It seems as though in many, indeed in most instances, a life current, instead of driving on towards either greater freedom or complete arrest, met with a resistance able to constrain it, as it were, into eddies, wherein it circles as creatures living out either in a relative independence or in a parasitic state (sometimes of primary development, at others of degradation from a higher mode) their restricted lives. They are being fulfilled according to their restricted wants; they are needing no more of life than they have, and therefore seek no further than they are. And they have their co-operative value in the whole. These are the minor, yet many of them—and that in spite of dangers and pain and death—the delightful, successes of life. Everywhere upon this earth now, it seems, except in man, we may justly picture the life-currents as either coming to an end or circling round and round in some such eddy, at most curving out a little way to change a little in shape, to form new varieties within a species or, rarely, new species within a genus. There is in lower animals than ourselves, and in the plants, a certain contentment, on which tired men have sometimes been known to look with envy. The realm of nature is well served by servants such as these, and natural delights, in spite of natural pains, are won. But not all that life can do and be is represented in those finished forms. In the plants it seems to be asleep. There the protoplasmic stuff has built a wall about its soft body, the casing of cellulose behind which it sleeps, working in sleep, in great measure cut off from the varied stimulus and many-tongued summons, the resistances and opportunities, of an outer world. And some of the animals that are now extinct owe their extinction, not to their gigantic size, but to their having sought safety rather than adventure, and imprisoned themselves in their mechanical armour of defence. They too were in their measure cut off from the stir and help and moving oppositions of associated lives. In truth and in regard to the supreme purpose manifested in life, all the non-human creatures of the earth have, within themselves and for themselves, in one fashion or another barred its advance; although very many of them are furthering its purposes, indeed giving them indispensable support, elsewhere. Those which have not been extinguished and still maintain their place in the world are too complete, too well-adapted to a satisfying but narrow sphere, for progress to a wider. Life is not bearing them on; their nervous organ, that structure of inter-related cells by which they use their world, selecting and determining this or that, has not like ours capacity for indefinite change. Theirs is exactly fitted for their narrow use of it, and they and it are constrained together.