The whole subject of comparative psychology had a special and peculiar fascination for Mr. Romanes, partly on account of its intimate connection with the theory of evolution, and partly from its bearing on those deeper philosophic problems which were never long absent from his thoughts. His treatment of the phenomena of instinct in 'Mental Evolution in Animals,' and elsewhere, was both comprehensive and exact, and still forms, in the opinion of competent authorities, the best general account of the subject that we have; though, had he lived to review and consolidate his work, some changes would probably have been introduced in view of later discussions on the nature and method of hereditary transmission. His arguments in 'Mental Evolution in Man,' in support of the essential similarity of the reasoning processes in the higher animals and in man, created a stir, at the time of their publication, which was in itself evidence that his critics felt that they had a writer and thinker that must be seriously and sharply met. He hoped by this work to win over the psychologists to the evolution camp; and he himself felt strongly that in some cases, when he failed fully to convince them of the adequacy of his method of treatment and of the arguments he adduced, it was rather in matters of definition than in matters of fact that the source of their differences lay. He was somewhat disappointed that his terms 'recept' and 'receptual' for mental products intermediate between the 'percept' and the 'concept' were not more generally accepted by psychologists, since, in his matured opinion, they and the conception they represent were eminently helpful in bridging the debatable space between the intellectual powers of man and the faculties of the lower animals. It was Mr. Romanes' intention to continue the mental evolution series and to deal, in further instalments of his work, with the intellectual emotions, volition, morals, and religion. This intention, however, he did not live to fulfil. His further development of mental evolution in the light of his later conclusions in the region of philosophical and religious thought would have been profoundly interesting. But one's regret that this part of his life work remained incomplete is tempered by the recollection that what he did complete was so worthily done. For, in the words of Mr. Lloyd Morgan, which were quoted with approval by Dr. Burdon Sanderson in his Royal Society obituary notice: 'by his patient collection of data; by his careful discussion of these data in the light of principles clearly and definitely formulated; by his wide and forcible advocacy of his views; and, above all, by his own observations and experiments, Mr. Romanes left a mark in this field of investigation and interpretation which is not likely to be effaced.'