The Facts of Sex in Relation to Metabolism. 255 
theory maintained in “The Evolution of Sex” may be 
summed up in the following propositions :— 
In the individual life of a plant there is a marked contrast 
between the growing vegetative phase and the flowering 
reproductive phase. During growth anabolism is “relatively 
preponderant,” during the reproductive period katabolism is 
“relatively preponderant.” In animals also, reproduction 
usually occurs at the limit of growth, when anabolism begins 
to become less preponderant. 
All living creatures may be contrasted in terms of their 
relative activity, as measured by the rate and amount of 
movement and work which they accomplish, and by the rate 
and amount of potential energy stored. Thus one may con- 
trast plants and animals, gregarines and infusorians, hydroid 
and medusoid, reptile and bird, and so on throughout a long 
series of antitheses between relatively passive and relatively 
active forms. 
Parallel to this is the contrast between the sexes. 
Whether one considers the relative sizes of the sexes, or 
their essential reproductive functions, or the reproductive 
elements which they produce, or the secondary sexual 
characters, or what is known of their chemical constitution, 
or the factors which tend to produce male or female offspring, 
or the first hints of sexual differentiation among the simplest 
creatures, it seems to the authors of “The Evolution of Sex” 
that the female is the outcome and expression of relatively 
preponderant anabolism and the male of relatively prepon- 
derant katabolism. 
Thus the contrast between the sexes is brought into 
parallelism with the general contrast between relatively 
active and relatively passive, more katabolic and more 
anabolic organisms, and is regarded as one expression of the 
alternatives of protoplasmic metabolism which Bo be read 
throughout the whole organic world. 
While in the main accepting, or continuing to accept, the 
general interpretation suggested in “The Evolution of Sex,” 
it seems to us necessaay to correct an inaccuracy in the state- 
ment of the principal theorem—an inaccuracy which has given 
rise to misunderstandings on the part of more hostile critics. 
We seek to restate the theorem in more precise terms. 
