Then came Darwin’s _Naturalist’s Voyage round the World_. The ardent youth had as yet on suspicion what the name would one day mean to him. Darwin was then regarded as a completed work on which final judgment had been rendered. He was appreciated as a traveller, a student of the geology of South America, and especially as the gifted investigator of the wonderful coral reefs of the Indian Ocean. His name stood thus in all the manuals, close even to that of Humboldt. Probably the young reader thought he had died long before. At all events, no one had a presentiment that this quiet naturalist and student of corals was about to light a torch that would flame over the world. The chief advantage that Haeckel drew from the two works was an ardent desire to see the tropics, with their virgin forests and blue coral seas. It has come to so many after reading these works, and persisted in their lives as the vivid image of a dream, like that which drove Goethe to Italy—the dream of a home of the soul that must one day be sought. The third book was Schleiden’s _The Plant and its Life_. Matthias Jacob Schleiden was then in the best of his power, and had an influence that amounted to fascination on many of the younger men. Behind him lay a terrible struggle. He had begun his career as a lawyer, and had been so unfortunate that he even attempted his life. With his interest in botany a new life began, and he worked with the energy of one raised from the dead. He was certainly an original thinker. His name is known to us to-day especially as the founder of the cell-theory. This is the greatest distinction that he has earned. But at that time he had a much more general importance as a leader in the struggle to introduce a certain method of scientific research. A somewhat obscure epoch was coming to a close, a more or less superficial natural philosophy having sought to replace sound investigation. The struggle had ended with the decisive victory of the simple discovery of facts. There was everywhere a vague feeling that the progress of science was best secured by a bald enumeration and registration of bones, of the joints in the limbs of insects, or of pollen-filaments, rather than by the romantic and spirited leaps of natural philosophy over all the real problems into the heavens above. The question now arose whether this narrow method really exhausted the nature of things; whether scientific specialism, with its laurels of victory, would not prove in the end an equally dangerous enemy. What was “better” for the time being might be very far from really “good.” It was here that Schleiden stepped in. He fought against the prevailing specialism, at first in his own particular province of botany. He did not, indeed, take up the cause of the exploded pyrotechnics of the older natural philosophy, but pleaded for more general critical-philosophical methods. These must be preserved in any circumstances. The great botanist, he said, is not the man who can