182 FIBST LESSONS IN ZOOLOGY. 



of the class. On the other hand, some were remarkably 

 like certain ganoid fishes, having gills and paddles, and 

 adapted for an aquatic life (Fig. 189). 



Thus the Amphibia connect in a degree the fishes and 

 reptiles, and show that these three classes arose like the 

 branches of a tree, from one and the same trunk. 



The salamanders, toads, and frogs are common in all 

 countries, temperate and tropical, and though those now 

 existing are but the dwarfed or modified representatives of 

 former ages, they occupy a place in nature which neither 

 fishes, on the one hand, nor reptiles, on the other, can fill. 



Works on Batkachians. 



Cope. Batracliia of North America. Bulletin U. S. Nat. Museum, 

 34, 1889. Witli the essays of Baird, Cope, etc. 



Mivart. The Common Frog. Nature, Science Series, 1874. 



Huxley and Martin. Practical Biology. 1889. (The chapter on 

 the Structure of the Frog.) 



Ecker. Anatomy of the Frog. Oxford, 1889. 



Ma/rshall. The Frog. 1891. 



Einehley. Notes on the Peeping Frog. Memoirs Best. Sec. Nat. 

 Hist., III. 1884. 



Oage. Life-history of the Vermillion-spotted Newt. American 

 Naturalist, Dec. 1891. Colored plate. 



Ola/rk. Development of Amblystoma punctatum. Pt. I. (Studies 

 from the Biological Laboratory of Johns Hopkins University, i. 1879.) 

 See also the treatises of Bamheke (1876), Moquin-Tando'" (1876), and 

 that of Scott and Osborn (1879). 



