3O6 INEZ WHIPPLE WILDER. 



exact nature is a problem. The usual explanation of the function 

 of the granular type of gland in the Amphibia is that its secretion 

 is of a poisonous nature and protects the animal from capture 

 by other forms which might use it as food. The full discharge 

 of the contents of the glands by the Desmognathus larva under 

 prolonged mechanical stimulation seems to corroborate this 

 explanation, as does also the special supply of these glands in 

 the region of those extremely important organs, the gills. On the 

 other hand, the enormous development which this type of gland 

 reaches in forms like Bufo and Plethodon, which have become very 

 terrestrial, seems to indicate a correlation, at least, with some 

 condition incident to terrestrial life, a conclusion further sub- 

 stantiated by the fact that the metamorphosis to the adult state 

 in Desmognathus involves the development of a great multitude 

 of glands of the granular type distributed over the entire surface 

 of the body, in place of the few isolated groups of such glands with 

 which the larva is supplied. Further, the fact that so closely 

 related a form as Spelerpes bilineatus does not possess such glands 

 while in the larval state leads one to ask what difference in 

 environment or habits of these two species could serve to explain 

 so decided a structural difference. We at once remember that 

 the most essential difference lies in the fact that Desmognathus 

 fusca is terrestrial in its egg laying habits while Spelerpes biline- 

 atus is aquatic, and that consequently there is no terrestrial 

 larval period in the latter species. Moreover, Spelerpes larvae 

 live in deeper pools than do the Desmognathus larvae, and so far 

 as I have observed, do not have the habit of lying upon leaves at 

 the very surface of the water, which is so characteristic a position 

 of the Desmognathus larvae, and one which brings out of the water 

 exactly those regions of the body which are supplied with the 

 acinous glands, the mid-dorsal region of the trunk and the slightly 

 elevated latero-dorsal surfaces of the head. Here again, then, 

 there seems to be a decided connection between exposure to air 

 and the function of the granular acinous glands. The solution 

 of the problem is one which can be made only after extended 

 experimental comparative study of different amphibians and 

 must therefore be postponed until such study is completed. 

 The other set of specialized integumental organs, the neuro- 



