488 ME. E. H. BTJENE ON THE 



part dealt with the related family of tlie Lampreys, or contented 

 themselves with a summary of Miiller's original description of 

 Myocine glutinosa. An exception must be made, however, in 

 favour of Ewart *, for, at the end of a paper on the genital pores 

 and surrounding parts of the Lamprey, he devotes a few lines of 

 original description to the same organs in Myxine. Yet, on 

 the whole, our present information upon this subject is so scanty 

 and, as will appear later, inaccurate, that I venture to put 

 forward the following brief description and drawings of the 

 anatomy of the cloacal region in Myxine glutinosa and Sdello- 

 stoma cirrhatum, in the hope that they may form an appendix to 

 the excellent description given by Ewart of these parts in the 

 Lamprey. 



According to Ewai-t, " the intestine of the Lamprey is a straight 

 tube which lies free in the abdominal cavity, except near its termi- 

 nation, where several fine bands — the remains of the mesentery — 

 fix it to the under surface of the notochord." The body-cavity, 

 after the intestine has reached the ventral body-wall on its way 

 to the anus, is continued on either side in the form of a blunt 

 cone, near the apex of which a small aperture leads into a 

 pyriform chamber (the uro-genital sinus). The base of the uro- 

 genital sinus is in open connection with the ureters, and the apex 

 projects freely into an integumentary pit, into which it opens 

 close behind the anus. Thus we have a pair of internal " pori 

 genitales " opening on either side from the body-cavity into a 

 uro-genital sinus, and a single median external pore opening 

 from the latter into the clcaca. Such appear to be the essential 

 features of Ewart's description ; but before leaving the Lamprey 

 there are two minor points upon which I would comment. 

 Ewart makes a great feature of the blunt ending of the body- 

 cavity and its backward extension (1 line) beyond the " genital 

 pores," and infers therefrom an error of observation on the part 

 of Miiller, who speaks of the " genital pores " having the form of 

 a pair of tubes, one on either side of the rectum, that open at 

 their ends into the uro-genital sinus. An examination of the 

 cloacal region in the Eiver Lamprey suggested to me that 

 the discrepancy between these two accounts might very possibly 

 be due to the description of a diftereut species in either case. 

 Miiller, we know, examined both the Sea and Eiver Lamprey 



* J. C. Ewart, " Note on the Abdominal Pores and Uro-genital Sinus in the 

 Lamprey," Journ. Anat. and Phys. x., 1876. jd. 493. 



