1883.] TONGUES OF THE MARSUPIALS. 605 



mucous glands, although some of the lobules appear to be serous. 

 No bulbs are present in the walls of these ducts. The epithelium 

 round the lateral organs (and that of all the non-papillate surface I 

 examined) is of the dense complex kind, similar to that described in 

 the tongue of Omithorhynchus (in the paper previously referred to). 

 In such an epithelium four distinct layers can be made out. By far 

 the thickest of these is the lowest layer, which presents all the 

 characters of the rete Malpighii, staining deeply below, slightly 

 above ; over this is a thin layer of cells that stain deeply in most 

 reagents, and possess very long thin nuclei (in vertical sections) : 

 above this is a layer of aljout equal thickness, behaving toward 

 reagents in the same manner as corneous cells ; this again is followed 

 by a thicker, deeply staining layer of fusiform cells v?ith distinct 

 elongated nuclei. The remarkable thing about this epithelium (as 

 was pointed out in describing the tongue of Ornithorhrjnchus) is that, 

 in upward succession, cells presenting the characters of a corneous 

 layer should again come to present the characters of non-corneous 

 epithelium (see fig. xxxi. Plate LV.). A hair was seen in one section 

 of a lateral organ; and probably due to the irritation caused by it, 

 the mucosa beneath was crowded with large deeply staining cells. 



C. Fungiform Papillce. — The same imperfect type of bulb is seen 

 on the summit of these papillae that has been described in the same 

 situation in Perameles (paper previously mentioned). Such bulbs 

 show more distinct traces of their origin from interpapillary epithelial 

 cells than those in any other part of the tongue. Their appearance 

 upon these papillae is probably very recent, and it is noteworthy that 

 this is the only instance of their occurrence without the immediate 

 proximity of serous glands. Large non-medullated nerves are found 

 in the axis of the papilla. Beneath the bulbs the subepithelial 

 layer is distinct. Gustatory pores are present, and as many as 

 six bulbs can be seen in a single section of one papilla. It is not 

 unlikely that these papillae are tactile (they are tactile in Omitho- 

 rhynchus, and if gustatory here, the change is recent). 



II. Mechanical and Tactile Structures. 



A. The Coronate Papilla. — These are of the usual Marsupial type, 

 much resembling the same papillae in Perameles (described in the 

 paper alluded to). Horizontal sections at successively higher levels 

 show that the main papillary upgrowth is at first irregular in shape, 

 then horseshoe-shaped (the concavity anterior) with the arms 

 gradually breaking up into the separate papillary upgrowths for the 

 secondary papillae. Hence the posterior side of any such section 

 can be known at a glance, because here the secondary processes 

 arise at a higher level, and therefore some of them have not yet 

 separated from the main upgrowth. (See fig. xxviii. Plate LV.) 

 If the section is taken sufficiently high to show a complete ring of 

 secondary papillary processes, it is still easy to know the posterior 

 side, because posteriorly the processes are cut through at a lower level. 

 (This is rendered clear by fig. xxvi. Plate LV., which shows a sinu;le 

 coronate papilla of Mucrojnis in perspective.) 



Proc. ZooL. Soc— 1883, No. XL. 40 



