254 Proceedings of the Royal Physical Society. 
growth is an example of a familiar syllogistic fallacy. For 
from the premises (a) that the rate of growth decreases with 
time, and (0) that the ratio of protoplasm to nucleoplasm 
increases with time, the inference that protoplasm retards 
growth is obviously illegitimate. 
5. Facts oF SEX AND SEXUAL RepPRoDUcTION.—In illus- 
tration of what we mean by the facts of sex and sexual 
reproduction, we may recall the following, some of which, 
be it carefully noticed, are only “average truths,” to which 
it is easy to find individual exceptions. 
(a) In cases of incipient sexual dimorphism, which occur 
among Protozoa and Protophyta (eg., Vorticella and Volvozx), 
we have to distinguish a larger, apparently better nourished, 
more passive macrogamete from a microgamete with opposite 
characteristics. 
(6) Among Metazoa, in the majority of cases, reproduction 
occurs by the liberation of unicellular germs from dimorphic 
individuals or males and females. The female organisms 
tend to be more passive, larger, plainer, and of longer life; 
the male organisms tend to be more active, smaller, more 
decorative, and of shorter life. 
(c) Excepting a restricted minority of parthenogenetic 
organisms, the continuance of life seems to depend on the 
union of dimorphic sex-cells. The ova or reproductive cells 
produced by the female tend to be large, passive, rich in 
stores of potential energy; the sperms, or reproductive cells 
produced by the male, tend to be minute, active, and with 
little store of potential energy. These reproductive cells are 
mutually dependent, and in fertilisation they unite in an 
intimate and orderly manner. 
(d@) The quantity of reproductive material produced by 
the female is generally greater than that produced by the 
male, partly because the female supplies the germ with a 
capital of nutriment, and partly for other reasons. 
(e) In the development of ova, embryos, and larve, it 
seems that abundant nutrition and other conditions which 
favour the accumulation of matter and potential energy, tend 
to the production of female rather than male offspring. 
6. Tue THESIS oF “THE EvoLUTION or SEx.”—The general 
