This is an OCR edition without illustrations or index. It may have numerous typos or missing text. However, purchasers can download a free scanned copy of the original rare book from GeneralBooksClub.com. You can also preview excerpts from the book there. Purchasers are also entitled to a free trial membership in the General Books Club where they can select from more than a million books without charge. Original Published by: Macmillan in 1869 in 474 pages; Subjects: Medical / Genetics; Psychology / General; Psychology / Cognitive Psychology; Science / Life Sciences / Evolution; Science / Life Sciences / Genetics & Genomics;