to them as to most other animals, means an unwonted amount
of physical exercise besides the everyday runs for life from
their natural enemies, and an unusual amount of energy is used
up. If a doe dislikes the attention of a special buck, miles of
racing result. If jealous males meet, furious battles take place.
The strain on both sexes could not possibly be endured at any
other season of the year. With approach of cold weather, climatic
deprivations and winter dangers commence and rut closes. In all
wild animals, rut occurs only when the climatic and other
conditions favor the highest physical development. This law holds
good in all wild birds, for it is then only that they can stand
the strain incident to love-making. The common American crow is a
very good study. In the winter he travels around the ricefields
of the South, leading a tramp's existence in a country foreign to
him, and to which he goes only to escape the rigors of the
northern climate. For several weeks in the spring he goes about
the fields, gathering up the worms and grubs. After his long
flight from the South he experiences several weeks of an almost
ideal existence, his food is plentiful, he becomes strong and
hearty, and then he turns to thoughts of love. In the pairing
season he does more work than at any other time in the year:
fantastic dances, racing and chasing after the females, and
savage fights with rivals. He endures more than would be possible
in his ordinary physical state. Then come the care of the young
and the long flights for water and food during the drought of the
summer. After the molt, autumn finds him once more in flock, and
with the first frosts he is off again to the South. In the wild
state, rut is the capstone of perfect physical condition." (A.W.
Johnstone, "The Relation of Menstruation to the other
Reproductive Functions," _American Journal of Obstetrics_, vol.
xxxii, 1895.)

Wiltshire ("Lectures on the Comparative Physiology of
Menstruation," _British Medical Journal_, March, 1888) and
Westermarck (_History of Human Marriage_, Chapter II) enumerate
the pairing season of a number of different animals.

With regard to the breeding seasons of monkeys, little seems to
be positively known. Heape made special inquiries with reference
to the two species whose sexual life he investig