78 EDWARD B. POULTON. 



observed, near the fungiform papillse, or indeed anywhere in 

 my sections, except in or around the area of the circumvallate 

 papillae. 



Mucous glands were, however, common in other parts and of 

 the type described (Klein, in the 'Atlas of Histology.*) 



The origin of taste bulbs. — This low form of bulb, found 

 upon the fungiform papillse, suggested to me a possible expla- 

 nation of the manner in which taste bulbs have arisen in Mam- 

 malia, At the outset it seems probable that in Marsupials or 

 Monotremes we have the best chance of finding the course fol- 

 lowed in the development of these and other structures, as we 

 know them in the higher mammals. 



For in these extremely ancient types, owing their existence 

 to isolation, with little rivalry to render structural advance and 

 complexity necessary in such forms, it is certain that long 

 halts will be made at stages long since left behind in the develop- 

 ment of other animals living on more warmly-contested areas. 



There is little doubt that the gustatory terminal organs have 

 more in common with those of the general surface of the bo.ly 

 than any other special sense. There is great structural resem- 

 blance, actual structural continuity, between skin and the oral 

 mucous membrane with its epithelium. Certain sensory ter- 

 minal organs are found in both, although it is probable that 

 they subserve the tactile rather than the gustatory sense in the 

 mouth. 



Before the appearance of taste bulbs actually opening on the 

 surface of the epithelium, when the gustatory surface was less 

 specialised, the terminal organs (similar to those of skin or 

 modified to receive at first feeble gustatory stimuli) would be 

 placed as in skin, namely, in the papillary upgrowths from the 

 mucous membrane. In this position they would be nearer to 

 the gustatory stitnuli than any other, without actual perforation 

 of the epithelium by the terminal organ, for, of course, the 

 layers of cells over a papillary process are far thinner than 

 elsewhere. It appears to me that then the serous glands were 

 modified from those of the general mucous type in the parts 

 where the terminal organs had been chiefly specialised. Simul- 



