642 REPTILES AND AMPHIBIANS. 



Bennett* observe, can hardly be explained on tbe supposition that they 

 had passed through the larval state. It is probable, therefore, that as 

 the Salamandra atra, which lives high up the Alps, is ovoviviparous, and 

 Hylcdes marlinicensis, of Guadaloupe, f comes forth mature from the egg, 

 so our Amphibians, in part at least, under certain circumstances, bring 

 forth their young in a perfect condition. 



■ Again, physical agents exert an important influence upon the develop- 

 ments of the animals. Thus the larvae if kept in too deep water will not 

 develop. They grow, but continue in the tadpole state, unless the 

 liquid be shallow. Temperature also plays an important part, it having 

 been found that at 60° F. the ova of frogs will develop most rapidly, and 

 any diminution of temperature is followed by a corresponding retarda- 

 tion of development. The effect of light is rather a mooted question, 

 and yet it is probable, from the experiments of Edwards, Higginbottom J 

 and Thury,|| that its presence hastens and its absence retards their pro- 

 gress; the latter showing that in a green jar, with other conditions 

 equal, tadpoles would not develop, while they did in one constructed of 

 ordinary glass, thus rendering this conclusion highly probable. 



Some very recent interesting experiments are recorded on the Sala- 

 mandra atra, an ovoviviparous animal, by Madame von Chauvin,§ It 

 was believed that if the young were removed prematurely from the 

 mother and placed in water they would adapt themselves to an aquatic 

 life. The experiment proved entirely successful, in that one individual 

 lost its gills, developed a new pair suited to respiration, and, after four- 

 teen weeks residence in water, underwent transformation and became 

 a land Salamander. This would seem to indicate, that, at some not very 

 distant day, the Salamandra atra and maculosa had diverged from a com- 

 mon stock, and that while one continued on in its aquatic mode of re- 

 production, the other had, owing to changed conditions, become terres- 

 trial. 



As ?egards the geographical distribution of Reptiles, much might be 

 written, but a few facts will only be referred to here. That these ani- 

 mals, like the birds, increase in beauty and variety of markings, and in 

 their venomous properties as they approach the tropics, is an old observa- 



* Proc. Am. Ass. for Adv. Soi., 1853, p. 230. 



+ Am. Nataralist, vol. vili, p. 438. 



t Ann. and Mag. Nat. Hist., 3d Ser., vol. 15, p. 376. 



II Ibidem, 4th Ser., vol. 15, p. 376. See also Proc. Acad. Nat. Soi., 1867, p. 169. 



} Am. Natnralist, vol. xii, p. 468. 



