THE BATRACHIA OF NORTH AMERICA. 



49 



The experiiueuts of Hogy, above alluded to^ are as follows, as given 

 by liiiu iu the Annals and Magazine of Natural History. 



He placed a number of impregnated ova of frogs in vessels arranged at 

 regular distances from the liglit in a cave. The lessening degrees of 

 light were of course accompanied by a corresponding but much less 

 rapid decline in temperature. The resulting effects on the metamorpho- 

 sis may be tabulated as follows : 



^ 



cS 

 P 



11 



20 

 25 

 81 

 10 

 22 



11 



28 



31 



Mean, Fahrenboit. 



a 



O 



3 



00° 



56° 



53° 



51° 



3 



Egg 



Larva free 



Egg 



E'-^g 



Egg. 











Laiva free 



Larva free 







Larva very large 



Metamorphosis com - 

 plete. 





4 



Larva largo 



Motamorpliosis com- 

 plete. 











8 











Metamorphosis com 

 plete. 



i 



10 







Metamorphosis com- 

 plete. 











Other experiments, which will not be quoted now, are equally con- 

 clusive as to the effects of light and heat on their process. The dis- 

 tinction between maturity, or adult age, and complete development 

 must be borne in mind. The former condition is attained when the ova 

 are fitted for impregnation and the spermatozooids are capable of accom- 

 plishing that result. Development may or may not advance much 

 beyond this period. As one or more periods in the life of every species 

 is characterized by a greater rapidity of development (or metamorpho- 

 sis) than the remainder, so in proportion to the approximation of such 

 a period to the epoch of maturity or reproduction is the offspring liable 

 to variation. 



The great difference between the different species and between indi- 

 viduals of the same species iu this respect, may be illustrated by the 

 following comparison between the size of the animals at the time of 

 losing the branchia?-, so far as known, and that to which they nlti- 

 mately attained : 



Species. 



Amhlystoma jefforsonianum 



Amblystoma puuctatiim 



Aiublystoma conspersum . . . 



Amblystoma opacum 



Chomirotiis texanus 



Choudrotus microstomus . . . 



Amblystoma talpoideum 



Choudrotus paroticus 



A mhlystoma tigrinum 



Choudrotus tenebrosus 



Siito at 



loss of 



braiichiic. 



3* 

 3 



\l 



Average 

 full size. 



10 



10. r. 

 1 



3.5 



7.5 



7t 



9.5 



6 



9 



In. Lin. 

 G 

 G 



2 7.5 



3 0.5 



9.5 

 2.5 



1951- 



* Perhaps too largo. 



-Bull 34 4. 



f Not smallest. 



