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masticating organs, whilst their straight narrow alimentary canal 

 and the compact state of their liver, ally them to the Crustacea. 



Like most other carnivorous articulata, the cunning, cruel, 

 aqautic crustaceans are provided with prehensile and masticating 

 organs well suited to destroy the prey in the rich element they in- 

 habit. The maxillae vary from one to five pairs, but are wanting 

 in the lower orders. The alimentary canal is generally without 

 convolutions, and opens by two apertures. The decapods present 

 a narrow oesophagus, leading to a capacious muscular stomach, 

 furnished with numerous solid calcarious teeth, and a straight in- 

 testine occupying the dorsal portion of the trunk, and receiving- 

 near its commencement the biliary and pancreatic ducts. The 

 salivary glands are absent except in the higher orders, where rudi- 

 ments of them are perceived surrounding the oesophagus. The 

 mucous membrane forms rugae in the oesophagus and stomach, 

 but not in the intestine, and the peritoneum ibrms no mesentery. 



Cyclo-gangliata, Grant — Mblluscq, Cuvier. — This great divi- 

 sion of the animal kingdom being destined chiefly to subsist on 

 soft food, masticating organs are little required by them, hence they 

 are often but sliohtly developed, and in some cases wholly absent. 

 But their food is greatly varied and often coarse, so as to require a 

 complicated form of alimentary canal, and a high development of 

 glandular apparatus. The digestive organs of the tunica t a closely 

 resemble those of the conchifcra, being a little more complicated in 

 the latter. Both are destitute of prehensile or masticating organs, 

 and depend for their supply of food on the respiratory currents. 

 They possess a short wide oesophagus, opening into a capacious 

 muscular stomach, without teeth, and receiving the biliary ducts. 

 The intestine is generally short, wide, and convoluted. The con- 

 chifera differ from the tunicata by their long and convoluted intes- 

 tine passing between the two aorta?, through the fleshy substance 

 of the ventricle, and the mass of the liver. The terrestrial pulmo- 

 nated gasieropnds present a more complicated digestive apparatus 

 than the acephalous mollusca, especially those which feed on vege- 

 table substances. They are provided with a pair of horny jaws, a 

 muscular tongue and proboscis armed with sharp recurved spines, a 

 large pharynx, a long oesophagus, and a capacious stomach, divided 

 in the phytophagous species, into several compartments, fur- 

 nished internally with teeth, and receiving the biliary and pancre- 

 atic secretions. One or two pairs of salivary glands lie around the 

 oesophagus, and the liver is of considerable size. The intestine 

 is long and convoluted, and opens in common with the genital or- 

 gans on the right side, near the anterior extremity of the body. In 

 the pteropods and cephahpods, the oesophagus passes through the 

 cranial cartilage and ganglionic ring, sometimes dilating into a 

 crop before entering the muscular gizzard, which is often lined 

 with a thick coriaceous epithelium. The intestine is short and 

 wide in the carnivorous species, destitute of coecum-coli, not dis- 

 tinguished into large and small as in the vertebrata, and no where 



