18 
mediate would be killed out, and thus two distinct species 
would arise, which might in course of time by further 
variation separate still further apart. 
Doubtless, however, this bifurcation goes back to very 
remote times. Carnivores and herbivores probably separated 
not as mammals but as reptiles, or even long before, whilst 
ruminants and non-ruminants may have separated since 
they became mammals. 
Thus Australia seems to have possessed at one time only 
some marsupial, which has bifurcated into various mar- 
supials, but not into any of another kind. The older the 
species grow the deeper is the gulf between them, and, like a 
river, we have to ascend nearly to the source before we can 
make a passage from one bank to the other. 
/ 
To recapitulate. — Maxima of vitality are species. Any 
alteration from the normal type produces less vitality, hence 
the normal type is stable. A slow change of physical 
geography, &c., slowly changes these maxima, and the 
species change with them, extinct species being generally 
glimpses of steps in this change. New species will generally 
arise from the bifurcation of maxima under circumstances 
over which man can exercise little control, and which, if he 
could, he would very likely alter so as either hardly to 
affect the maximum at all, or too rapidly for the species to 
shift with it. Selected breeding produces types of less 
vitality, and therefore will hardly produce new species. 
Thus the present stability of species is no argument against 
the doctrine of evolution. 
We hope we have not trespassed on the time of the 
Society in thus putting before them not new views, but 
perhaps a slightly new aspect of old views. Still as we felt 
a difficulty and thought we saw a solution, we felt we 
might ask their opinion upon it. 
