356 ORGANS OF DIGESTION. 



into the canal, as in many insects. The strong short mandi- 

 bles and the large palpi of the scorpions terminate in prehen- 

 sile organs, like the pincers of a crab, and embrace a capa- 

 cious buccal cavity like the stomach of a crustaceous animal. 

 From this wide oral sac, which is surrounded above by the 

 ganglionic cerebral ring, the alimentary canal passes, narrow, 

 tubular, and equal, through the abdomen and the tail, to the 

 beginning of the last caudal segment, where it opens on the 

 lower surface. In its course from the narrow oesophageal 

 part, which passes through the nervous collar to its anal 

 termination, the intestine of the scorpions forms neither crop, 

 gizzard, nor gastric enlargement ; but the portion contained in 

 the abdomen, like a tubular stomach, is surrounded with the 

 numerous lobes of the liver, which communicates with its 

 interior by five pairs of short wide ducts, opening at regular 

 distances along its sides. These five pairs of hepatic lobules 

 are more isolated conditions of the ramified intestinal cceca of 

 the halithea and other annelides, and at the lower part of 

 this elongated stomach originate also four distinct ramified 

 vessels, like some of the branched biliary vessels of insects, 

 but which here communicate with the two anterior compart- 

 ments of the heart, and with other parts of the vascular sys- 

 tem, as if they conveyed nutriment to the blood. Thus, 

 while the masticating organs of the arachnida approach these 

 carniverous animals more nearly to insects, their straight and 

 narrow alimentary canal, and the compact lobulated condition 

 of their liver, connect them with the Crustacea. 



XIII. Crustacea. Like the spiders and scorpions of the 

 land, the crustaceous inhabitants of the waters are cunning, 

 cruel and carnivorous animals : with means of rapid locomo- 

 tion and numerous acute organs of sense, and with a solid 

 exterior protection and strong organs of prehension and 

 mastication, they are well fitted for preying on all kinds of 

 animals in the rich element they inhabit. They subsist on 

 living or dead animal food both higher and lower than them- 

 selves in organization ; most of them are in constant warfare 

 with each other, and many, from being free, become fixed and 

 parasitic in their adult state. The mouth in the higher 

 Crustacea is generally furnished with a pair of strong palpi- 

 gerous mandibles, and five or more pairs of jointed extended 

 maxillae, which move transversely, and support likewise articu- 



