, Bd. III, Heft 5) has also argued in
favor of a chief sexual period in the year in man, with secondary
and even tertiary climaxes, in March, August, and December. He
finds that in some families, for several generations, birthdays
tend to fall in the same months, but his paper is, on the whole,
inconclusive.

Some years ago, Prof. J.B. Haycraft argued, on the basis of data
furnished by Scotland, that the conception-rate corresponds to
the temperature-curve (Haycraft, "Physiological Results of
Temperature Variation," _Transactions of the Royal Society of
Edinburgh_, vol. xxix, 1880). "Temperature," he concluded, "is
the main factor regulating the variations in the number of
conceptions which occur during the year. It increases their
number with its elevation, and this on an average of 0.5 per
cent, for an elevation of 1 deg. F." Whether or not this theory may
fit the facts as regards Scotland, it is certainly altogether
untenable when we take a broader view of the phenomena.

Recently Dr. Paul Gaedeken of Copenhagen has argued in a detailed
statistical study ("La Reaction de l'Organisme sous l'Influence
Physico-Chimiques des Agents Meteorologiques," _Archives
d'Anthropologie Criminelle_, Feb., 1909) that the
conception-rate, as well as the periodicity of suicide and allied
phenomena, is due to the action of the chemical rays on the
unpigmented skin in early spring, this action being
physiologically similar to that of alcohol. He seeks thus to
account for the marked and early occurrence of such periodic
phenomena in Greenland and other northern countries where there
is much chemical action (owing to the clear air) in early spring,
but little heat. This explanation would not cover an autumnal
climax, the existence of which Gaedeken denies.

In order to obtain a fairly typical conception-curve for Europe, and to
allow the variations of local habit and custom to some extent to
annihilate each other, I have summated the figures given by Mayr for about
a quarter of a million births in Germany, France, and Italy,[156]
obtaining a curve (Chart 2) of the conception-rate which may be said
roughly to be that of Europe generally. If we begin at September as the
lowest point, we find an autumn rise culminating in the lesser maximum of
Christmas, followed by a minor depression in January and February. Then
comes the