1889] Recent Literature. 59 
rates of flight in the various species; and (2) a systematic portion in 
which the five hundred and sixty species of birds known to occur in the 
Mississippi Valley are treated serially, the movements of each during the 
seasons of 1884 and 1885 being traced with as much exactness as the 
records furnished by the one hundred and seventy observers in the dis- 
trict permit.” 
The labor of elaborating and compiling this report has evidently been 
very great, not only the data from this large number of field observers 
having been collated, but much matter relating to distribution having 
been incorporated from published sources. Part IJ thus contains a very 
large amount of information bearing upon the migrations and breed- 
ing ranges of the birds found in the Mississippi Valley. 
Under the head of ‘Theoretical Considerations’ (pp. 11, 12), the author 
states his belief that the autumnal migration is ‘‘the result of two causes— 
the approach of winter and the failure of the food supply,” and that the 
spring migration is due to ‘‘a strong home love—an overpowering desire 
to be once more among the familiar scenes of the previous summer.” In 
respect to the autumnal migration, it is considered obvious that the fail- 
ure of the food supply is the primary cause of the movement, ‘‘since it is 
well known that single individuals of species which retire far to the south 
often remain behind, and, favored by an abundance of food, withstand the 
most severe weather.” The impulse that leads to the return of birds in 
spring to their summer homes is doubtless not to be wholly accounted for 
by what has been called ‘‘love of home,” to which theory the editor in a foot- 
note (p. 11) takes strong exception. He attributes this movement to fail- 
ure of ‘‘the food supply,” to unfavorable ‘‘climatic conditions,” ‘‘to physio- 
logical restlessness” induced by ‘‘the approach of the breeding season,’ 
and to an inherited ‘‘irresistible impulse to move at this particular time of 
the year.” Thereasons given for the autumnal movement clearly afford a 
satisfactory explanation, since in most instances were migratory species to 
remain in winter at their accustomed breeding grounds few would escape 
total extinction. The reasons for the return movement are more complex 
and less obvious. Lack of food can hardly be assumed as one of them. 
Increase of temperature at their winter quarters, as spring advances, must 
render the lower latitudes at this season uncongenial, and at the same 
time awaken the periodic activity of the reproductive system, which 
‘‘sives rise to physiological restlessness,” and imparts ‘‘the irresistible 
impulse to move at this particular season of the year” toward the breed- 
ing habitat of the species. While it is assumed that birds are directed 
thither by the ‘‘unerring instinct” of ‘‘inherited memory,” the ultimate 
choice of a particular district by the different individuals may be deter- 
mined by a true home love, which beyond question leads birds to the 
same fields and nesting trees for many successive years, and possibly also 
their descendents for generations. 
If, however, we may reason from birds to migratory fishes, whose migra- 
tions are quite as exact and methodical as those of birds, it would seem 
that there is still something to explain in regard to the return of birds 
