640 REPTILES AND AMPHIBIANS. 



only by diminishing its cavities but by expanding its own. In this 

 manner the deep meshes sometimes appear white while the exterior net- 

 work takes on a pearly aspect. The animal in this manner, by blend- 

 ing in a different degree two or three primitive colors, changes its shade 

 so much that it comes to resemble the object upon which it happens to 

 be. A similar power to vary these colors at will is present to a greater or 

 less extent in all the Hylidse. The advantages of this, in enabling these 

 animals to escape their enemies, and to approach their prey unobserved, 

 is too obvious to be considered here. 



In this connection it may be mentioned, that tadpoles sometimes show 

 a mimetic coloring. A case of this kind is recorded by Miss Monk,* 

 in which, being kept in an aquarium with Water Purslane, Ludwidgia 

 palustris, they imitated almost precisely the color of the leaves. So per- 

 fect was the resemblance that a friend visiting her was actually deceived 

 and mistook a leaf for a tadpole. Personally I have seen such cases of imi- 

 tation, but none sufficiently marked to justify a person being misled in 

 this manner. 



Again, the serpents have a remarkable power of enlarging their 

 bodies by the inhalation of air. To understand how this is done it is but 

 necessary to dissect a snake, and observe the situation and length of the 

 lungs. By thus enlarging his body the serpent renders himself more 

 formidable in appearance, and has thus a tendency to frighten away an 

 enemy. Add to this the peculiar blowing sound with which the air is 

 emitted, sometimes as in Hetewdon, suggesting the rattle of the Crotalidx, 

 and again, as in Pityophis, said to imitate the roaring of a bull, and this 

 matter of exhalation, as well as inhalation, has a profound significance. 



Another mode of protection is in the secretion of some of these ani- 

 mals. Thus the frog on being caught usually ejects a quantity of fluid, 

 and also becomes more or less swollen. The use of this ejection was to 

 me a mystery until seeing Mr. Aldrick's f account of a snake gliding 

 upon a frog, when the latter simultaneously jumped and threw this 

 liquid into the mouth and eyes of the serpent. The latter was ap- 

 parently blinded by the discharge, sprung wildly from side to side, and 

 lost track of his intended prey. This incident seems to indicate that the 

 ejection of this fluid in the frog accomplishes the same purposes as the 

 discharges in the Bombardier Beetles, and enables the Batrachian to 

 escape its enemies. 



However this may be, the cutaneous secretions of some Reptiles, 

 and Amphibians are admirably adapted to the purpose of protection. 



*Am. Naturalist, vo), xii, p. 695. 

 i Am. Natnralist, vol. xii, p. 473. 



