1 84 THE AMERICAN MUSEUM JOURNAL 



TOADS AND FROGS. 



Order Salientia. 



The Toads and Frogs are the most famiHar forms of the 

 batrachians. Eleven species occur in the local fauna, repre- 

 senting four families. All of the local species deposit their eggs 

 in the water and the young pass through a tadpole stage before 

 acquiring the form of the adult. The duration of this larval 

 stage varies considerably with the different species. In some 

 it is limited to a few weeks, others require considerably more 

 than a year to complete their metamorphosis. The growth in 

 the water is much influenced by light and temperature. 



For a short time after hatching, the tadpoles of most species 

 are provided on the under surface of the head with two suckers. 

 These organs enable the fragile creatures to cling to the leaves of 

 aquatic plants instead of lying upon the muddy bottom, where 

 they would be exposed to the attacks of many enemies in the 

 shape of the carnivorous larvse of aquatic insects. At the time 

 of hatching, the young creatures are leech-like in appearance. 

 Development is rapid. Within three days they present the 

 complete form of the tadpole, with fin-like tail. Within a few 

 hours after hatching the mouth-parts begin to develop, and a 

 few days later the little creature feeds upon delicate aquatic 

 vegetation. They then swim readily in search of food, and the 

 suckers become aborted and quickly disappear. 



For a f ev/ hours after leaving the egg, the frog tadpole possesses 

 branching gills. These soon shrivel and their bases are covered 

 with folds of skin (the "operculum"). Under this fold the fore 

 limbs soon begin their growth. This is the first pair of limbs to 

 acquire full growth, but they are not visible until after the hind 

 pair has appeared. From external appearances the frog tad- 

 pole thus seems to acquire the posterior pair of limbs first. 

 Somewhat later the front pair suddenly are thrust through the 



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