Phillips. — On a Connnon Vital Force. 613 



then' their progeny would increase and multiply until the 

 whole nation might become like them, when suddenly a 

 disease specially fatal to that one organization would appear 

 and extirpate it completely. But, as the rule of the vital 

 force is that no two things can be alike, it is at once seen 

 that no destruction of any one species can take place by any 

 one disease or ailment. 



This being granted, it follows that the power of divergence 

 of all living things is without limit. In China, with 400,000,000 

 of inhabitants, we have consequently the power to diverge or 

 naturally select 400,000,000 times. Similarly, in fowls, we 

 have as yet but entered upon their variations. There may be, 

 and doubtless are, thousands of other varieties yet to be 

 selected, which can each be made pure. And these varieties 

 fit themselves to climatic conditions as the conditions arise. 

 We have seen fowls upon this planet produced step by step, 

 variety after variety. But, nevertheless, no one can say that 

 there may not be a thousand varieties yet to be produced by 

 careful and judicious breeding or selection, suitable to a much 

 larger planet and somewhat different climatic conditions. For 

 the differences in fauna upon this planet, even during geo- 

 logical records, have been very remarkable. The vast differ- 

 ence between the moa and our domestic fowl opens up so 

 wide a field of divergence that the mind is lost in conjecturing 

 what the varieties may be of this one species alone of living 

 things. There may, indeed, be millions of types of fowls to 

 fill the gap between the moa and our common domestic hen. 



In sheep the power of divergence is very remarkable also. 

 A fellow-settler and I have been breeding Eomney Marsh 

 sheep for many years past. We both started with a certain 

 strain of blood which we called the " Colonel " blood, from the 

 name of the particular sheep imported. Our ewes also came 

 from the late Mr. Ludlam's breeding, of theHutt. Our residences 

 are only thirty miles apart ; but in fifteen years our sheep are 

 totally different in type. Now, what had we done ? We had 

 each followed out in our mind's-eye, and kept to besides, the 

 one particular variety or style of animal. The same with the 

 differences in black-faced sheep, which no doubt came from 

 the original black sheep. The same w^th the Lincolns, or 

 Leicesters, or any of the English breeds. So limitless is the 

 power of divergence that not only may each county in Eng- 

 land have its particular breed of sheep, but each parish, each 

 farm — that is, of course, so long as each variety can be kept 

 apart from the other, and distinct. Eix upon the type of sheep 

 you want, then breed in and select, is the plan. Yet, with 

 this vast field of difference before us, Darwin tries to show 

 that Mivart is wrong when he says that species change 

 through an internal force or tendency. The term "progressive 



