Mr. Romanes read widely and observed much, and no one less deserved the charge of writing without observing, or of being a 'paper philosopher.' Both these books abound in stories of animals, and are full of interest for anyone caring at all for 'beasts,' quite apart from the special object of the books. Lecturing and reviewing were, so to speak, pastimes to him, and gave him little trouble. One lecture given at the Royal Institution on 'The Mental Differences between Men and Women' drew upon the head of the unlucky lecturer a great storm of indignation--why, the writer of this memoir has never been able to discover. In May 1886, Mr. Romanes read a paper before the Linnean Society on 'Physiological Selection, an additional suggestion on the origin of species.' This paper was the outcome of many years' study of the philosophy of evolution, during which time he had gradually been coming to the conclusion that natural selection cannot be regarded as the sole guiding factor in the production of species, but that there must be some other cause at work in directing the course of evolution. The theory of natural selection rests on two classes of observable facts: first, that all plants and animals are engaged in a perpetual struggle for existence, there being in every generation of every species a great many more individuals born than can possibly survive; and secondly, that the offsprings, although closely resembling the parent form, do present individual variations. It follows, therefore, that those individuals presenting variation in any way beneficial to them in the struggle for existence will survive as being the fittest to do so, Nature, so to speak, selecting certain individuals of each generation, enabling them not only to live themselves, but also to transmit their favourable qualities to their offspring. If a special line of variation is in some way preserved, there may result a variety so fixed and so distinct from the parent and collateral related forms as to constitute a separate species. Further, since the environment (_i.e._ the sum total of the external conditions of life) is continually changing, it follows that natural selection may slowly alter a type in adaptation to the slowly changing environment, and if in any case the alterations effected are sufficient in amount to lead naturalists to name the result a distinct species, then natural selection has transmuted one specific type into another. Mr. Romanes pointed out that the theory of natural selection only accounts for such organic changes as are of _use_ to the species--by use signifying life-preserving--that it is, in fact, a theory of the origin and cumulative development of adaptations, whether these be distinctive of species, or of genera, families, classes, &c.