1 92 DR. W. N. F, WOODLAND ON THE 



distinction is striking. In Aiiguilla the epithelia of the duct and 

 bladder are, as we have seen, quite different in character; in 

 Myrus vulgaris, on the other hand, they are very similar. The 

 duct epithelium consists of a single layer of short columnar cells 

 which is only slightly folded. Yery few capillaries are present in 

 the connective tissue layer underlying the epithelium, though 

 here and there large capillaries are to be seen in transverse 

 section. Thus the duct is not lined by squamous epithelium as 

 in Anguilla. In the bladder of Myrus vulgaris tlie epithelium is, 

 as just stated, similar to that of the duct, the only difference 

 being that the cells are larger. The folding of the epithelium is 

 at most very slight and most pronounced in the region of the 

 opening of the duct ; in the anterior arid posterior regions of 

 the bladder, folding of the epithelium is practically absent. Tliere 

 is never any approach to the degree of folding seen in Anguilla. 

 It is also noticeable that where the epithelium passes over a large 

 capillary (and capillaries are not very numerous) the cells 

 immediately assume a more squamous character. 



Ophichthys (Sph^gebranchus) imberbis Delar. 



In this physostome the plan of construction of the " red 

 body " is essentially the same as that found in Anguilla and Myrus, 

 but there exists in the single specimen at my disposal one 

 modification in connection with the rete miiabile. When 

 the bladder is viewed in situ, a single "red body" is seen to 

 be present which is situated anteriorly in the ventral wall where 

 the duct joins the bladder. A series of transverse sections shows 

 that this "red body'' is, as in the Eel, a large rete mirabile, 

 which, however, is disposed in a different manner in the present 

 instance. The artery and vein run along the right side of the 

 bladder and break up to form the rete in such a manner 

 that the long axis of this lies transversely to the length of 

 the fish (PI. II. fig. 9). The capillaries of the rete mirabile 

 unite as usual to form larger vessels, which here, of course, lie to 

 the left side of the bladder, where they break up anew to supply 

 the epithelium of the gas gland. As in Myriis, there exists no 

 sharp distinction between the glandular epithelium of the duct 

 and that of the bladder, also the capillaries in connection with 

 the epithelia are comparatively few in number. This epithelium 

 consists, as in the two preceding genera, of a single layer of 

 moi'e or less columnar cells which occasionally becomes A'ery 

 slightly folded, but over the greater pai-t of the wall, both of the 

 bladder and the duct, the epithelium is a simple unfolded layer of 

 columnar glandular cells. Strange to say, the cells of the epi- 

 thelium of the bladder in my preparations are distinctly smaller 

 than those ol the duct. Occasionally large capillaries are present 

 in the bladder wall, and where these occur the epithelial cells 

 become, as in Myrus, almost squamous in shape. Small capillaries 

 also exist, though they are not numerous. The epithelium of the 

 duct remote from the bladder becomes much more squamous in 

 character than elsewhere. 



