Unicellular animals (Protozoa) I Cœlenterata, or Zoophytes. Animals without body-cavity, blood, or anus. _a._ Gastræads Gastremaria Cyemaria _b._ Sponges Protospongiæ Metaspongiæ _c._ Cnidaria (stinging animals) Hydrozoa Polyps Medusæ _d._ Platodes (flat-worms) Platodaria Turbullaria Trematoda Cestoda II Cœlomaria or Bilaterals. Animals with body-cavity and anus, and generally blood. _a._ Vermalia (worm-like) Rotatoria Strongylaria Prosopygia Frontonia _b._ Molluscs Cochlides Conchades Teuthodes _c._ Articulates Annelida Crustacea Tracheata _d._ Echinoderms Monorchonia Pentorchonia _e._ Tunicates Copelata Ascidiæ Thalidiæ _f._ Vertebrates I. Acrania-Lancelet (without skull) II. Craniota (with skull) _a._ Cyclostomes (“round-mouthed”) _b._ Fishes Selachii Ganoids Teleosts Dipneusts _c._ Amphibia _d._ Reptiles _e._ Birds _f._ Mammal Monotremes Marsupials Placentals: Rodents Edentates Ungulates Cetacea Sirenia Insectivora Cheiroptera Carnassia Primates (This classification is given for the purpose of explaining Haeckel’s use of terms in this volume. The general reader should bear in mind that it differs very considerably from more recent schemes of classification. He should compare the scheme framed by Professor E. Ray Lankester.) THE EVOLUTION OF MAN Chapter I. THE FUNDAMENTAL LAW OF ORGANIC EVOLUTION The field of natural phenomena into which I would introduce my readers in the following chapters has a quite peculiar place in the broad realm of scientific inquiry. There is no object of investigation that touches man more closely, and the knowledge of which should be more acceptable to him, than his own frame. But among all the various branches of the natural history of mankind, or _anthropology,_ the story of his development by natural means must excite the most lively interest. It gives us the key of the great world-riddles at which the human mind has been working for thousands of years. The problem of the nature of man, or the question of man’s place in nature, and the cognate inquiries as to the past, the earliest history, the present situation, and the future of humanity—all these most important questions are directly and intimately connected with that branch of study which we call the science of the evolution of man, or, in one word, “Anthropogeny” (the genesis of man). Yet it is an astonishing fact that the science of the evolution of man does not even yet form part of the scheme of general education. In fact, educated people even in our day are for the most part quite ignorant of the important truths and remarkable phenomena which anthropogeny teaches us.