602 MR. E. B. POULTON ON THE [DeC. 18, 



be drawn downwards from below, and this action alone would tend 

 to close the mouth. The dense mucosa (perhaps containing smooth 

 muscle- cells) which lies outside the epithelium of the involution is 

 invaginated into the papilla from below, forming a distinct layer in 

 it (to be described). Inside the papilla smooth muscle-cells may 

 exist in the invaginated mucosa. At the point where the mucosa 

 bends round to enter the papilla many striated muscle-fibres termi- 

 nate in it, their direction being vertical to the surface of the tongue. 

 Any contraction of these fibres must draw down the papilla, and 

 produce a tendency to close the mouth. It is possible, however, that 

 the tension produced by contraction acts also upon the mucosa outside 

 the involution, and thus tends to open the mouth. If this is the 

 case it is probable that closure of the mouth is rendered a specially 

 eflfective protection by the apex of the papilla being tightly clasped by 

 the contracting orifice (the papilla being raised valve-like against 

 the descending mouth by relaxation of the muscular contraction). 

 Conversely the papilla may be drawn downwards from below, and the 

 mouth opened by the same mechanism. It is only possible to decide 

 by experiment as to which action really takes place. It is in favour 

 of this view, that lateral compression of the fresh tongue causes a 

 descent of the papilla and an opening of the mouth in the similar 

 anterior papillae of Phalangista. Glands of serous type are extremely 

 abundant round these structures, and their ducts open into the space 

 between the involution and the papilla, at all heights, and not espe- 

 cially round the base of the papilla (the rule in higher types). 



The taste-bulbs are of the normal Marsupial type (as described in 

 a paper upon "The Tongue of Perameles nasuta" by the present 

 writer, in the ' Quarterly Journal of Microscopical Science ' for 

 January 1883), showing traces of their origin from the epithelial 

 cells of an interpapillary process, in the indications of papillae between 

 the bulbs, and in the fact that the cells do not converge into a distinct 

 basal pole. I was never able to detect indications of the protru- 

 sion of any structures through the gustatory pores. In order to be 

 certaiii of the absence of such delicate processes (described in the 

 higher mammals) the fresh tissue should be examined; but upon the 

 whole I am inclined to think that such structures are absent from 

 the bulbs of Marsupials, which are less specialized than those of 

 the higher forms in the above-mentioned points. I have examined 

 so many hundreds of distinct pores and bulbs with the cells appa- 

 rently perfect, in so many species, that I believe some trace of 

 these structures would have been detected if they were present. 

 The gustatory pores are very short, only penetrating a thin super- 

 ficial corneous lamina of the epithelium, which easily splits away 

 from the rest. Very often the epithelial cells below the thin lamina 

 split away with the latter, thus rendering the dome-like coverings of 

 the taste-bulbs very distinct. The same layers tend to split away 

 from the wall of the involution in which the papilla is contained. 

 It is probable that the bulbs present a less marked separation than 

 is met with in higher mammals, into peripheral protective cells 

 and central cells which are nervous end-organs. But there is 



