INTRODUCTION. XXIX 



This apparatus, under a high magnifying power, is seen 

 to consist of several closely packed rows of fine strong 

 short hairs, very commonly arranged together in the form 

 of a heart, the apex of which, directed anteriorly, is 

 truncated. This appears to be the most general appear- 

 ance, though in various genera it is different in form. 

 Its appearance suggests its capability for triturating and 

 grinding food, though it is curious that two such kinds of 

 apparatus should exist at each end of the stomach, the one 

 at the cesophageal entrance, the other near the pyloric 

 outlet. The cavity in which the latter is placed has the 

 walls thickly covered with very short hairs. 



In the genus Talitrus, posteriorly to this apparatus are 

 placed two long ca3ca, one on either side of the posterior 

 opening of the stomach. These caeca are not universally 

 present in other genera. They are delicate prolongations 

 of the walls of the stomach, and gradually narrow towards 

 their free extremity. They probably supply the stomach 

 with a gastric juice. Still more posteriorly, at the point 

 where the stomach terminates and the alimentary canal 

 commences, are situated from four to six long cseca- 

 like lobes, filled with hepatic cells. These are attached 

 to the inferior surface, forming the liver, and are 

 carried] parallel with the alimentary canal. In the 

 Amphipoda, as illustrated in Gammarus, the liver con- 

 sists of four sub-equal lobes ; in the Isopoda, as exempli- 

 fied in Ligia, it is formed of six lobes, two of which are 

 much longer than the other four, and have a slightly 

 waved or tremulous-looking appearance towards the free 

 extremity. From the pyloric orifice of the stomach the 

 alimentary canal in all Crustacea passes, without curve or 

 inflection^ straight to the anal termination under the 

 telson. To this we know of but a single exception, and 

 that on the authority of Professor Alman, who says : 

 " In Chelura, the alimentary canal is so arranged as to 



