The individuals composing one of these Siphonophora are so manifestly analogous to organs, that their individuality may, perhaps, be disputed, the more so as they do not live separately. But the gradations of separation are very fine. You would never hesitate to call a bee, or an ant, an individual, yet no bee or ant could exist if separated from its colony. So great is “the physiological division of labour,” which has taken place among these insects, that one cannot get food, another cannot feed itself, but it will fight for the community; another cannot work, but it will breed for the community; another cannot breed, but it will work. Each of these is little more than _separated_ organs of the great insect-Organism; as the heart, stomach, and brain are _united_ organs of the human-Organism. Remove one of these insects from the community, and it will soon perish, for its life is bound up with the whole. And so it is everywhere; the dependence is universal:— “Nothing in this world is single; All things, by a law divine, In one another’s being mingle.” We are dependent on the air, the earth, the sunlight, the flowers, the plants, the animals, and all created things, directly or indirectly. Nor is the moral dependence less than the physical. We cannot isolate ourselves if we would. The thoughts of others, the sympathies of others, the needs of others,—these too make up our life; without these we should quickly perish. It was a dream of the youth Cuvier, that a History of Nature might be written which would systematically display this universal interdependence. I know few parts of biography so interesting as those which show us great men in their early aspirings, when dreams of achievements vaster than the world has seen, fill their souls with energy to achieve the something they do afterwards achieve. It is, unhappily, too often but the ambition of youth we have to contemplate; and yet the knowledge that after-life brought with it less of hope, less of devotion, and less of generous self-sacrifice, renders these early days doubly interesting. Let the abatement of high hopes come when it may, the existence of an aspiration is itself important. I have been lately reading over again the letters of Cuvier when an obscure youth, and they have given me quite a new feeling with regard to him.