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senting them. If there be several maxima suited for 
nearly the same province, the maximum of greatest intensity 
will choke out the others. So, too, there are probably 
many maxima now unoccupied, as for instance, the thistle 
represented a maximum of vegetable life in South America, 
but till man imported the thistle to fill it up, other maxima 
of less intensity held the ground. In some cases possibly 
several maxima are closely related, and differ little in their 
intensity, so that slightly differing species exist together, 
and may in their variation pass one into the other, as 
perhaps in brambles and some species of St. J ohn’s wort, &c. 
If then the province of a species, i. e. the physical geo- 
graphy of a country alter, and its enemies and food with 
them, clearly the maximum will shift and the species change. 
But this is not the evolution of new species, though to a 
person who only notes geological evidence it appears so. For 
just as in a storm the lightning shews the trees still, though 
really waving to and fro, so the different species in geology 
are probably but steps in a constant change. Such a change 
of course must be slow for life to follow it, for a species con- 
sists quite as much in a bundle of acquired and transmitted 
habits as in a certain formation of organs, and the change in 
habit will probably be far slower than the change in form. 
How then do new species arise ? For we see that, if the 
species be a maximum of vitality, in a multitudinous progeny 
those nearest the type will choke out the others and the 
species will be stable. Varieties will be connected with 
maxima of vitality in two ways. Firstly, slight differences 
in the province will slightly shift the maximum. Thus 
mountain sheep would be more agile than low land sheep. 
Secondly, in such a way as this. Suppose this table 
a low mound, narrow though long. Then the height at any 
point will be a function of the distances from the N. and E. 
walls of the room. There will be one point of maximum 
height, but whilst a change N. or S. produces a great change 
in the altitude, one E. or W. will produce but little. So 
