The work is a very able combination of two different aims. On the one hand it affords the technical student the outline of a wholly new and distinctive manual of human embryology (up to a certain extent) and general anatomy; and this is intimately bound up by his method with a kind of historical introduction to general anthropology. At the same time the book forms a second part of the _History of Creation_. It builds up the most important chapter of the later work, from the philosophical point of view, namely, that which deals with the origin of man, into a fresh volume; and it represents the first popular treatment of embryology on broad philosophic lines—a thing that had never been attempted before. Springing up from this double root, the work is certainly one of the most successful things in the whole of Haeckel’s literary career. Moreover, it is not merely a compendium of a larger work, like the _History of Creation_. In spirit and form it is an original work, and gives his very best to the reader. As far as its general effect is concerned, the double-address of the work has had its disadvantages. The academic students who were hostile to it have once more selected for attack certain excrescences and gaps that were merely due to the exigencies of popular treatment. On the other hand, the general reader found it, in spite of the popular form, on which Herculean labour had been spent—one has only to think of the details of embryology—a book that was not to be “read” in the ordinary sense of the word, but studied. The first edition appeared in 1874. A fifth edition has now been published, equipped with the finest illustrations, both from the artistic and the scientific point of view, that have ever appeared in a popular work on embryology. We find in the _Anthropogeny_ all that the nineteenth century has learned or surmised with regard to the ancestral history of mankind. Even the gastræa-theory—the gastræa belonging to man’s direct ancestry—is dealt with in popular fashion as far as this was possible.