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, «fec., 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. 



