into 

 a pharynx, oesophagus and pumping stomach. The pharynx 

 has two chitinous plates in its intima provided with special 

 muscles. It leads directly upward and its posterior end is con- 

 siderably thicker than the oesophagus. The latter is a cylindrical 

 curved tube lined with chitin. It opens into the pumping 

 stomach, the wall of which has three chitinous plates and works 

 as a pump. The upper chitinous plate serves for the attachment 

 of the dorsal dilatator, the ventrolateral plates for that of the 



