94 SATURDAY LECTURES. 



stifif, and does not like to appear in society till he has thrown 

 off his old worn-out garments and put on new ones, never 

 hesitating about the fashion, but following the pattern of 

 his ancestors for generation upon generation. He begins by 

 pressing his elbows hard against his sides, and rubbing 

 downwards ; he keeps on until the skin on his back bursts, 

 and lie then works it into folds on his sides and hips. Now, 

 grasping one hind leg with Ijoth his hands, he hauls off one 

 leg of his pants, and there I almost before 3'ou can count 

 three, the other goes in the same wax. He now takes the 

 cast-off cuticle before him, between his legs, into his mouth 

 and swallows it, and even while it yet descends the gullet, 

 he has torn off the skin underneath, and brought it to his 

 fore legs or hands, and grasping one of these with the other, 

 by considerable pulling he strips them, just as we should 

 strip off a shirt, and by a single motion of the head he 

 draws the skin from the neck and swallows the whole with 

 a c-r-r-r-oak of satisfaction, for he knows full well, tliat such 

 a dainty morsel he can get but once a year. 



]Most frogs and toads go through the tadijole development 

 in the water, but in some terrestrial species where marshes 

 are scarce or lacking, the development takes place either 

 before birth or in a marsupium or sac on the back of the 

 parent. The tadpole state may also be indefinitely pro- 

 longed, as Jeffries Wyman kept one, of the bullfrog, for seven 

 years, or many more than the natural period of larval ex- 

 istence. The frog is a true vertebrate, belonging to the same 

 great Branch of the animal kingdom as man. Yet the 

 changes it undergoes after birth are as remarkable as are 

 those we have already noticed in the lower Branches. In 

 some allied animals, indeed, development is permanently 

 arrested in the tadpole .state, and I will, before passing to a 

 few well-known insects, briefly refer you to a rather re- 

 markable animal which occurs in our brackisli Western lakes 

 of high altitudes. I refer to it in order to show how greatly 

 form is influenced by conditions. Here we have figures of 

 it. (Fig. 8.) It was described b}' Prof Baird as Siredon 

 lichenoides, and, as you will note, has mauv of the character- 



