Holt and Calderwood — Report on the Rarer Fishes. 47"?' 



large and conspicuous mesentery. On the left side a long lobe of liver extends 

 almost the entire length of the cavity bending into a median position for the 

 second half of its course. On the right side the liver forms only a small leaf-like 

 process j^rojecting from the basal portion, but on this side of the median mesen- 

 tery a fold of the intestine passes backwards. The stomach shows a well-defined 

 fundus, the duodenum springing from the middle of the inferior surface. The 

 pyloric coeca are very numerous ; a delicate air-bladder is present. It is almond- 

 shaped, and is covered on its under-surface by black peritoneum. On opening 

 the bladder a circular aperture bounded by a sphincter muscle is at once visible in 

 the centre of the median dorsal surface. This aperture has no duct in connection 

 with it, but is merely a perforation of the upper surface. At the same time it is 

 noticeable that the bladder is very loosely held in its position by membranes from 

 the dorsal wall, which form a secondary cavity above and to each side of the bladder. 

 This inclosed part of the body cavity, therefore, communicates freely with the 

 air-bladder, and is probably utilized when the gases of the bladder increase in 

 volume. At the anterior end, there are two rete mirabile of considerable size 

 which may provide for such an increase ; and the space found in the abdominal 

 cavity proper, owing to the viscera not entirely filling the cavity, as already men- 

 tioned, seems also to indicate that a great increase does take place. Some such 

 provision might be necessary if the creature has the habit of frequenting water 

 of widely different pressures during short intervals of time, or has a much greater 

 vertical range than the records of its capture have yet shown. 



The kidneys show an arrangement not unlike that seen in Cyclopterus. There 

 is a single-body kidney which divides anteriorly (at a level, in this case, of the 

 eleventh vetebra) into two branches, which pass forwards and outwards to the 

 region of the ex-occipitals and there forming thickened masses, may probably 

 represent persistent head-kidneys.* Unlike Cyclopterus the single-body kidney 

 is extended backwards also. It passes down the haemal arches of the tail to the 

 level of the thirty-eighth vertebra. The entire organ may be said to stretch half 

 the length of the body and tail of the fish. 



In the skull, the muciferous cavities extend widely over the surface, imme- 

 diately beneath the skin. Behind the eye, the opercular muscles occupy their 

 normal position, but the skull on all other parts of its surface is soft to the touch 

 through the presence of the cavities. The conical snout seems to form the central 

 point from which the various channels diverge. The two cavities which occupy 

 the interorbital space pass backwards from the region of the frontals to the level 

 of the posterior margin of the operculum. Above the maxillae, also, cavities 

 extend which send slender branches upwards behind the eyes, so as almost to 

 join the cavities of the frontal region, and thus encircle the orbits. 



* As in Cyclopterus and Anguilla, this head kidney appears to be degenerate and f unctionless in the adult. 



