The regard in which he was held by his friends was such that he was sometimes appealed to by both parties in a dispute.  He was a man to be trusted with the confidence of his friends.] “Yes, you are quite right about ‘loyal,’” [he writes to Mr. Knowles], “I love my friends and hate my enemies—­which may not be in accordance with the Gospel, but I have found it a good wearing creed for honest men.” [But he only regarded as “enemies” those whom he found to be double-dealers, shufflers, insincere, untrustworthy; a fair opponent he respected, and he could agree to differ with a friend without altering his friendship.

A lifelong impression of him was thus summed up by Dr. A.R.  Wallace:—­

I find that he was my junior by two years, yet he has always seemed to me to be the older, mainly no doubt, because from the very first time I saw him (now more than forty years ago), I recognised his vast superiority in ability, in knowledge, and in all those qualities that enable a man to take a foremost place in the world.  I owe him thanks for much kindness and for assistance always cordially given, and although we had many differences of opinion, I never received from him a harsh or unkind word.

To those who could only judge him from his controversial literature, or from a formal business meeting, he often appeared hard and unsympathetic, but never to those who saw beneath the surface.  In personal intercourse, if he disliked a man—­and a strong individuality has strong likes and dislikes—­he would merely veil his feelings under a superabundant politeness of the chilliest kind; but to any one admitted to his friendship he was sympathy itself.  And thus, although I have heard him say that his friends, in the fullest sense of the word, could be reckoned on the fingers of one hand, the impression he made upon all who came within the circle of his friendship was such that quite a number felt themselves to possess his intimacy, and one wrote, after his death:  “His many private friends are almost tempted to forget the public loss, in thinking of the qualities which so endeared him to them all.”

Both the speculative and the practical sides of his intellect were strongly developed.  On the one hand, he had an intense love of knowledge, the desire to attain true knowledge of facts, and to organise them in their true relations.  His contributions to pure science never fail to illustrate both these tendencies.  His earlier researches brought to light new facts in animal life, and new ideas as to the affinities of the creatures he studied; his later investigations were coloured by Darwin’s views, and in return contributed no little direct evidence in favour of evolution.  But while the progress of the evolution theory in England owed more to his clear and unwearied exposition than to any other cause, while from the first he had indicated the points, such as the causes of sterility and variation, which must be cleared up by further investigation in order to complete the Darwinian theory, he did not add another to the many speculations since put forward.