The Zoologist— March, 1869. 1579 



noticed by Dr. Suckley,* but that they can remain out of water for 

 several days is a new and important fact, showing that even before 

 metamorphosis the lungs are sufficiently developed to sustain life 

 without tlie aid of branchial or dermal respiration. 



Whether this species of siredon ever changes at Lake Como, and in 

 other similar regions, is an interesting question, and one that cannot, 

 perhaps, at present, be answered with certainty. That it does so 

 occasionally, however, under favorable circumstances, especially when 

 young, several facts known to the writer would seem to indicate, 

 although Dr. Suckley, one of the few observers who have hitherto 

 examined it in its habitat, regards it as probably permanently aquatic. t 

 In the elevated region where Lake Como is situated, although the 

 weather in summer is quite warm, the nights ai'e always cool, and the 

 changes of temperature often sudden and very great ; hence the meta- 

 morphosis, if it began, would probably proceed slowly, and be liable 

 to suspensions during its various stages. That the species, however, 

 breeds in the siredon state, like the Mexican axolotl, there can be 

 little doubt, although direct evidence on this point appears to be 

 wanting. The observations of Dunieril, already alluded to, and other 

 similar facts, render it probable that after reproduction the power of 

 complete development would be lost, although alterations in colour 

 and other minor changes might still occur. 



The near approximation in many Batrachians of the periods of 

 reproduction and metamorphosis, and the effects, especially upon the 

 latter, of even slight differences of physical conditions, as shown in the 

 preceding instances, are known to produce when combined remarkable 

 variations in the same species, as well as other results until recently 

 quite unexpected. The bearing of these and similar facts on a theory 

 of development, although an inviting topic to enter upon, cannot, for 

 various reasons, be discussed in this connection, but it is evident that 

 in this direction lies a rich field for further investigation. The obser- 

 vations here recorded, however, when taken in connection with those 

 of Dumeril on the Mexican axolotl, render it extremely probable — as 

 Cuvier long ago seems to have suspected J — that all siredons are 

 merely larval salamanders, and also suggests a doubt whether some, at 

 least, of the other so-called Perennibranehiates (by no means a natural 



* Pacific RHilroad Report, vol. xii., part 2, p. 306. 



f Loc. cit. 



X Rechcruhes anat. sur les Reptiles, &c., Paris, 1807, ji. So. 



