The vital principle or efficient cause of motion and action, in the animal and vegetable[4] system, perhaps, may be more similar than we generally apprehend. Where is the essential difference between the seed of peas, peaches and other tribes of plants and trees, and the eggs of oviparous animals, as the eggs of birds, snakes, or butterflies, spawn of fish, &c.? Let us begin at the source of terrestrial existence. Are not the seed of vegetables, and the eggs of oviparous animals fecundated, or influenced with the vivific principle of life, through the approximation and intimacy of the sexes? and immediately after the eggs and seeds are hatched, does not the young larva and infant plant, by heat and moisture, rise into existence, increase, and in due time arrive to a state of perfect maturity? The physiologists agree in opinion, that the work of generation in viviparious animals, is exactly similar, only more secret and enveloped. The mode of operation that nature pursues in the production of vegetables, and oviparous animals, is infinitely more uniform and manifest, than that which is or can be discovered to take place in viviparous animals. The most apparent difference between animals and vegetables is, that animals have the powers of sound, and are locomotive, whereas vegetables are not able to shift themselves from the places where nature has planted them: yet vegetables have the power of moving and exercising their members, and have the means of transplanting and colonising their tribes almost over the surface of the whole earth; some seeds, for instance, grapes, nuts, smilax, peas, and others, whose pulp or kernel is food for animals, will remain several days without being injured in stomachs of pigeons and other birds of passage; by this means such sorts are distributed from place to place, even across seas; indeed some seeds require this preparation by the digestive heat of the stomach of animals, to dissolve and detach the oily, viscid pulp, and to soften the hard shells. Small seeds are sometimes furnished with rays of hair or down, and others with thin light membranes attached to them, which serve the purpose of wings, on which they mount upward, leaving the earth, float in the air, and are carried away by the swift winds to very remote regions before they settle on the earth; some are furnished with hooks, which catch hold of the wool and hair of animals passing by them, are by that means spread abroad; other seeds ripen in pericarpes, which open with elastic force, and shoot their seed to a very great distance round about; some other seeds, as of the Mosses and Fungi, are so very minute as to be invisible, light as atoms, and these mixing with the air, are wafted all over the world.