PHYSIOLOGY OF THE INVERTEBRATA. 



49 



some species there existed three pharyngeal apertures, 

 through which the juices expressed from the captured insect 

 by the action of the maxillary plates were filtered, as it 

 were, into the narrow oesophagus. In Mygale, however, 

 there is only one aper- 

 ture." The oesophagus 

 leads into a stomach pro- 

 duced into several lateral 

 appendages, which some- 

 times extend into the 

 limbs. The stomach of 

 Tegenaria domestica, and 

 other species, is capable 

 of great distension, and 

 passes directly into the 

 intestine, which dilates 

 into a rectum and then 

 jberminates in an anus. 

 Into the intestine open 

 several so-called biliary 

 ducts, The latter are 

 thrown off from a large 

 organ (Fig. lo) situated 

 on either side of the in- 

 testine, but which is 

 greatly concealed by large 

 masses of adipose tissue 

 occupying the sides of 

 the abdomen. This organ 

 has not the function of a 

 liver, for its secretion is 

 of a pancreatic nature. 



In front of the rectum open two long slender tubes which 

 often branch ; these are the Malpighian tubules. Salivary 

 glands are also present. Spiders are carnivorous animals, 

 and the females are sometimes addicted to cannibalism. 



D 



Fig. io. — Diagram of the Alimentary 

 Canal of Pholcus rivulatus. 



a = salivary glands. b = stomach. 



c = intestine. (^ = so-called liver. 



e = Malpighian tubules. /= rectum. 



