Siredon into Amblystoma. 373 
tat, regards it as probably permanently aquatic.+ In the ele- 
vated region where Lake Como is situated, although the 
upon the later, of even slight differences of physical conditions, 
as shown in the preceding instances, are known to produc 
When combined remarkable variations in the same os as 
reaso cannot for various 
th; ns be discussed in this connection, but it is evident that in 
is direction lies a rich field for further investigation. The 
seems have sus- 
pectedi—that all Siredons are merely larval Salamanders, and 
' Perennibranchiates (by no means a natural division of 
© Batrachia) may not prove eventually to be the undevel- 
oped young of well known species. ; 
In addition to the acknowledgments already made, the writer 
* Pacific R. R. Report, vol. xii, part 2, p. 306. t Loe, eit. 
+ Recherches tial tase Ma Reptiles, rie Paris, 1807, p. 35. 
