Annelides. 89 



ciiticular investment terminates suddenly at the part corresponding 

 to the cardiac orifice of the stomach. It is exceedingly muscular, 

 and its parietes are nearly half a line in thickness ; the fibres run 

 principally in a longitudinal direction, by which means the interior is 

 thrown into a number of longitudinal rugae, circular fibres are how- 

 ever very conspicuous in some parts : some of the longitudinal fibres 

 appear to be inserted into about half the base of the cartilaginous 

 jaws. The separate fibres, when examined with a power of 400 li- 

 near, are found to exceed greatly in size those of the muscular tunic, 

 and, like them, they are remarkable for their dotted appearance, (fig. 

 eand/, p. 92). The stomach is nearly cylindrical in shape; its 

 parietes are thin and easily lacerated, it is slightly constricted at inter- 

 vals of about a quarter of an inch, at which points it appears to be 

 firmly connected by membranous septa to the walls of the abdominal 

 cavity; it expands a little at its lower third, just before it joins the 

 large intestine or rectum, which appears, as far as size is concerned 

 externally, to be nothing more than a continuation of the stomach. 



The coeca are given off from the lower portion of the stomach, one 

 on each side ; they are little more than half an inch in length, and 

 about a line in diameter : in some specimens these cceca are larger 

 at their blind extremities than in the middle, in others they gradually 

 diminish in size from their point of connexion to their free extremi- 

 ties : in their natural position they are firmly bound down by cellular 

 tissue to the sides of the rectum. Unless the animal be dissected in 

 water, these cceca may easily be overlooked. The rectum is of a co- 

 nical figure, being broad above, where it is connected with the sto- 

 mach, and small below, where it forms the anal outlet, which opens 

 externally on the dorsal surface of the animal immediately above the 

 sucking disk. It varies from three quarters to an inch in length, and 

 is about a quarter of an inch in diameter at its broadest part. 



The interior of the oesophagus, as has been stated, is of a white co- 

 lour, and is thrown into longitudinal rugae ; it is lined with a cuticle 

 of a white colour, which ceases abruptly at the cardiac orifice of the 

 stomach, where there is a constriction ; fi-om the muscular fibres being 

 arranged principally in a longitudinal direction, it is capable of con- 

 siderable dilatation, in which it differs much from the same part in the 

 medicinal leech. The interior of the stomach is of a red colour, and 

 consists of wavy folds of mucous membrane ; it appears to be quite 

 free from villi, but the intestine with which it is continuous is largely 

 supplied with them : there is a tolerably well developed constriction 

 or pyloric valve at the junction of the stomach and intestine. The 



