It was necessary, in order that Darwin should persuade other naturalists that his views were correct, that he should show by putting examples “on the table” that variations occur naturally and in great diversity; further, that there is great pressure in the conditions of life, and a consequent survival of the best-suited varieties; further, that there is in reproduction a transmission of the peculiar favouring character or quality which enables a variety to survive, and thus a tendency to perpetuate the new quality. It was not enough for Darwin to “imagine” that these things might be so, or to make the notion that they are so plausible by arguments drawn from existing knowledge. He had to do that: but also he had to make new inquiries and discover new things about animals and plants which fitted in with his theory and would not fit in either with the notion that all plants and animals were created—as the poet Milton supposed—out of lumps of earth and muddy water, suddenly, in the likeness of their present-day descendants, nor with some other notions, such as that of the able and gifted French naturalist Lamarck. And he spent the later twenty years of his life in doing so, just as he had spent the previous twenty years in collecting a first series of facts and observations justifying his theory before he announced it to the world. A great difference between Lamarck and Darwin exists, not only in their two theories as to the mode of origin of the vast diversified series of kinds or species of plants and animals, but in their way of stating and dealing with the theory which each thought out and gave to the world. Lamarck had a great knowledge of the species of plants and animals, partly through having collected specimens himself when he was an officer in the French Republican army which was employed on the Mediterranean shores of France and Italy more than a hundred years ago, and partly through his later official position in the great natural history museum at Paris, where large collections passed through his hands. He was a man of very keen insight and excellent method, and did more to plan out a natural and satisfactory “classification” of animals than any one between his own day and that of Linnæus. His theory of the origin of species was essentially an opposition to the then popular view that the species of living things have been made by the Creator so as to fit the conditions in which they live. Lamarck contradicted this view, and said in so many words that the real fact is that the peculiar specific characters of animals or of plants have not been created for their conditions, but, on the contrary, that the conditions in which they live have created the peculiarities of living things. In so far his conception was the same as Darwin’s. But Lamarck then said to himself: How do the conditions create the peculiarities of different living things? And he answered this question by an ingenious guess, which he