ON THE GENERAL MORPHOLOOY OF THE MYXINOID FISHES. 313 



mediate region," which may be entirely closed by the constrictor muscle [constrictor 

 cardiie], the granular cells become rare and finally disappear, the slime cells are reduced 

 in number, and the superficial cells again give the slime reaction as in the mouth. 



Haack, who appears to be unaware of Maas' paper on the gut of Myxine, states 

 correctly that the multicellular oral gland of the lamprey is not present in Myxine. 

 He criticises Schreiner's paper as regards some of the smaller detail, and finds no 

 transverse folds in the pharyngeal gut, as I do. He regards the gut up to the 

 beginning of the gills as corresponding to the pharynx of Petromyzon. My prepara- 

 tions agree with his in one respect — that the granular cells do not contain a continuous 

 thread, as described by Schreiner. They do not, however, always contain the thread 

 in the outer skin. He compares the granular cells with the gland cells in the 

 oesophagus of the Ammocoete. 



The nasal tube is surrounded more or less by an extensive lymphatic sinus situated 

 between the nasal rings and the tube itself. The epithelium is many-layered and rests 

 on a distinct basement membrane. Under that there is a dense fibrous vascular 

 connective tissue which diminishes posteriorly. The superficial cells of the epithelium 

 give the mucin reaction. The glassy mucous cells are very numerous and larger than 

 those in the skin, but the granular cells are scarce and quite small. 



There are no mucous cells in the olfactory laminae of the nose, although they are 

 still present in the ventral non-olfactory portion of the tube, the epithelium of which 

 is so thin that the mucous cells not only occupy its entire height, but project beyond 

 it into the lumen of the nasal chamber. 



In the naso-pliaryngeal tube the epithelium is very thin but many-layered, and 

 there is a definite basement membrane. The glassy mucous cells are very numerous, 

 but only a few of the superficial cells give the mucin reaction. The discharging glassy 

 cells project markedly into the lumen of the tube, and often at the other end rest on 

 the basement membrane. There are numerous granular cells in the posterior section of 

 the tube, especially in the region of its opening. Next the epithelium is some very 

 loose vascular connective tissue, which posteriorly becomes fibrous, and then follows 

 the lymph sinus. 



The epithelium of the mouth near the opening is many-layered, and rests on a dense 

 fibrous connective tissue. There is no difi"erentiated free border. The three or four 

 superficial layers of cells give the mucin reaction, and their nuclei are pushed to one 

 end of the cell. The glassy mucous cells are numerous and large, but there are no 

 granular cells, nor any multicellular glands. There are no mucous cells in the 

 immediate neighbourhood of the teeth, and in fact the number of these cells is reduced 

 in this region, the lateral epithelium further being here very thin, but containing 

 raucous cells. 



At about the region where the naso-pharyngeal tube opens into the mouth, i.e. 

 opposite the anterior extremity of the notochcord (cp. fig. 1), large numbers of the 

 granular mucous cells appear in the epithelium, similar to those in the skin, but 



