we find in the anthropoid apes." (G. Elliot Smith, in _Descriptive and Illustrated Catalogue of the Physiological Series of Comparative Anatomy Contained in the Museum of the Royal College of Surgeons of England_, second edition, vol. ii.) A full statement of Elliot Smith's investigations, with diagrams, is given by Bullen, _Journal of Mental Science_, July, 1899. It may be added that the whole subject of the olfactory centres has been thoroughly studied by Elliot Smith, as well as by Edinger, Mayer, and C.L. Herrick. In the _Journal of Comparative Neurology_, edited by the last named, numerous discussions and summaries bearing on the subject will be found from 1896 onward. Regarding the primitive sense-organs of smell in the various invertebrate groups some information will be found in A.B. Griffiths's _Physiology of the Invertebrata_, Chapter XI. The predominance of the olfactory area in the nervous system of the vertebrates generally has inevitably involved intimate psychic associations between olfactory stimuli and the sexual impulse. For most mammals not only are all sexual associations mainly olfactory, but the impressions received by this sense suffice to dominate all others. An animal not only receives adequate sexual excitement from olfactory stimuli, but those stimuli often suffice to counterbalance all the evidence of the other senses. We may observe this very well in the case of the dog. Thus, a young dog, well known to me, who had never had connection with a bitch, but was always in the society of its father, once met the latter directly after the elder dog had been with a bitch. He immediately endeavored to behave toward the elder dog, in spite of angry repulses, exactly as a dog behaves toward a bitch in heat. The messages received by the sense of smell were sufficiently urgent not only to set the sexual mechanism in action, but to overcome the experiences of a lifetime. There is an interesting chapter on the sense of smell in the mental life of the dog in Giessler's _Psychologie des Geruches_, 1894, Chapter XI, Passy (in the appendix to his memoir on olfaction, _L'Année Psychologique_, 1895) gives the result of some interesting experiments as to the effects of perfume on dogs; civet and castoreum were found to have the most powerfully exciting effect.