1883.] TONGUES OF THE MARSUPIALS. 003 



some indication of such a separation in the presence of two kinds of 

 nuclei in the bulbs — the one spherical or oval, and the other greatly 

 elongated. The latter must belong to the central cells. To be 

 sure of this point, or indeed of anything in minute structure, the 

 fresh tissue should be examined. Considering, however, that these 

 structures in Halmaturus were not fresh, it would be hardly possible 

 to have obtained tissues in better condition for minute examination. 

 The question of the termination of nerves is better considered after the 

 description of the layers within the papilla. These are showu in fig. 

 XXI. Plate LV., which represents a transverse section through the 

 thickest part of a papilla. In the axis are the nonmedullated nerves, 

 which enter from below. They do not form any distinct ganglion 

 in the papilla (as in Perameles and Phalangista). In a few cases 

 isolated ganglion- cells were seen in the axis of the papilla, in one 

 instance at some considerable height. It is probable that the 

 ganglion-cells, which are always connected with the nerves of special 

 sense, form small ganglia on the nerve-branches near the base of the 

 papilla. The axial nerves are supported by trabeculae from the next 

 layer, and large blood-vessels are present, entering with the nerves. 

 The next layer, already mentioned, is derived from the dense mucosa, 

 and is composed of fibrous and possibly smooth muscular elements. 

 Blood-vessels are present in it ; and nerve-branches passing from the 

 axial nerves to the subepithelial layer may be seen streaming out- 

 ward through it. The next subepithelial layer is characteristic, not 

 occurring elsewhere. It represents the unravelled elements of the 

 two other layers united into interpenetrating networks. The impor- 

 tance of the layer is well seen by looking at the tissues underlyiuw 

 the ordinary epithehum, after looking at that beneath the bulbs. 

 Below the limits of the taste-bulbs the subepithelial layer thins away 

 abruptly, but its connective-tissue elements are probably continuous 

 with a delicate layer which lies between the deeper denser part of 

 the mucosa and the lowest layer of the epithelium on the outside 

 of the involution. The subepithelial layer disappears less rapidly 

 above the limits of the bulbs, and in some places its fine fibrils end 

 against the lowest epithelial cells. This is seen with especial clear- 

 ness in the cells of interpapillary processes ; and it may be that bulbs 

 are arising directly in this region, or (as is more probable) that these 

 masses of epithelial cells with the appearance of nerve-terminations 

 in them represent bulbs that have degenerated into the structures 

 from which they originally arose. This, however, is merely a sug- 

 gestion. Capillaries are present in this layer. At certain places 

 the subepithelial layer is converted into a tissue resembling adenoid 

 tissue, which may also invade the layer last described, sometimes 

 even reaching the axial nerves. A similar tissue has been described 

 in a corresponding position in the tongue of Omithorhynchus (see 

 paper on this subject by the present writer in the ' Quarterly Journal 

 of Microscopical Science' for July 1883). When the subepithelial 

 layer is studied under high powers (p^ oil-immersion of Zeiss), fine 

 fibrils are seen to terminate abruptly against the contour of the convex 

 lower surface of the bulb, separated only from the cells by the linear 



