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Jan 30 /55/ On theory of Descent, a divergence is implied & I think diversity of structures supporting more life is thus modified. Now in considering amount of life supported in given area, besides size as an element, as in Trees & Elephant, besides period of non-active during winter in cold climate, I think some such element as amount of chemical change shd if possible be taken as measure of life, viz amount of carbonic acid expired or oxygen in plants. I have been led to this by looking at a heath thickly clothed by heather, & a fertile meadow, both crowded, yet one cannot doubt more life supported in second than in first; & hence (in part) more animals are supported. This is first cause, but more results from struggle, (I must think out the last propositions).

Heath, Pinewoods, Lakes, Arctic Regions many individuals few species. It follows that if there

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(18) Always remember how organisms are most importantly related to other organisms

be few species there may be many individuals, as compared to the individuals species, when many exist, in an equal area. So we have to account for few species, where not much means to support life, which perhaps is almost self-evident.

The number of species depends on number goes on increasing in geometrical ratio - because relations get more & more complicated.

(The most important comparison wd be an area of very fertile uniform land & an area of very sterile land; which wd support in proportion to number of species, the most diverse forms.)?

[in margin:] In Polar region they have to fight against only extreme cold & not complex relations. So on mountains.