In this work he explained the descent of man fully from the before-named principles of the descent, evolution, and selection theories, of which we have given all the essentials in the foregoing presentation. He carefully enumerates everything in the structure of the human body that reminds us of our relationship with the animals--especially those embryonic phenomena and rudimentary organs in man which are still to be found in use and in a more developed state in different animal species, and which led him to imagine our ancestors now with a tail, then with sharp ears, now living in the water, then being hermaphrodites. He reviews the spiritual qualities of man, and finds for them all analogous qualities in the animal world. He finds in his work on {43} "Expression of the Emotions in Man and Animals," published in 1872, new confirmation of the genealogical relationship of both. He looks over the whole course of the zooelogical system and of palaeontological discoveries, and searches for the points where the branches and twigs of the animal pedigree of man must have diverged. To begin with the lowest branches, he thinks the most important divergence took place where the series of vertebrates may have been developed out of the invertebrates. Here he adopts the investigations of A. Kowalewsky, and the deductions of Haeckel founded upon them, concerning the larva of the ascidiae, a genus of marine mollusca of the order tunicata, and sees in a cord, to be found in this larva, most decided relationship to the spine of the lancelet fish or amphioxus, the lowest of all the vertebrates, it being yet doubtful whether it belongs at all to the vertebrates. In the transition that once took place from one species of ascidian larva to a form similar to the lancelet fish, he sees the new branch diverging in the series of vertebrates. Out of the fish he concludes that the amphibia were developed, and out of those the reptilia, out of one of them the marsupialia, and from them the lemurs or half-apes, the representatives of which yet live in Madagascar and the southern part of Asia. From these there branched off on the one side the platyrrhini, or apes with a flat nose, on the new continent; on the other, the catarrhini, or apes with a narrow nose, on the old. Among the ancestor of the last, he searches for the common progenitors, from which again two branches started--on the one hand the ignoble branches of the catarrhine species of apes, always remaining lower in {44} development, to which also belong the anthropomorphous apes, like the orang outang and gibbon in Asia, the gorilla and chimpanzee in Africa; on the other hand, that branch which represents the ascent of animals to man.