[135]

[To Watson's point no. 3:] I see this is common opinion & was mine but I have come to doubt. To my mind at the time, the cause of divergence was an important step

[To Watson's point no. 4:] I do not see why variations should not fluctuate backwards & forwards, without much Divergence.

[136]

[page 2 of letter from Watson]

[To Watson's point no. 8:] I think I can show that this is not so.—

[137]

[Page 3 of letter from Watson]

C. of Good Hope. / Species which are rare & all wd become rare if infinitely many species / will be very liable to extermination. Moreover I fully believe (Back of Paper)

137v]

that rare species (from fewness of individuals & therefore less chance of profitable variations) will vary less quickly, (possibly close interbreeding would come into play with very rare species: mem decrease in size in Auroch Red Deer &c.) so that the great increase of number of species would act as a sort of regulator to further increase. Numerous Physical conditions are not infinitely different in kind, & as far as adaptation to physical conditions are concerned the number of species would soon come to a limit. But I fully, most fully admit, that the organic relation will tend, will increase if number of species, to go on getting more & more complex, & thus there will be tendency to increase in number of new species.

This will come in check above alluded to.

We do not know that full number anywhere arrived at.— Mem. naturalised plants at C. of Good Hope.— Also dominant invading species will destroy many representative species: Mem. Hooker on Australia.—

[138]

[Page 4 of letter from Watson]

Ch 6

I daresay this has taken place to small extent; it is when "adaptive" characters affect closely related forms