920 
Proceedings of the Royal Society 
then, a continued surplus of anabolism over katabolism, — the 
result is necessarily a growth in size, a reduction of kinetic energy 
and movement, an increase in potential energy and reserve food- 
material. Irregularities thus tend to disappear; surface-tension, 
too, may aid, and the cell acquires a spheroidal form. The result — 
a large and quiescent ovum — is thus intelligible enough. Again, 
starting from the amoeboid cell, if katabolism be in growing pre- 
ponderance, the increasing liberation of kinetic energy thus implied 
must find its outward expression in increased activity of movement 
and in diminished size ; the more active cell becomes modified in form 
by passage through its fluid environment, and the natural result is the 
flagellate sperm-cell. The morphological characters of the sexual ele- 
ments are thus expressible as the results of preponderant anabolism 
Fig. 3. 
in the female and katabolism in the male. It would lead us too far 
at present from our direct argument to show how this applies to the 
Protozoa, which exhibit a practical coincidence of cell and organism, 
and which should be defined not so much as 11 organisms devoid 
of sexual reproduction,” but rather as “ undifferentiated reproductive 
cells (protosperms or protova, as they may in fact be called) which 
have not built round themselves a body.” Not only do the Protozoa 
illustrate, in the great lines of their differentiation, and in the phases 
of their life-histories, the outcome of preponderant or equated ana- 
bolism and katabolism ; but in the incipient dimorphism of two 
conjugating individuals or the macro- and microspores of higher 
