80 L. A. BORRADAILE. 



bita is followed by the niid-r/ut or mesenteron — a short, soft-walled tube, which grows gradually 

 narrower from before backwards in consequence of the difference in width between the 

 pyloric division of the stomach and the hind-gut. Through the roof of the mid-gut there 

 opens on each side a short, curved coecum of simple form with its blind end directed 

 forwards. Through the floor open the two bile ducts. 



The Liver (PI. III. fig. F). The same compression of the thorax, which has affected the 

 shape of the stomach, has brought about the displacement of the liver of the hermit-crabs 

 backwards into the abdomen. Starting from the underside of the mid-gut, one close on 

 each side of the middle line, the bile ducts may be traced backwards below the hind- 

 gut, graduall}' diminishing in calibre all the way. On its outer side each duct bears, at 

 almost regular intervals, about a dozen stout tubes or primary ductules, the first of which 

 enters nearly at the level of the last thoracic leg. Each of these ductules curves upwards 

 and inwards over the hind-gut, diminishing in diameter by giving off secondary ductules 

 along its outer side. These in turn give off ductules of a third order, and the latter bear 

 the terminal tubules of the system arranged in tufts. Each tuft opens by a short tube 

 (ductule of the fourth order) on the outer side of the tertiary ductule. The terminal tubules 

 are long and usually cylindrical, though some of them show bead-like swellings at intervals. 

 The whole of the tubules borne on a secondary ductule form, in the natural position of 

 the organs, a well-marked secondary lobule, and all the secondary lobules of a primary 

 ductule form a primary lobule. These lobules, though they are placed at fairly regular 

 intervals along the bile-duct, and roughly correspond on the two sides of the body, are not 

 segrnentally arranged in the abdomen. Moreover, owing partly to the fact that the primary 

 ductules run, not straight upwards round the hind-gut, but also somewhat backwards, the 

 lobules come to overlap one another on the dorsal side of the gut, and their arrangement 

 appears at first less regular than it really is. Besides those arranged on the above system, 

 each bile-duct bears, on its anterior portion, a certain number of tubules directly sessile upon 

 it. These gradually diminish in size from behind forwards, till a short stretch of the bile- 

 duct, just behind the opening, is left quite free from them. Hind wards the bile-duct begins 

 by the junction of two primary ductules. 



We may speak of the whole of the lobules of each side as forming a right and a 

 left liver respectively. The left liver, then, is somewhat smaller than the right, though the 

 difference is not very marked. At the hind end of the abdomen the left liver passes dorsal 

 to the right. The whole of the structures just described are bound together by strands 

 of connective ti.ssue carrying blood vessels. This circumstance, combined with the soft, easily- 

 breakable texture of the liver, makes that organ rather diflicult to unravel. 



C. The Hind-gut. (PI. III. fig. G.) Behind the mid-gut, and stretching from it to 

 the anal opening in a direct course, runs the chitin-lined hind-gut. Its width is even for 

 the first three-fourths or so of its length and then it increases gradually to a greater diameter. 

 There are no rectal coeca. 



Outwardly, the surface of the hind-gut is smooth, but within it is thrown into ridges. 

 These ridges, which are twelve in number, are most marked at the hind end, grow gradually 

 lower forwards, and finally fade away in the middle of the first abdominal segment, some 

 distance from the end of the mid-gut. They are not all of equal size, being alternately large 

 and small, or rather high and low, for there is not much difference in breadth. Each bears 



