376' ORGANS OF DIGESTION. 



as in other classes, to protect it from the hard shells and 

 other dense substances taken in along with the food. This 

 dense epithelium is easily detached after death, and is often 

 found loose in the cavity of the gizzard. The muscles of the 

 gizzard do not form a digastric mass as in gallinaceous birds, 

 but commonly radiate from around a circular tendinous part 

 (122. B. d. D. bi) on each side, as in crocodilian reptiles 

 and rapacious birds, or pass continuously over the sides 

 of the cavity. From the left side of the gizzard a passage, 

 generally short and wide, leads to the third stomach (122. 

 B. e. C. c. D. c.) which in the most common forms of naked 

 cephalopods, as octopus, sepia, and loligo, has a convoluted 

 spiral shape, and presents internally numerous transverse 

 folds of its mucous coat. This third gastric cavity, which 

 has thin membranous parietes and which receives the biliary 

 and pancreatic secretions like the stomachs of other mollusca, 

 is but slightly curved in the sepiola (122. C. c.), it forms an 

 elongated simple stomach in the loligopsis (122. D. c. d.} where 

 the spiral marking is almost confined to the anterior parietes of 

 its pyloric extremity, and in the nautilus (122. B. e.} it forms 

 a globular sac plicated internally, as usual, with parallel 

 folds. It was mistaken by Swammerdam for the pancreas 

 of the cephalopods. The intestine is short and wide in these 

 rapacious animals, and is still destitute of coecum-coli; the 

 alimentary canal is no where imbedded in the substance of 

 the liver as it is in many of the inferior mollusca, and it is 

 not yet distinguishable into small and large intestine, as it is 

 in most vertebrata. Passing to the left side from the third 

 or spiral stomach, the intestine (122. B. /. g. C. d. d. D. /.) 

 generally forms a short single convolution directed down- 

 wards near the left branchial heart, then ascends along 

 the fore part of the liver to terminate between two lon- 

 gitudinal strong muscular bands near the base of the syphon, 

 by a free anal orifice protected by two lateral valvular folds 

 (122. C. e.) The rectal portion of the intestine in the naked 

 cephalopods and the argonaute receives the excretory duct 

 (122. C. k.) of the secreting foUicular ink-gland (122. C. h.) 

 near the anus, and this protecting, excrementitious anal gland 

 appears to be wanting in the nautilus where the enveloping 

 exterior shell sufficiently protects the animal without its aid. 

 The ink-gland, which Monro mistook for the gall-bladder, 



