" POEUS GENITALIS " IN THE MTXINIDiE. 489 



{Fetromyzon marinus aud fiuviatilis) ; but, as his descriptiou 

 applies to the river form alone, one cannot avoid the suspicion 

 that, although he may have cursorily examined P. ^narinus, his 

 real observations were confined to P.Jluviatills. Ewart does not 

 in his paper mention the species of Lamprey used, but through 

 the kindness of my friend Professor Howes, E.E.S., I have 

 ascertained that it was P. marinus; a coQcIusion to which I had 

 been led by a comparison of his description with a dissection of 

 that species. In this way the conflicting statements appear to 

 admit of explanation. Then, again, with reference to the opening 

 of the ureters into the uro-genital sinus, it should perhaps be 

 more emphatically mentioned that the passage of the one into 

 the other is gradual and imperceptible ; the ureters, in fact, meet 

 in the mid-line, coalesce and dilate to form the sinus ; there is no 

 papilla or any other mark to show where the one ends and the 

 other begins. 



As concerns Myxine glutinosa, in which the " pori genitales " 

 are described as essentially similar to those of the Lamprey, I 

 find a very different state of affairs, of which the following is a 

 description (fig. 1) based upon the dissection of six specimens, 

 checked by the examination of a series of transverse sections 

 through a seventh *. 



When the creature is placed upon its back, the mouth of the 

 cloaca has the appearance of a narrow longitudinal slit some 

 10 mm. long, bordered by somewhat protuberant lips. The slit 

 leads into a small chamber (fig. 1, cl.) flattened from side to side, 

 and having roughly the form of an isosceles triangle placed iu 

 such a position that one of its sides corresponds to the cloacal 

 slit and its short base to the anterior wall of the cloacal chamber. 

 In the walls of this chamber there are four openings : two, of 

 large size, in the anterior wall placed vertically one above the 

 other, the anus below and the genital pore above (fig. 1, an. 

 p.g.) ; and a smaller pair belonging to the ureters, situated close 

 side by side on a papilla halfway along the dorsal wall (fig. 1 

 ur.o.). The dorsal and lateral walls of the cloacal chamber are 

 raised into several longitudinal ridges that can be separated into 

 a lower series continuous with the rectal rugse, and an upper 

 originating from the margin of the pore. Between these two 



* These specimens of Myxine glutinosa were obtained from the Bergen 

 Museum for the Eoyal College of Surgeons, some preserved in spirit, some 

 in formalin. 



