ORGANS OF DIGESTION. 359 



compound eyes (B. c. c.) are lodged in orbital cavities above 

 the broad peduncles of the large exterior antennae (B. b.}, and 

 are protected by a spiny prominent median rostrum. The 

 short vertical oesophagus opens into a capacious muscular 

 stomach (A. b. B. d.) in which the teeth are disposed in pairs 

 near the contracted pyloric extremity, and which is surrounded 

 by the numerous lobes of the liver (A. B. n. n. n.). The 

 intestine (A. c. B. e.} receives at its commencement the two 

 hepatic ducts, and passes beneath the heart, (A. e. B. g.) 

 the testes (B. o. o.), and the posterior aorta (A. h. B. .), fol- 

 lowing nearly a straight course to the anus (A. d.) which 

 is situate below the last segment of the trunk. The ab- 

 dominal cavity, containing these viscera is separated from 

 the thoracic containing the branchiae (B. /. /.) by a strong 

 tendinous diaphragm (B. m.). The colic portion (B. /*.) 

 embraced by the bifurcation (A. i.) of the posterior aorta 

 (B. k.) is more wide and dilatable than the rest of the canal, 

 like the colon of insects, and it is provided below with its 

 muscular sphincter, and sometimes with a valvula coli at its 

 commencement. Besides the biliary tubuli which compose 

 the large symmetrical lobes of the liver, and which are some- 

 times reduced to a few pairs of simple follicles in the lower 

 Crustacea, two or three pancreatic tubuli, lengthened and 

 isolated, are occasionally observed to enter the pyloric por- 

 tion of the intestine in the higher decapods, and the soft 

 rudiments of salivary glands are perceived at the sides of the 

 oesophagus in the same animals. The stomach and alimen- 

 tary canal (119. A. b. c. B. d. e.} occupy the dorsal portion of 

 the trunk in the Crustacea, and not the ventral part, as in the 

 vertebrata, which corresponds with the general inverted con- 

 dition of the other organs of the body in the articulated 

 classes. Although the stomach is thus large and powerful in 

 the higher mandibulated predaceous forms of this class, there 

 is often no perceptible gastric enlargement in the short 

 straight intestine of the lower sucking parasitic species. Thus 

 the alimentary canal and the chylopoietic glands are com- 

 paratively limited in their development in all the entomoid, 

 as in the helminthoid forms of articulata, which corresponds 

 with the general carnivorous character of these animals, their 

 inferior position in the scale, and the highly organized con- 



