156 TUCKERMAN. [Vol. IV. 



The Lateral Gustatory Organs. — These organs are somewhat 

 rudimentary, and consist of five or six irregular folds of the 

 mucous membrane. The intervening furrows are narrow, and 

 vary in depth from 0.5 mm. to i mm. Serous glands are fairly 

 abundant, and their ducts discharge at the bottom of the fur- 

 rows. Sections through some regions of the organ show the 

 sides of the folds filled with bulbs, there being twenty or more 

 tiers of them. As a rule, however, they are fewer in number 

 and restricted to the lower half of the lateral area. They meas- 

 ure 0.046 mm. in length and 0.030 mm. in breadth. 



Bulbs were present at the upper part of the fungiform papillae. 

 In some sections as many as five could be counted, but they 

 were for the most part simple in structure, their apices failing 

 , to reach the superficial layers of the epithelium. They are very 

 small, averaging only about 0.030 mm. in length and 0.016 mm. 

 in breadth. 



In the young Didelphys the papillse and trenches, save in a 

 few instances, were undifferentiated. The glands and their 

 ducts were likewise incomplete in their development. The 

 bulbs were mainly epithelial in position and, as usual in em- 

 bryos and the new-born, had only dev^eloped at the upper part 

 of the papillae, the lateral area being destitute of them. One of 

 the more advanced among them measured 0.027 mm. in length 

 and 0.018 mm. in breadth. I failed to identify bulbs in the 

 epiglottis of Didelphys. 



The Tongue of Bettongia cimiculus ? 



This was the tongue of an embryo. It had been kept in 

 spirit. 



General Description. — The organ is long and narrow, and is 

 free for nearly half its length. The under surface is marked by 

 a longitudinal median ridge extending from the fraenum to the 

 tip, and the papillate surface is impressed anteriorly by a mesial 

 raphe. Fungiform papillae are freely distributed over the dor- 

 sum. The circumvallate papillae form a triangle near the base 

 of the organ. The anterior papillae could only be distinguished 

 with difficulty, their apices being barely visible within the nar- 

 row, slit-like openings of the trenches. The posterior papilla, 

 however, was clearly defined. 



There are some indications of bulbs in the epithelium and 



