56 ELEMENTARY ZOOLOGY 



older the appearance of eyes, the shrivelling of the gills, 

 shrinking of the tail and development of legs ; in the still 

 older the characteristic shape, in miniature, of the adult 

 toad. 



In observing the course of development of the living 

 specimens there should be made, in addition to the draw- 

 ings, notes showing the duration of the egg stage, and 

 the time elapsing between all important changes (as seen 

 externally) in the body of the young. Observations and 

 notes on the general behavior of tadpoles should also be 

 made ; note the swimming, the feeding, the gradual leav- 

 ing of the water, etc. 



In addition to the easily seen external changes in the 

 body, very important ones in the internal organs take 

 place during development. Perhaps the most important 

 of these concerns the lungs. The young gilled toad 

 breathes as a fish does, but gradually its gills are lost, 

 while at the same time lungs develop and the tadpole 

 comes to the surface to breathe air like any lunged aquatic 

 animal. The toad on leaving the water changes its diet 

 from vegetable to animal food ; a tadpole feeds on aquatic 

 algae; a toad preys on insects. Correlated with the 

 change in habit, the intestine during development under- 

 goes some marked changes, becoming relatively dimin- 

 ished in length. 



For an account of the development of the toad see 

 Gage's "Life-history of a Toad" or Hodge's "The 

 Common Toad. ' 



