Mr. Ellis is to be congratulated on the difficult task which he has successfully accomplished in this book, of collecting the enormous material scattered in books and periodicals concerning the differential characteristics of man and woman, sifting it, and presenting it to his readers in an agreeable and methodical manner. He steers remarkably clear of the marked bias which has vitiated in the past the conclusions of various writers on this fascinating subject, and a great feature of the work is, therefore, the calm judicial way in which evidence is presented and the scientific spirit which pervades it.