The book must be read. Even in this second volume an incredible amount of matter is compressed. An introduction, consisting of a hundred and sixty pages of small type, gives us an idea of the new system. This is the first scheme of a real “natural classification” of living things. From this we pass to special morphology. But this fearless sketch of the specialised genealogical tree, according to the new ideas, puts general morphology in its true light. We are made to feel that it is not all mere theory. To-morrow—nay, to-day—the whole practice of zoology and botany will have to be remodelled on the new principles. Off with the roof of the ark! The whole museum must be cleared out. We want new divisions, new labels. The old controversy between the Nominalists and the Realists seemed to have come to life once more. How students had played with the word “affinity” as a symbol. The lemurs were “related” to the apes, and to other groups of mammals. The star-fishes were related to the sea-urchins, to the encrinites. The word had, in fact, led to a certain amount of arrangement; the stuffed or dried or preserved specimens in the museum were placed side by side. Suddenly the whole thing became a reality. The things that were “related” to each other had really been connected historically in earlier ages. The lemurs were the progenitors of the apes. Behind them were a series of other mammals. Star-fishes, sea-urchins, and encrinites, formed a definite branch of the great tree, and were historically connected; not symbolically, but in a real extinct common ancestor.