BY E. J. GODDARD. 859 



cavity, whose contour is thereby rendered very irregular; at the 

 base of each of these projecting masses occurs a large capillary; 

 (2) an irregular layer of longitudinal muscle-fibres, much stunted 

 in size; (3) circular muscle-fibres, constituting a good portion of 

 the wall and representing the chief muscle elements; (4) very 

 irregularly distributed longitudinal muscle-fibres; and (5) an 

 external epithelium, similar in nature to the internal epithelium; 

 immediately beneath this epithelium occur a few large capillaries. 

 This structure, as will be shown later, has no direct relationship 

 to a proboscis, but is, in all probability, connected with the 

 respiratory function. One would at first glance readily imagine 

 that here was shown a rudimentary proboscis which had under- 

 gone degeneration, especially with reference to the radial and 

 longitudinal muscle-fibres; and that the genus in this respect 

 represented a form intermediate between the Rhynchobdellid 

 and Arhynchobdellid types. 



The oesophagus has an elliptical lumen, the long axis being 

 dorsiventral. The epithelium is very little folded in comparison 

 with that of the proboscis-like structure preceding it. In the 

 relaxed condition of the circular muscle-fibres there is present a 

 dorsal median papilla projecting into the lumen, with a groove on 

 either side of it. At the ventral extremity of the oesophageal 

 wall there is a deep wide groove. Its wall consists of (1) an 

 epithelium of columnar cells; and (2) circular muscle-fibres, well 

 developed, and enclosing occasional longitudinal fibres. The 

 chief points of difference between the wall of the oesophagus and 

 that of the proboscis-like prolongation into the pharyngeal lumen 

 are (1) the less folded epithelium in the oesophageal wall; and 

 (2) the practical absence of capillary vessels beneath its 

 epithelium. 



The crop has an epithelium similar to that of the oesophagus, 

 and circular muscle-fibres in its wall. In the relaxed condition 

 it has a dorsal median papilla and an equally well developed 

 ventral median papilla as seen in cross-section, these papillae 

 representing longitudinal folds. Beneath the epithelium occur 

 numerous capillaries, and in this respect the crop agrees more 



