LIGIA. 81 



formed by a single cell, the nucleus of which can be seen 

 near the centre of the gland (n.c.d.). 



The hepatopancreas. This is also known as the liver, 

 and the digestive gland; the last name describes its true 

 function. In Ligia it consists of three pairs of tubules, 

 which extend from the pyloric region of the stomach to 

 the posterior end of the abdomen, where they gradually 

 taper off, and are generally doubled back for a short 

 distance. The three pairs are situated in relation to the 

 intestine, dorso-lateral, ventro-lateral and ventral (PL II., 

 fig. 16, v. hep.,vl. hep.). The muscles of the walls of the 

 distal two-thirds of the tubules are so arranged, that a 

 spiral appearance is produced. The spiral arrangement 

 of the muscles no doubt aids their peristaltic con- 

 tractions. The tubules of each side open into the 

 pyloric region of the stomach by a single aperture, 

 behind and below the ventro-lateral teeth. The two 

 ventrally placed tubules of each side fuse and then open 

 into the stomach. Anterior to the opening the 

 dorso-lateral tubules curve ventralwards, and fuse with 

 the anterior end of the ventro-lateral tubules. A small 

 tube is given off from the front of the common hepatopan- 

 creatic duct, which runs forward for a short distance and 

 ends blindly. The epithelial cells of the hepatopancreas 

 are of two kinds — large secreting cells containing large 

 nuclei, and smaller cells which may be either young 

 secreting cells, or cells of an excretory nature. 



The physiology of the digestive system of terrestrial 

 Isopods has been studied by Murlin (1902). He finds 

 that the secretion of the hepatopancreas, which may be 

 liberated by the dissolution of the cell, fragmentation of 

 the cell, or evacuation from the cell, contains ferments, 

 which are able to act upon proteids, carbohydrates and 

 fats. 



