374 CLASSIFICATIONS OF THE AMPHIBIA. 



other amphibians which have changed their forms; conse- 

 quently, from these comparisons I feel tolerably confident, 

 that some use of those permanent organs, in the animals now 

 under notice, may be derived by them in the function of re- 

 spiration whilst in water ; although satisfactory proofs of this 

 supposition can only be established by future experiments, 

 to be made for the express purpose of investigating that im- 

 portant question. The third order comprehends a single 

 family, which I have named Menopomatidm, by taking the 

 appropriate title of the genus Menopoma 1 for its type. 



The retention of external branchial tufts or ramified gills, 

 with permanent hyoidean arcs, and mostly with lids or oper- 

 cles, is distinctly intended by the word that denotes this last 

 order, — Manentibranchia. 



The two families I have distinguished principally by the 

 form of the body and the number of the legs. The genera 

 will exhibit (among other marks) the variations in the num- 

 ber of toes. 



The comparative naturalist will here with pleasure consider, 

 how the steps in the gradation of the different respiratory sys- 

 tems, among the higher classes of the animal kingdom, are 

 nicely and beautifully varied ; how inimitably and gradually 

 they lead from the most complete to the inferior development ; 

 and how the transition from a perfect pulmonary respiration 

 to a perfect branchial one, is gently, and not instantaneously, 

 effected. For in the Mammalia, birds, and reptiles, there are 

 lungs more or less perfect ; in the Amphibia there exist, first, 

 well-formed lungs without gills ; — secondly, at first perfect 

 gills and no lungs, afterwards lungs without gills ; — thirdly, 

 imperfect gills co-existing with lungs ; —fourthly, perfect gills 

 with less-developed lungs ; — and lastly, in the fishes, most 

 complete gills, but lungs entirely wanting. 



If, however, it should be hereafter found, that the gill-like 

 organs in the Alenopomatidce are in reality gills, or merely a 



in pi. 5 of Rusconi's f Amours, ' with the Amphiuma means, fig. 7 of the 

 same plate : also examine the preparation of the Surinam toad, No. 917 A, 

 in the Museum of the Royal College of Surgeons. 



1 Dr. Harlan hestowed that appellation on this genus, because the oper. 

 cula are persistent : it is derived from ft-svco, maneo, and Tra/xa, operculum. 



With regard to the name of the second genus, Dr. Wagler observes, — 

 "der sippename Amphiuma wird wohl verandert werden miissen. Was soil 

 Amphiuma heissen ? " The generic name well deserves to be changed. — 

 What does Amphiuma signify ? I conclude that it is derived from a/Mfpi, 

 circa, and v(Aa for v<rfj,a, pluvia; — circa pluviam, i. e. aquam habitans, — 

 from its frequenting pools left by the rain and other waters. 



