TONGUE OF OrvNITlIORHYNOlIUS PARADOXUS. 469 



glion cells, while some are spherical. In all the nuclei are 

 very distinct, and the elements, as a whole, differ from the sur- 

 rounding epithelium in staining much more deeply, and in their 

 loose, irregular arrangement. If the looseness is due to shrink- 

 ing this proves a difference of structure, as the epithelial cells, 

 exposed to the same conditions, have not shrunk away from one 

 another. The nerve-fibres enter the bulb, and do not terminate 

 in a group at the basal pole in the usual way, but are seen 

 running between the cells of the bulb in various places. 



There is more certainty of the nerve- fibres passing to each 

 bulb in this case, with the easily found papillary upgrowth as 

 a guide to the bulb, and containing its special fasciculus of 

 nerve-fibres. I was enabled by teasing to isolate one undoubted 

 terminal cell with the nerve-fibril still attached to it. It is 

 shown in fig. 14, and the fibril is seen to branch before termi- 

 nation. The shape is very simple and fusiform, with no peri- 

 pheral process. There are traces of a nucleus and of an axial 

 line continued from it along the cell. The general appearance 

 of a bulb is shown in fig. lo, in which the elements are seen to be 

 separated by considerable intervals, probably due to shrinkage. 

 There is no doubt that the epithelium has been penetrated by 

 the bulb, and not merely reflected over it. This is proved by 

 the non-continuity of the lowest layer of columnar cells over 

 the bulb (fig. 13). But this intrusion of the bulb does not 

 mean, as in other mammals, that the elements are formed from 

 the modified epithelial cells, although these may be present. 

 A further conclusive proof that the bulb is essentially subepi- 

 thelial in nature is found in the fact that isolated bulbs in the 

 abnormal and rudimentary left posterior organ occur beneath 

 the epithelium, others partially embedded in it, and others, 

 again, arranged in the usual manner with gustatory pores. 



This peculiar form of bulb has an important bearing upon a 

 theory as to the origin of taste-bulbs suggested by me in the 

 January number of this Journal (the " Tongue of Perameles"). 



The Origin of Taste-bulbs. — From observations upon 

 the tongue of Perameles I was led to infer that the usual 

 mammalian bulb was developed from a group of interpapillary 



