336 PROFESSOR FRANK J. COLE 



asymmetrical openings — the apertures of the segmental ducts (s.d.) The left seems to 

 be the larger, and is certainly anterior to the right. There thus appears to be in 

 Myxine, in this dorsal cloacal chamber, a representative of the distinct and undoubted 

 urogenital sinus of the lamprey, but Burne argues with much reason " that the uro- 

 genital sinus of the lampreys is absent in the Myxinoids, and that in the latter the anus, 

 ' porus genitalis,' and ureters open into an integumentary cloacal chamber, similar to the 

 cloacal chamber common to anus and uro-genital sinus in the lamprey " (12, pp. 494-5). 



According to Burne, the porus genitalis is surrounded by a large diffuse gland, the 

 histology of which is said to make it highly probable, in spite of its deep position, that 

 it represents modified lateral slime glands. As v/ill be seen on reference to fig. 5, 

 the slime glands {s.s.) are apparently absent from the two myotomes (89, 90) of the 

 cloacal region, and when it is remembered that the supposed genital pore gland 

 completes the only break in this linear series, and that the true slime glands immediately 

 posterior to it are also largely covered by the caudal muscles (cp. Part II., fig. 4), this 

 conclusion receives some support. The gland is stated to have several openings in the 

 neighbourhood of the margin of the pore. Its function may be, as Burne suggests, 

 either to lubricate the pore during oviposition, or to occlude it by a waxy secretion, 

 and thus prevent access of foreign matter to the abdominal cavity. These suggestions, 

 however, disregard differences which should exist in relation to sex, and also the fact 

 that the genital pore is closed by the action of the sphincter cloaca\ I shall discuss 

 the alleged anal slime gland in a subsequent passage. 



The hind-gut has only a short course. It is easily distinguished from the mid-gut 

 by its sharp, acute, and somewhat irregular folds, which have no lymphoid packing, 

 and are similar to those of the fore-gut in having an epithelial investment of several 

 layers of cells. The lining of the cloaca even more resembles the epithelium of the 

 outer skin. 



I have already drawn attention (cp. Part I., p. 786) to the thin sheet of cartilage 

 described by Ayers and Jackson in the wall of the cloaca of Bdellostoma. I have 

 described in the section on the gut the only representative of cartilaginous tissue which 

 occurs in the cloacal region of Myxine. 



An original figure of the cloacal region and tail of Myxine glutinosa is given by 

 Goodrich in his masterly treatise on Fishes in Lankester's Zoology (p. 33). 



Since the above was written I have made and examined serial sections of the cloaca 

 of a 19-cm. and a 25-cm. Hag. In both cases the segmental duct expanded posteriorly 

 into a kind of sinus. From this expansion, which ends blindly behind, there is given 

 off internally another and terminal duct,* which at once bends mesially, dips urider 

 the sphincter cloacae, and, passing downwards and backwards, opens at the urinary 

 papilla as above described. Now the place where this terminal duct is given off 

 coincides precisely with the boundary between the mid- and hind-guts, and it is 

 therefore highly interesting to note : ( 1 ) that the lining of the segmental duct consists 



* A somewliat similar condition is figured by Burne in Bdellostoma. 



