As to M. Ribot’s assertion, that to the heredity of modifications there are many exceptions, I readily agree with it, and can only say that it is exactly what I should expect; the lesson long since learnt by rote, and repeated in an infinite number of generations, would be repeated unintelligently, and with little or no difference, save from a rare accidental slip, the effect of which would be the culling out of the bungler who was guilty of it, or from the still rarer appearance of an individual of real genius; while the newer lesson would be repeated both with more hesitation and uncertainty, and with more intelligence; and this is well conveyed in M. Ribot’s next sentence, for he says—“It is only when variations have been firmly rooted; when having become organic, they constitute a second nature, which supplants the first; when, like instinct, they have assumed a mechanical character, that they can be transmitted.” How nearly M. Ribot comes to the opinion which I myself venture to propound will appear from the following further quotation. After dealing with somnambulism, and saying, that if somnambulism were permanent and innate, it would be impossible to distinguish it from instinct, he continues:— “Hence it is less difficult than is generally supposed, to conceive how intelligence may become instinct; we might even say that, leaving out of consideration the character of innateness, to which we will return, we have seen the metamorphosis take place. _There can then be no ground for making instinct a faculty apart_, _sui generis_, a phenomenon so mysterious, so strange, that usually no other explanation of it is offered but that of attributing it to the direct act of the Deity. This whole mistake is the result of a defective psychology which makes no account of the unconscious activity of the soul.” We are tempted to add—“and which also makes no account of the _bonâ fide_ character of the continued personality of successive generations.” “But we are so accustomed,” he continues, “to contrast the characters of instinct with those of intelligence—to say that instinct is innate, invariable, automatic, while intelligence is something acquired, variable, spontaneous—that it looks at first paradoxical to assert that instinct and intelligence are identical.