His son George was Second Wrangler in 1868; as a boy he was an enthusiast in heraldry.) has been a wonderful pleasure to us.

George has not slaved himself, which makes his success the more satisfactory.

Farewell, my dear Huxley, and do not kill yourself with work.
(209/1.

The following group of letters deals with the problem of the causes of the sterility of hybrids.

Mr.Darwin's final view is given in the "Origin," sixth edition (page 384, edition 1900).