CRUSTACEANS. 603 



then curves into the stomach, which is placed almost perpendicu- 

 larly. The stomach is compressed laterally, has thick muscular 

 walls, and is armed internally with many oblong rows of horny 

 spines. The pylorus projects conically into the intestine, which 

 then proceeds horizontally backwards, lying in the first part of its 

 course close upon the oesophagus that runs in the opposite direction, 

 and lies below it 1 . In Squitta the stomach is small, muscular, 

 triangular, armed in its posterior or pyloric portion with horny, 

 pointed spines. In the ten-footed crustaceans the oesophagus mounts 

 almost directly upwards. The stomach is capacious, and in its first 

 part entirely membranous. The uppermost and hindmost or pyloric 

 portion of the stomach is supported by hard parts, and therefore, 

 even in the empty state, remains expanded. To these hard parts 

 teeth are attached internally, by the assistance of which the food is 

 comminuted. The epithelium of the stomach, moreover, is covered 

 with numerous prolongations or colourless hairs, invisible to the 

 naked eye, whose points are directed backwards 2 . To this stomach 

 different muscles are attached, which arise on the inside of the 

 cephalothorax, and which can also work upon the teeth described 

 above. These muscles are, beyond doubt, subject to the will of 

 the animal, and consequently we have here the rare example of an 

 organ of vegetative life that is moved by muscles of animal life. 

 fn some ten-footed crustaceans one or more blind appendages to 

 the intestinal canal are observed, which probably are secreting 

 organs 3 . There are some species in which two such blind tubes 

 terminate in the intestine close to the inferior opening of the stomach, 

 whilst a single third tube is attached to the intestine lower down. 

 It is, however, this last unpaired tube which alone occurs in most. 

 Unless this tube be regarded as an organ for the secretion of 

 urine, no parts are known which correspond to the vasa urinaria of 



1 Recherches sur I' Hist. not. et I'Anat. des Limules, p. 17, PL II. fig. i c, figs. 



2 At the hindmost part of the stomach, behind and under the above-mentioned 

 teeth, these hairs may be distinguished even with the naked eye. The stomach of the 

 cray-fish has been often described and figured. We content ourselves with referring to 

 the latest investigations alone, those of F. OESTERLEN, in MUELLER'S Archiv, 1840, 

 s. 387441, Taf. xii. 



3 See DUVERNOY in the second edition of CUVIER Le$. d'Anat. comp. v. pp. 228, 

 229. In as far as they open close to the pylorus these blind appendages may perhaps 

 be compared with the pancreas ; but ordinarily they are inserted further backwards. 



