Anatomy of Notoryctes typhlops. 91 



full of secretion. From this, as from the large size of the Organ, 

 we may perhaps infer that in Notoryctes the glandular function 

 is relatively more important than the sensory one. 



Coming down from the side of the septum, and running longi- 

 tudinally, are a small nuniVjer of scattered nerve fibres similar to 

 those described by Klein in the Rabbit.^ 



The main features of the histology also agree closely with those 

 described by Symington in Macropodidae.* 



2. — Median Wall. 



The sensory epithelium lining this wall (Fig. 6, m.m.) 

 extends also as described in the Guinea-pig by Klein^ in the 

 anterior half, a short distance down the lateral wall of the 

 superior sulcus, but ending at the angle of the inferior sulcus 

 for the whole length. Its thickness varies from .08 to .1 mm., 

 slightly greater than in Dog, and slightly less than the Guinea- 

 pig. In the posterior part the sensory epithelium ends also at 

 the angle of the superior sulcus. The boundary between the 

 epithelium of the lateral wall and the sensory epithelium of the 

 median wall is always very sharply marked otf. 



The sen.sory epithelium in Notoryctes resembles closely in its 

 general structure that of the Guinea-pig,* Rabbit^ and Dog,* 

 though the minute structure of the cells cannot be made out in 

 these spirit specimens. The epithelial cells which bear short 

 cilia appear much longer and thinner than those of the lateral 

 wall, and have a striated border, probably due to the terminal 

 rods of the cells in the lower layer. These epithelial cells have 

 oval nuclei, which are disposed in three ill-defined layers similarly 

 to the above mentioned forms. The sensory cells have large 

 spherical nuclei more transparent and less deeply staining with 

 haematoxylin, and with a well-marked nuclear membrane and 

 network. They are arranged in one or two layers (as in the 

 Dog), usually in one layer near the upper and lower sulci, and 

 tw(t layers in the median part of the wall. In one or two places 



1 Q.J.M S., vol. xxi., pp. 556, 564. 



2 Jour. Anat. and Phys., vol. xxvi., p. 373. 



3 Q.J.M.S., vol. xxi., p. 105-6. 

 i Loc. cit., p. 564, etc. 



5 Loc. cit., vol. xxii., p. 307-310. 



