l894-] NEW-YORK MICROSCOPICAL SOCIETY. 47 



then, of course, the protective hyaline tube disappears. Another 

 form of sensory organs are the end bulbs, which in Fishes serve 

 as tactile organs, but in higher forms develop into organs of taste. 



B. Amphibia. 



The skin of Amphibia, as in the Salamander, exemplifies a 

 transitionary stage from Fishes to Reptiles. Thus, in the aquatic 

 larval forms, two sharply differentiated layers of the epidermis can 

 be made out, the superficial one with that same striated cuticular 

 border which we find in Fishes (Fig. 2, S C). Later, with ad- 

 vancing development, the layers of the epidermis become more 

 numerous, involutions toward the derma take place to form a 

 great number of globular and tube-shaped glands (Fig. 2, 

 X, Y, N). This richness of glands is a marked feature of the 

 skin of Amphibia, and to it they owe their moist and slippery 

 nature. Their secretions serve a variety of purposes, from 

 merely supplying moisture, to a protective function in the form of 

 poison. 



Pigment is deposited in great quantities, partly in and partly 

 between the cells of the derma. Here, as in other forms, we see 

 that wonderful adaptation to environment, as exemplified in the 

 well-known green tree-frog and the sandy-colored horned toad of 

 our Western deserts. 



Calcifications may also occur in the derma, but they were more 

 abundant in fossil than in modern forms. Some of the integu- 

 mentary sense organs of this group have already been mentioned 

 in connection with those of Fishes. Another form, which is first 

 met with in the tailless Amphibia {Anura), is the tactile spot, con- 

 sisting of a group of cells in a typical form of papilla, which func- 

 tions as an organ of touch. 



C. Reptiles. 



In taking up this group for examination we notice two promi- 

 nent characters : the formation of scales and other horn-like 

 structures, and the almost total absence of integumentary glands. 

 Scales can here be dismissed with a few words. They are all 

 formed by a change in the epidermis, in which the derma takes 

 part later on. Many widely differing forms all originate in this 

 manner, and can be classed in general with the feathers of birds 



