338 PROFESSOR FRANK J. COLE 



should be noted that the constrictor cloacae, by enclosing the anus, genital pore, and 

 segmental ducts, will occlude all three at the same time. 



To add a still further note to the above, 1 have now, by the courtesy of Mr E. H. 

 BuRNE, examined his sections of the cloaca of Myxine. I find in the ureter that 

 the change from the single- to the many-layered epithelium occurs precisely as in my 

 own sections. The statement by Mr Burne, quoted above, that the epithelium changes 

 at the margin of the ureteric opening, is therefore incorrect. The only difference of 

 importance is that in Mr Burne's sections I find no glassy or granular mucous cells in 

 the terminal duct. These are, however, not numerous in my sections, and they may, 

 of course, disappear in the adult. With regard to the anal slime sac, Mr Burne has 

 been somewhat, and naturally, misled by not having examined sections of younger 

 material. The structure in question is undoubtedly what I have called above the 

 dorsal chamber of the cloaca, into which the genital pore opens, and the " semicircle 

 of openings " of the anal slime sac are simply the spaces between the folds into which 

 the lining of the cloaca generally is thrown. The dorsal chamber is naturally present 

 in my sections ; but, although it is crowded with the glassy and granular mucous cells, 

 it never occurred to me to identify it with Mr Burne's anal slime sac, since these cells 

 occur just as numerously in another region of the cloaca. I can, however, confirm 

 Mr Burne in one important respect, i.e. in the presence of the peculiar thread cells 

 in the dorsal chamber of the cloaca which are found elsewhere only in the lateral slime 

 sacs of the skin. Also the epithelium is crowded with the glassy raucous cells, but 

 there are no granular cells. In my preparations there are numerous granular cells, 

 but no thread cells. The slime sac character of the dorsal chamber of the cloaca 

 therefore develops late, and there is little doubt that the thread cells are produced by 

 modification of the granular cells. There is no occasion to conclude that the dorsal 

 chamber is a modified slime gland or glands. The whole skin produces glassy mucous 

 cells and thread cells of a type, as shown by G. Retzius, and the fact that the 

 slime sac characters have not been fully assumed in a 25-cm. Hag would indicate that 

 the conversion of the dorsal chamber of the cloaca into a kind of slime sac is a new and 

 independent feature. 



K. LITERATURE. 



[Li tliis list only those works are included which contain original observations on the viscera 



of Myxinoids.] 



(1) ABiLDGAAun, 1792. Schrift. d. Gea. nat. Freunde z. Berlin, Bd. x. pp. 193-200, Tab. IV. 



Naso-palatine opening, respiratory apparatus, gall bladder and liver, and mesentery of Myxine. 



(2) Allis, 1903. Anat. Anz., Bd. xxiii. p. 333. 



Gill clefts of Bdellostoma. 



(3) Aykrh, 1894. Biological Lectures delivered at Wood's Holt, 1893, vol. ii. pp. 137 and 152. 



Number and variation of Gills in Bdellostoma. 



