At the same time this rapid and impulsive acceptance of Darwin’s theory was not merely a decisive moment in Haeckel’s intellectual development; it was bound to be, even externally, a most important step in his career. The theistic controversy was forced on his attention. It passed out of the province of his inmost life, that had hitherto only been discussed in conversation with intimate friends, into the professional work of his most serious and public occupation—into zoology, into the radiolaria at which he had been working for years. We must realise clearly what it must have meant at that time for a young zoologist, who wanted to do rigorous professional work and had quickly decided to settle at Jena in order to begin his career as an official teacher, to become “a Darwinian” in conviction and open confession. It might cost him both his official position and his scientific future; and this at the very moment when he had just secured them, or was in a better position to secure them. We have here for the first time the open manifestation of a principle in Haeckel’s life that he had hitherto only used inwardly, in application to himself. The truth must be told, whatever it cost. Shoot me dead, morally, materially, or bodily, as you will: but you will have to shoot the law first. Darwin’s ominous book had been available in Bronn’s translation for two years. The German professional zoologists, botanists, and geologists almost all regarded it as absolute nonsense. Agassiz, Giebel, Keferstein, and so many others, laughed until they were red in the face, like a riotous first-night public that has made up its mind as to the absurdity of the play from the first act, and torment the author as the cat torments a mouse. Then Haeckel gave to the world his long-prepared _Monograph on the Radiolaria_ (1862), the work with which he endeavours to establish—in fact, must establish—his position as an exact investigator, even amongst the academic scholars of the opposite camp. All goes very smoothly for many pages of the work. A few traces of heresy may be detected about page 100. The passage deals with the relation of organ to individual, in connection with the social species of radiolaria that live in communities. It is a subject that Haeckel took up with great vigour later on, as we shall see. Here it affords him an opportunity to say a word about the general fusion of things in the world of life, in opposition to our rigid divisions in classification. Organ and individual pass into each other without any fixed limit. That, he says, is only a repetition of the relation of the plant to the animal. We cannot establish any fixed limitations between them. What we set up as such are only man’s abstractions. In nature itself we never find these subjective abstract ideas of limitation “incorporated purely, but always fading away in gradual transitions; here, again, the scale of organisation rises gradually from the simplest to the most complex, in a