Dear Sir—

I feel very much obliged to you for having sent me your new book, the results of which seem to inaugurate quite a new theory of irritability.¹ Besides I think your graphic method may be applied to the chick in the egg. I shall try in spring.²

What you say about the origin of certain instincts which probably must be ascribed to “modifications” or “variations” of the brain, not to experience and habit, was quite new to me and is to a certain degree proved to be true by Brown-Séquards experiments and Westphals observations, which shew that epileptiform-movements may not only be artificially produced in guinea-pigs but that the young of such individuals show the same abnormal phenomena without having been pricked. I remember not exactly when and where this important fact has been published.³ But it confirms not only your theory, it proves also that such instincts which are of no “service to the species” may be inherited. I wish you could find time to write on “the marvellous facts of instinct” as indicated in your ‘Variation of Animals and Plants under domestication’ 1868 vol. 1, p. 8.⁴ With many thanks I enclose the short notes from ‘Nature’⁵

I am dear Sir your’s most faithfully | W^m. Preyer