The line of demarkation between instinct and reason is a mezzotint, reason being often instinctive, and instinct being as frequently flavoured with judgment, ‘Instinct is usually regarded as a special property of the lower animals, and contrasted with the conscious reason of man. But just as reason may be looked upon as a higher form of the understanding or intellect, and not as something essentially distinct from them, so a closer examination shows that instinct and the conscious understanding do not stand in absolute contrast, but rather in a complex relation, and cannot be sharply marked off from each other.’ It is instinct that urges the bird to build its nest; but when birds whose habit it is to build on the ground learn, on the introduction of cats into the neighbourhood, to change their nesting-places to the tree-tops, intelligence and thought are necessary. The first time Cavy (one of my guinea-pigs) smelled a cat, she was almost scared to death. She jumped back from it as if she had come in contact with a red-hot stove, and screamed and kept on screaming, and shot down under my coat as if she were about to be crucified. After a little while I tried to pull her out, but she refused, and kept hiding. The second time the kitten was presented to her the result was the same. But after two or three days of association, she paid little more attention to it than to the other guinea-pigs. She had never seen a cat before. _It was the odour of the carnivore_ that terrified her, and the effect was purely instinctive. But instinct was soon modified by intelligent experience. (_Poor dear little Cavy! I wonder where she is now!_) Both instinct and reason (and one, too, just as much as the other) are absolutely dependent upon processes that are purely mechanical—that is, upon brain processes; and brain processes depend upon brain structure, which is inherited. Hence, reason is, in a certain sense, as truly inherited as instinct is. A being must be born with the particular nervous apparatus by means of which reasoning is carried on, or with the power or disposition to develop this apparatus, or he will never reason. The genius of the partridge in cajoling the passer-by from her nest is called instinct, but it is not more inherited than was the genius of Shakspere. Experience simply calls into being that, whatever it is in each particular being, which is inherited. Sir Isaac Newton took to philosophy and Ole Bull to music not less inevitably than the duck takes to water or the hound to hunting. Reason is, hence, inherited by every man, who has it as truly as his erect posture and plantigrade feet. There is something in the past of all of us and of everything which has determined, and which may be used to account for, everything that to-day exists or happens, even to the style and behaviour of every leaf that flutters in the forest, and to the eccentricities of our opinions and handwritings.