17 



there will be variations in some characteristics which will 

 produce little alteration in the whole vitality. Thus 

 amongst Vvdlcl oxen probably no varieties without horns 

 would exist, for they affect the vitality. Amongst pro- 

 tected races they do not, and so hornless varieties arise. 

 Still these varieties are but varieties, and are not steps 

 tow^ards a new maximum which a gulf of lesser vitality 

 still separates them from. 



Or let us consider the varieties that we try to make by 

 select breeding. These are least of all likely to produce 

 new species. We simply by main force depress vitality 

 in removing individuals as far as we can from the normal 

 type, and when the vitality is sufficiently depressed we can 

 go no further. As for altering the province, the inde- 

 pendent variables, so to speak, we know so little how to do 

 it, and certainty could not do it gradually enough, that we 

 have no chance in this way of effecting anything. 



How then can new species arise ? Apparently in some such 

 way as this, by what \ve may call the bifurcation of a 

 maximum. If we drew a horizontal line along which the 

 variation of the organs of an animal were expressed and the 

 corresponding vitality were drawn by ordinates, we should 

 get a curve we might call the vitality curve whose maxima 

 values would be species. As time elapses and the conditions 

 of the earth, &;c., altei*, the constants, so to speak, of the 

 curve alter, and we get our curve to vary and the maxima 

 shift ; and as the curve alters, one maximum may separate 

 into two or more others, and thus in the lapse of time one species 

 may separate into two or more others. Roughly to illustrate 

 it, suppose some species developed free from the influence 

 of carnivora,and that, owing to various causes, size little effects 

 its vitality, it may vary all through, from little and swift to 

 big and heavy. Nov/, introducing carnivora, we can see how 

 a bifurcation of our maximum would take place. The very 

 light and swift would preserve themselves by their agility, 

 the strorig and heavy by their strength, whilst the inter- 



