AMPHIBIA 251 



breed. It lays its eggs in little packets under logs and 

 stones, and guards them until they hatch. 



Considering the ontogeny of salamanders and the habits 

 of various existing species, the law of biogenesis (page 60) 

 indicates that they are as a group migrating from water 

 to land. Nearly all begin life as a fish-like tadpole which 

 breathes by means of gills, but in the adult condition there 

 are all degrees of adjustment to terrestrial life. 



THE COMMON TOAD, Bufo americanus Le Conte 



Salientians in general are highly specialized. They start 

 in life as tadpoles, but are tailless when mature and show 

 many evidences of specialization. The toad is a typical 

 representative. It is specialized in its marked adjustment 

 to terrestrial life, but shows aquatic affinities in its habit 

 of annually returning to the water to breed. 



Self -maintenance. A toad obtains food by means of 

 its flexible tongue. There is a gland in the roof of the 

 mouth which forms a very sticky secretion. When the 

 tongue is suddenly protruded, it adheres to the food and 

 draws the morsel back into the mouth (Fig. 98, B). The 

 tongue is extended by suddenly filling a lymph space at 

 its base. Toads depend chiefly on their sense of sight for 

 procuring food and will snap at almost any moving object. 

 This habit is general among salientians, and is taken ad- 

 vantage of by fishermen who use a bright-colored rag as 

 bait for catching frogs. A toad has no teeth and insects 

 captured are swallowed at once without any preliminary 

 chewing. If some distasteful object is snapped up, it is 

 quickly spit out, even after it has passed down into the 

 stomach. 



The food habits of toads make them of considerable 

 economic importance. A recent estimate by a scientific 

 expert in the Department of Agriculture places the annual 

 value of a single individual in a garden at $19.44. In cities 

 also a toad may do great good by feeding at night on the 

 insects about street lights. 



