A DIFFERENCE IN THE METABOLISM OF THE SEXES 35
It is certainly no mere chance, but agrees with other well-known facts, that for the generation of the female organ more favorable external circum- stances must prevail, while the male organ may develop under very much more unfavorable conditions. 1
These facts are not conclusive, but they all point in the same direction, and are probably sufficient to establish a connection between food conditions and the determination of sex. But behind the mere fact that a different attitude toward food deter- mines difference of sex, lies the more fundamental, indeed, the real explanation of the fact, and this chemists and physiologists are not at present able to give us. Researches must be carried further on the effect of temperature, light, and water on varia- tion before we may hope to reach a positive conclusion. We can only assume that the chemical constitution of the organism at a given moment conditions the sex of the offspring, and is itself conditioned by various factors light, heat, water, elec- tricity, etc. and that food is one of these variables. 2 It is sufficient for our present purpose that sex is a constitutional matter, indirectly dependent upon food conditions, that the female is the result of a surplus of nutrition, and that the rela- tion reported among the lower forms persists in the human species.
In close connection with the foregoing we have the fact
1 G. KLEBS, Ueber das Verhdltniss des mdnnlichen und iveiblichen Geschlechts in der Natur, 1894, p. 19.
a Food affords the basis for metabolic changes in the parent organism, but it is probable that food is less directly related than heat and light to the determination of sex. Sachs, whose experiments must be given the greatest possible weight, has deter- mined that the ultra-violet rays of light are necessary to the chemical changes essen- tial to the formation of the reproductive organs. (J. SACHS, " Ueber die Wirkung der ultravioletten Strahlen auf die Bliithenbildung," Gesammelte Abhandlungen iiber Pflanten-Physiologie, Vol. I, pp. 293 seq.) More recently, Klebs has shown that by diminishing the intensity of light the development of female sex organs in ferns can be interrupted, so that in spite of the presence of male organs fertilization is impossible ; at the same time the prothallia are enabled in weak light to grow feebly and to put out small asexual processes, u 1m h in the presence of bright light become normal pro- thallia. Similarly, the development of sexual organs in algtt is dependent on a cer- tain intensity of light, and the plant remains sterile if the light is <liinim>hed below a certain poii, . i.EBS, Uebtr einige Probleme der PhysMogie der Fortf/lantutte,
1895, pp. I.}
