1 66 MORPHOLOGY OF INVERTEBRATE TYPES 



ventral dilatatores. The contraction of these muscles widens 

 the lumen of the stomach. Special circular constricting fibres 

 reduce the volume of the stomach and force its contents into 

 the intestine. This section of the alimentary canal represents 

 the midgut and extends backward through the pedicel into the 

 abdomen as a rather wide and slightly curved tube. The in- 

 testine is connected with a so-called ccecal ring in the cephalo- 

 thorax. This ring is formed by two blind processes growing 

 out of the midgut at its juncture place with the pumping stom- 

 ach. Later the two processes unite in front and give off, besides, 

 blind pouches, one pair of which extends forward from the an- 

 terior edge of the ring, a single one backward from the upper 

 wall of the posterior edge of the ring, and four lateral pairs 

 which end blindly in the coxae of the legs. Within the abdomen 

 the intestine forms four pairs of highly branched and anastomos- 

 ing intestinal diverticles which are imbedded in a mass of adipose 

 tissue. For a long time this tissue has been described as " liver," 

 owing to the fact that it binds the diverticles of the intestine 

 firmly together and has the appearance of a large gland. It 

 forms two lobes separated by the heart and extending almost 

 to the mid- ventral line and incloses all the organs. The adipose 

 tissue makes the dissection of spiders very difficult. The hind- 

 gut forms a large stercoral pocket into which the malpighian 

 tubes open. The rectum is short and terminates in an anus on 

 the anal tubercle. Salivary glands are absent. The process of 

 feeding in Agelena is very peculiar and characteristic of true 

 spiders. It is combined with predigestion of the food outside 

 of the alimentary canal. When the fangs have pierced the body 

 wall of the victim, a drop appears between the tips of the spider's 

 maxillary lobes. This drop is supposed to be the secretion of 

 the pedipalpal glands, but an admixture of intestinal juice is 

 probable. It peptonizes all organs and tissues of the victim. 

 The fluid is drawn into the alimentary canal by a combined suck- 

 ing action of the pharynx and pumping stomach. Resorption 

 takes place in all portions of the midgut. 



