A 
280 Proceedings of the Royal Physical Society. 
10. ConcLustons.—(a) Many biologists will, we believe, 
accept the following propositions as statements of facts, 
which must be distinguished, of course, from such inferences 
as we or others may draw from them :— 
That organisms may be arranged in series of contrasted 
greater or less activity—activity being measured by the 
amount of movement, or, in more general terms, by the rate 
of transformation of potential into kinetic energy. 
That the sexes are examples of this general contrast, 
the males being the more active, the females the more 
passive; that the reproductive elements produced by the 
two sexes are In a similar manner contrasted, the sperms 
being much more active than the ova; and that the incipient 
sexual dimorphism of unicellular organisms is also parallel. 
That associated with this difference of physiological 
habit are differences of (a) size, (b) form, and (c) chemical 
composition ; the female being generally larger, less adapted 
for movement, and with a relatively greater store of reserve 
material. 
That the sex of the adult may, in some cases, be 
determined by the nutrition of the embryo, more abundant 
nutrition favouring the production of females rather than of 
males. 
(b) What we have sought to emphasise is that in contrast- 
ing the sexes and their reproductive elements (and all active 
and passive organisms), attention must, as precisely as 
possible, be expressed in contrasted ratios. The storage of 
potential energy in a female need not be absolutely greater 
than in the corresponding male (though in some cases, ¢9., 
the cochineal insects it is so); our contention is that in the 
: fin op A 
female the ratio K 18 greater than the corresponding vital 
ratio in the male. In the great majority of cases of the 
food assimilated and stored by a male organism the greater 
amount is used, after growth has ceased, for movement and 
for maintaining the general functions of the body, the repro- 
ductive function making relatively small demands on the 
nutritive store; while in the female organism a relatively 
