No. 2.] OiV THE GUSTATORY ORGANS. 157 



mucosa of the upper part and sides of the anterior papillae. In 

 the posterior papilla there are three or four tiers of bulbs. They 

 rest in depressions of the mucosa, and their apices traverse the 

 epithelium, but fail to penetrate its outer layers. They also 

 occur to some extent on the upper surface of the papilla. 

 Serous glands and ducts are present in the mucosa and sub- 

 mucosa, the latter being very plentiful. They open into the 

 trenches at their deeper part. No bulbs were detected either 

 in the fungiform papillae or epiglottis. No search was made for 

 the lateral gustatory organs. 



The Tongue of Pliascolomys wombat. 



This tongue (that of a young animal) had been kept in dilute 

 spirit, and was not in a very favorable condition for minute 

 examination. The hardening was completed in absolute alcohol. 



Gustatory Structures. 



The Circumvallate Papillce. — The papillae are arranged in 

 the usual triangle, the sides being a little shorter than the base. 

 Their summits are circular, or nearly so, and they are of nearly 

 equal size. They measure 0.75 mm. transversely, their height 

 being somewhat less. At their upper part they bear many sec- 

 ondary papillae ; below they are attached to the tongue by a 

 narrow pedicel. The trenches are narrow and uniform in width. 

 Serous glands are abundant, and their ducts discharge at the 

 usual places. 



The taste-bulbs are mainly restricted to the lower half of the 

 lateral walls of the papillae, although isolated ones not infre- 

 quently occur at higher levels. They are disposed in about ten 

 tiers, each tier containing on the average seventy closely packed 

 bulbs. They are also present in the epithelium of the outer 

 wall of the trench. Here they are disposed in five tiers. The 

 bulbs are long and narrow, and present considerable variation 

 in size. The mean length varies from 0.060 to 0.075 mm., and 

 the mean breadth from 0.024 to 0.035 mm. In a transverse 

 section through the centre of a bulb (0.030 mm. in diameter), 

 I counted some twenty-seven cells. In the subepithelial tissue 

 beneath the bulb region of the papillae is a rich nervous net- 

 work. From this network fibrils run to the bases of the bulbs 



