in Zoonomia, "Intuitive Analogy," Vol. I. Sect. XVII. 7. The novelty of any idea, may be confidered as affecting us with another kind of furprise, or incongruity, as it differs from the ufual train of our ideas, and forms a new link in this perpetual chain; which, as it thus differs from the ordinary course of nature, we inftantly examine by the voluntary efforts of intuitive analogy; or by reafoning, which we attend to; and compare it with the usual appearances of nature. These ideas which affect us with furprise, or incongruity, or novelty, are attended with painful or pleasureable fenfation; which we mentioned before as intermixing with all catenations of animal actions, and contributing to ftrengthen their perpetual and energetic production; and alfo exciting in fome degree the power of volition, which also intermixes with the links of the chain of animal actions, and contributes to produce it. Now by frequent repetition the furprife, incongruity or novelty ceases; and, in confequence, the pleasure or pain which accompanied it, and also the degree of volition which was excited by that sensation of pain or pleasure; and thus the fenforial power of fenfation and of volition are fubducted from the catenation of vital actions, and they are in confequence produced much weaker, and at length cease entirely. Whence we learn why contagious matters induce their effects on the circulation but once; and why, in process of time, the vital movements are performed with less energy, and at length ceafe; whence the debilities of age, and confequent death. NOTE. VIII.-REPRODUCTION. But Reproduction with ethereal fires I. THE reproduction or generation of living organized bodies, is the great criterion or characteristic which diftinguishes animation from mechanifm. Fluids may circulate in hydraulic machines, or fimply move in them, as mercury in the barometer or thermometer, but the power of producing an embryon which shall gradually acquire fimilitude to its parent, diftinguishes artificial from natural organization. The reproduction of plants and animals appears to be of two kinds, folitary and fexual; the former occurs in the formation of the buds of trees, and the bulbs of tulips; which for several fucceffions generate other buds, and other bulbs, nearly fimilar to the parent, but conftantly approaching to greater perfection, fo as finally to produce fexual organs, or flowers, and consequent feeds. The fame occurs in fome inferior kinds of animals; as the aphides in the fpring and fumer are. viviparous for eight or nine generations, which fucceffively produce living defcendants without fexual intercourse, and are themselves, I suppose, without fex; at length in the autumn they propagate males and females which copulate and lay eggs, which lie dormant during the winter, and are hatched by the vernal fun; while the truffle, and perhaps mushrooms amongst vegetables, and the polypus and tænia amongst infects, perpetually propagate themfelves by folitary reproduction, and have not yet acquired male and female organs. Philofophers have thought these viviparous aphides, and the tænia, and volvox to be females; and have supposed them to have been impregnated long before their nativity within each other; so the tænia and volvox ftill continue to produce their offspring without fexual intercourse. One extremity of the tænia, is faid by Linnæus to grow old, whilst at the other end new ones are generated proceeding to infinity like the roots of grass. The volvox globator is tranfparent, and carries within itself children and grandchildren to the fifth generation like the aphides; fo that the tænia produces children and grandchildren longitudinally in a chainlike feries, and the volvox propagates an offspring included within itfelf to the fifth generation; Syft. Nat. Many microscopic animals, and fome larger ones, as the hydra or polypus, are propagated by fplitting or dividing; and some still larger animals, as oysters and perhaps cels, have not yet acquired fexual organs, but produce a paternal progeny, which requires no mother to fupply it with a nidus, or with nutriment and oxygenation; and, therefore, very accurately resemble the production of the buds of trees, and the wires of fome herbaceous plants, as of knot-grafs and of ftrawberries, and the bulbs of other plants, as of onions and potatoes; which is further treated of in Phytologia, Sec. VII. The manner in which I fufpect the folitary reproduction of the buds of trees to be effected, may also be applied to the folitary generation of the infects mentioned above, and probably of many others, perhaps of all the microfcopic ones. It should be previously obferved, that many infects are hermaphrodite, poffeffing both male and female organs of reproduction, as fhell-fnails and dew worms; but that thefe are seen reciprocally to copulate with each other, and are believed not to be able to impregnate themselves; which belongs, therefore, to fexual generation, and not to the folitary reproduction of which I am now fpeaking. As in the chemical production of any new com bination of matter, two kinds of particles appear to be neceffary; one of which muft poffefs the power of attraction, and the other the aptitude to be attracted, as a magnet and a piece of iron; fo in vegetable or animal combinations, whether for the pur 6 pofe of nutrition or for reproduction, there must exift alfo two kinds of organic matter; one poffeffing the appetency to unite, and the other the propenfity to be united; (fee Zoonomia, octavo edition, Sect. XXXIX. 8.) Hence in the generation of the buds of trees, there are probably two kinds of glands which acquire from the vegetable blood, and depofite beneath the cuticle of the tree two kinds of for. mative organic matter, which unite and form parts of the new vegetable embryon; which again uniting with other fuch organizations form the caudex, or the plumula, or the radicle, of a new vegetable bud. A fimilar mode of reproduction by the fecretion of two kinds of organic particles from the blood, and by depofiting them either internally as in the vernal and fummer aphis or volvox, or externally as in the polypus and tænia, probably obtains in those animals; which are thence propagated by the father only, not requiring a cradle, or nutriment, or oxygenation from a mother; and that the five generations, faid to be seen in the transparent volvox globator within each other, are perhaps the fucceffive progeny to be delivered at different periods of time from the father and erroneoufly fuppofed to be mothers impregnated before their nativity. II. Sexual as well as folitary reproduction appears to be effected by two kinds of glands; one of which collects or fecretes from the blood formative organic particles with appetencies to unite, and the other |