unscientific and a popular superstition. The young doctor, duly initiated into these ideas of the time, could not resist the temptation to give his own kick to the fallen theory. Yet how strangely things have changed since then! Two years afterwards Haeckel ceased to believe in a special vital force; he was now absolutely convinced that there were unicellular beings; his whole theory of life seemed to demand spontaneous generation as a postulate, and he even doubted the force of the experiments of Schwann and others. Haeckel himself became the keenest apostle of the theory of spontaneous generation. Whenever it is mentioned to-day, we think of the weight of his name which he has cast in the scale in its favour. So the leaves change even in the forest of science: yesterday green, to-day red and falling, to-morrow green once more. On the same branch as the dogmas we find the correctives growing, that will at length split them open and cast them as empty husks to the ground. The history of Haeckel’s medical doctorate can be written in a few plain and touching lines. After receiving his degree he was sent by his prudent father, to keep him away from crabs and other monsters of the deep, to Vienna for a term, to do hospital work under Oppolzer, Skoda, Hebra, and Siegmund. All that we find recorded of this term is that his old love of botany revived in earnest. Immense quantities of dwarf Alpine plants were collected. When the traveller passed by the spot twenty-four years afterwards on a quiet autumn Sunday, on his way to take ship at Trieste for the tropical forests and giant trees of Ceylon, the memory of Schneeberg and the Rose-Alp came upon him like a dream. However, the hospital work, together with a short span of cramming in the winter at Berlin, must have had some effect, as he passed the State-examination in medicine. In March, 1858, he was a “practising physician.” He had in his hand the crown of prudent ambition—and he felt like a poor captive. There was one source of consolation—Johannes Müller. While one was near him there was a possibility of more real work. He discussed with him the plan of the study of the development of the gregarinæ (parasitic protozoa), which he wanted to conduct in Müller’s laboratory in the summer of 1858. Then he was stricken, like so many others, with the thunderbolt of the news of Müller’s sudden death, on April 28th of the same year. What must he do now? He began to practise. It is said on his own authority that he fixed the hours of consultation from five to six in the morning! The result was that during a whole year of this philanthropic occupation he had only three patients, not one of whom died under his earnest attention. “This success was enough for my dear father,” says Haeckel. We can well believe it.