| OCR Text |
Show 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 Ornithorhynchus (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 about 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 with distinct elongated nuclei. The remarkable thing about this epithelium (as was pointed out in describing the tongue of Ornithorhynchus) 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 Papilla.-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 Ornithorhynchus, and if gustatory here, the change is recent). II. Mechanical and Tactile Stimctures. 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 single coronate papilla of Macropus in perspective.) PROC. ZOOL. Soc-1883, No. XL. 40 |
