18 University of California Publications in Zoology [Vol. 27 
trial in all stages of their existence, and one form, Aneides lugubris, 
conducts its spawning operations in the arboreal habitat of damp holes 
in oak trees. 
In California, no one locality, save perhaps in the extreme north- 
ern part of the State along the Oregon boundary, supports more than 
two species of frogs. Only two ecologic types are represented, a pond 
type {aurora) and a stream type ( boylii ). Farther north, in Oregon, 
two pond or marsh types are found ( aurora and pretiosa ) ; but the 
stream type ( boylii ) is not found beyond southwestern Oregon. Pos- 
sibly the presence of Ascaphus truei excludes Rana boylii by way of 
competition in the northern streams. In the eastern states as many 
as five species of frogs, each with a particular ecologic preference, may 
be found in one locality (see Wright, 1914). Comparing other groups 
than the amphibians we find that the fish fauna of the northeastern 
United States consists of a large number of species, each with a special 
ecologic preference. In California the fish fauna even of one of our 
large rivers comprises a relatively small number of species. For 
example, the total native fresh-water fish fauna of the entire Sacra- 
mento basin is about 21 species, whereas 64 species have been recorded 
from a single eastern lake (Maxinkuckee in Indiana). Among animals 
inhabiting arid situations in California, the foothill chaparral areas, 
for example, there is a relatively large population as to species, each 
of which can be shown to have particular ecologic requirements. 
The point here involved is that in the eastern United States, where 
moisture in the atmosphere is continuously plentiful and where lakes 
and streams are present at all times of the year, the aquatic and 
related environments are finely divided ecologically, whereas in 
interior California (excluding the northwestern humid coast region), 
where the climate is relatively arid, where the atmosphere is low in 
relative content of water vapor, where lakes are few and the streams 
are of intermittent character, the aquatic and related environments 
show slight diversification. Incidentally, the ecologic niches in the 
arid territory are finely divided. 
It is of course true that the past geological history of a region con- 
trols to some extent the diversity of the aquatic fauna, but, even 
considering this complication, the meager amphibian (and fish) fauna 
of the west coast is undoubtedly conditioned to a very large degree 
by the arid nature of the region and the consequent slight diversi- 
fication of the aquatic environment. 
