CO 
ZOOLOGICAL LITERATURE. 
or allied species in tlie Eastern. Again^ specimens from the 
Pacific coast arc apt to be darker in colour than those from the 
interior. Pirds of any two representative species from the 
frontiers of their respective ranges present a combination of 
characters explicable only on the supposition of hybridity. 
Notable instances of this are found in the genera ColapteSj Cya^ 
nura, Junco, and Helminthophaga. — Prof. Paird then proceeds 
to treat of the eastward movement of American birds^ and its 
influence on the ornis of Greenland and Europe^ and vice versa, 
European land-birds reach Greenland by way of Iceland and 
the Eieroesj those found on the continent of North America 
reach it by autumnal movement from Greenland in company 
with strictly North American species. Most American birds 
which reach Europe have occurred in England, which they 
make, not by way of Iceland, but by direct voyage, aided by the 
winds. The migrations of birds are generally more or less in a 
north and south direction, influenced materially by rivers, moun- 
tains, forests, and the like. While in spring they usually proceed 
to the very spot of their birth by a direct line, their return in 
autumn is often by a different route. The vernal movement, 
too, is performed much more rapidly and with fewer halts by 
the way than the autumnal. The nature of the migratory im- 
pulse is not discussed. — It must be observed that the results 
which we have here set down as arrived at by the author are 
reached only after a close examination of the very large and 
carefully collected series of specimens in the Smithsonian Insti- 
tution and the collation of numerous recorded facts. Many 
comparative lists of species throwing light on the subject are 
also introduced. Some extracts from this paper are given in 
Ann. & Mag. N. II. 1866, xviii. pp. 141-144; and the whole is 
reprinted, ^Ibis,' 1867, pp. 257-293; while a German translation 
is contained ^ Journ. fur Orn.^ 1866, pp. 244-269, 338-352. 
CouEs, Elliott. From Arizona to the Pacific. Ibis, 1866, 
pp. 259-275. 
, Fort Whipple in Arizona possesses much in common with the 
coast of Southern California, though the two are in many points 
strikingly contrasted. The author had a fine opportunity of 
comparing the ornis of these districts in passing from one to the 
other, a distance of 500 miles. Hardly any change was noticed 
until the Colorado was nearly reached; here the author had the 
opportunity of determining many of the water-birds found in 
the district. Further westward lies the Colorado Desert, where 
hardly a bird was seen until the ^^sink^^ of the Mojave was 
attained, which seems to be a meeting-point of several eastern 
and western species. Beyond this lie the San Bernardino 
Mountains, whence to the coast the country is an open and flat 
plain, the resort of a very distinct set of birds. The paper. 
