had been produced by budding from the product of a single egg-cell.  This subtle analysis of ideas delighted and interested his contemporaries, and the train of logical examination of what is meant by individuality has persisted to the present time.  Like all other zooelogical ideas, this has been considerably altered by the conception of evolution.  Zooelogists no longer attempt to stretch logical conceptions until they fit enormous and different parts of the living world.  They recognise that the living world, because it is alive, is constantly changing, and that living things pass through different stages or kinds of individuality in the course of their lives.  A single egg-cell is one kind, perhaps the simplest kind, of zooelogical individual; when it has grown up into a simple polyp it has passed into a second grade of individuality; when, by budding, the polyp has become branched, a third grade is reached, and when the branches have become different, in obedience to the different purposes which they are to serve in the whole compound creature, a still further grade is reached.  Huxley’s attempt to find a meaning for individuality that would apply equally to a single simple creature, to a compound creature, and to the large number of separate creatures, all developed by budding from one creature, is a striking instance of his singular capacity for bringing apparently dissimilar facts into harmony, by finding out the common underlying principle, and, although we no longer accept this particular conclusion, we cannot fail to notice in it the peculiar powers of his mind.

A second and even more interesting Royal Institution lecture dealt with the “Identity of Structure in Animals and Plants.”  At the present time every educated person knows that the life of animals and plants alike depends on the fact that their bodies are composed of a living material called protoplasm, a material which is identical in every important respect in both kingdoms of the living world.  In the early fifties, scientific opinion was by no means clear on this matter, and certainly public opinion was most vague.  Huxley discussed what was meant by organisation, and shewed that in every essential respect plants and animals alike were organised beings.  Then he went on to explain the cellular theory of Schwann, which was then a novelty to a general audience.  Schwann, in studying the microscopic structure of plants, noticed that their bodies were made up of little cases with firm walls; these he called cells, and declared that the whole body of the plant was composed of cells.  As the walls of these cells were the most obvious and visible feature, it was supposed that they were the most essential part of the structure, and there was some difficulty in applying the cellular theory to the bodies of animals, as in most cases there are no easily visible cell-walls in animal tissues.  As the result of his own observation, and from his reading of the work of others, Huxley