Sir,--I am surprised that so accurate a man as my friend Mr. H. G. Atkinson should have so misunderstood my meaning as to say that I "deny to the lower animals their instincts," and "strive to make facts square with my theories,"--and further that my "denial of the existence of such powers is as futile as it is in utter defiance of fact." Now will it be believed that I have never denied the existence of instinct; I have, it is true, denied that it has been proved that birds build their nests by instinct, and have maintained that a consideration of all the facts is, in this case, entirely opposed to that view; and I suppose Mr. Atkinson himself would admit that each case of supposed instinct is to be judged by itself, according to the facts of that case. I have also expressed my belief that much of the supposed instinct of the lower animals can be explained by initiation and observation, and the peculiar organisation which necessitates certain movements, and renders certain actions pleasurable. In my short essay on "Instinct in Men and Animals," published in my "Contributions to the Theory of Natural Selection," I maintain that the senses and mental powers of the lower animals are probably so different from ours, and are so little known, that we cannot safely arrive at conclusions drawn from a comparison of their actions with ours; but that among the higher animals, where there is a closer resemblance in senses and mental powers to ourselves, the facts which I throughout appeal to, do not prove instinct. I maintain that experiments on instinct have not been sufficiently carried on, and I conclude, not that there is no such thing as instinct, but that it should not be accepted as proved in any particular case "until all other possible modes of explanation have been exhausted." Having thus expressed myself, I do not like being accused of the positive and dogmatic denials of instinct, which Mr. Atkinson imputes to me. I am open to conviction by facts, and I may remark that at the British Association meeting at Brighton, a valuable paper was read by Mr. Spalding relating a series of experiments on newly-hatched chickens, which go to show that many simple actions, involving appreciation of form and distance, are well performed without experience; but we have as yet no experiments to show that the exceedingly complex actions involved in the higher instincts can be so performed.