It is true that this section, which essays to compress all living things into a very simple scheme, is the hardest to read in the whole work. A number of strange and difficult words have to be invented for this stereometric scheme to which he would reduce the animal and plant forms. Haeckel himself declared, twenty years afterwards (in the second part of the _Monograph on the Radiolaria_), that this stereometry of organic forms had found little favour in biology “especially on account of the difficult and complicated nomenclature.” But he had complete confidence as to the substance of it, even after so great a lapse of time. In point of fact we have here, it seems to me, a gigantic preparatory work, not so much for the strict purpose of classification, as for a real philosophy of botany and zoology that will be founded some day. This recurrence of sharp stereometric structures, not only in the crystal, but also, if less clearly, in the biological world, will one day prove an important source of knowledge, in a sense that is not even clear in Haeckel himself. We are already entering upon a period that has a glimpse of the truth that the deepest power of Beethoven’s music, or Goethe’s poetry, or Raphael’s painting, or Michael Angelo’s sculpture is a mysterious revelation of the most subtle mathematical relations and effects—produced without conscious perception of these relations, though a human mind is at work in them. In spite of all our “consciousness,” the obscure intuitive power at work in these human artistic achievements differs very little from the curious force with which a radiolarian builds up its little house in the deep-sea or a caseworm fits on its fine, rhythmic, snail-like coat. In both we have the same profound, crystal-like constructive power that brought forth the wings of the butterfly, the feathers of the bird, the bodily frame of all the animals and plants, that harmonises so well with strict mathematical forms. In Beethoven and Raphael it is not more conscious or unconscious, not clearer or vaguer, not more mystical or more natural, than in the poorest worm or the microscopically small radiolarian. The æsthetics of the twentieth century will take up these ideas. * * * * * [Illustration: HAECKEL’S VILLA AT JENA. ]