salamander; on the fifteenth, the purely hypothetical primaeval amniota or protamnia (amnion is the name given to the chorion which surrounds the germ-water and embryo of the three higher classes of vertebrates) on the sixteenth, the primary mammals (promammalia), to which the present monotremes (ornithorhynchus and echidna) stand nearest; on the seventeenth, the pouched animals or marsupialia; on the eighteenth, the semi-apes or prosimiae (loris and maki); on the nineteenth, the tailed apes, or menocerca (nose-apes and slender-apes, or semnopithecus); on the twentieth, the man-like apes (anthropoides) or tail-less catarrhini (gorilla, chimpanzee, orang outang and gibbon). And now we come to twenty-one--ape-like men or speechless primaeval men (alali)--of whom we are reminded to-day by the deaf, and dumb, the cretins and the microcephali; and number twenty-two is _homo sapiens_, the man. The Australians and the Papuans are supposed to be the only remaining representatives of his first stage-development. In like manner, Haeckel also gives us the stem-branches of all the types, classes and orders of the organisms, and forms from them a very acceptable hypothetical pedigree; or--if we prefer to suppose a polyphyletic rather than a monophyletic origin of species--hypothetical pedigrees of the whole organic world. The perspicuity and clearness of Haeckel's deductions, the extent of his knowledge, and the singleness of his aim, to which he makes them all subservient, lend {50} to his works a great charm. But on the other hand we dare not conceal that, even on the ground of explanations belonging purely to natural history, the character of hypothesis is often lost in that of arbitrariness and of the undemonstrable. Even the unlearned in natural science often enough get this impression when reading his works, and will find it confirmed by scientists who not only contradict his assertions in many cases, but disclose plain errors in his drawings--errors, indeed, exclusively in favor of the unity-hypothesis; and in other cases they show that drawings which are given as pictures of the real, represent merely hypothetical opinions. There is especially evident in his works an extremely strong tendency to impress on his hypotheses the character of an established and proved fact, by giving them the alluring name of laws. Entire systems of laws of the selection theory are produced, and all imaginable assertions are also immediately called laws. For example, Huxley, in his anatomical investigations of apes and men, arrives at the conclusion that the differences between the highest and the lowest apes are greater than the differences between the highest apes and man. This purely anatomical comparison, Haeckel calls repeatedly "Huxley's Law." We are well aware that the idea of law is capable of great extension in meaning, and in that respect we can refer to nothing more instructive than the well-meditated inquiry upon this idea in the "Reign of Law" of the Duke of