ETJPAGTJB.TJS. 533 



The nerve chain lies under the bulky flexor muscle* 

 and over a thin layer of integumentary muscles. 



On entering the abdomen the chain slews to the left, 

 passing through the " columellar " muscle to the first 

 ganglion (second abdominal ganglion) in the second 

 segment. This is placed well on the left side of the 

 body, and in a lesser degree so is the third segmental 

 ganglion, which is close to the second, and the fourth. 

 From the fourth to the fifth ganglion there is a longer 

 stretch of connective, which once more brings the chain 

 into the mid-line of the body; and there is another long 

 pair of connectives passing from the fifth through the 

 flexor muscles, till they join the sixth ganglion on the 

 dorsal surfaoe of the muscles under the posterior end of 

 the rectum. From this ganglion branches are given to 

 the uropods, the telson and the alimentary canal. 

 There is a ring round the rectum, but it is uncertain 

 whether there is any actual junction between the two 

 nerves. 



The histology of the nervous system in the higher 

 Crustacea is a rather difficult specialised study, which 

 the ordinary student of Zoology will probably not 

 attempt. More advanced workers should refer to the 

 detailed account of the histology of the shore crab 

 (Carcinus), given by Bethe in the following papers: — 

 Arch. f. mikroscop. anat., v. 44, 1895, p. 579. 

 Ibid v. 50, 1897, p. 460. 



SENSE OKGANS (PI. IV). 



The sense organs consist of a pair of compound 

 stalked eyes, a pair of otocysts, and a number of sensory 

 setae scattered over the body. 



