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Rh (correctly) with Horace's “rugosus frigore pagus” (Epist. i. 18, 104). An inscription of the Christian period, found at S Cosimato, speaks of the Massa Mandelana (Corp. Inscr. Lat. xiv. 3482). About 3 m. up the valley, close to the road on the west (right) bank of the stream, are traces of a Roman dwelling-house in opus reticulatum with remains of two mosaic pavements; this is generally identified with the villa of Horace, and probably corresponds fairly closely with its site. That the Fons Bandusiae was near the Sabine farm is not a necessary inference from Od. iii. 13, in which alone it is mentioned; though the scholiasts state it; indeed a fountain of this name near Venusia is mentioned in a bull of 1103. On the other hand, that there was an abundant fountain near the Sabine farm is clear from Epist. i. 16. 12, and Sat. ii. 6. 2. It is generally identified with the Fonte dei Ratini, but the spring of Vigna la Corte, a little farther north, is still more plentiful. Some have supposed that the site of the villa was higher up the hillside, above Rocca Giovane. For Horace speaks of having written Epist. i. 10 “post fanum putre Vacunae,” and an inscription recording a temple of Victoria restored by Vespasian was copied at Rocca Giovane in the 16th century (Corp. Inscr. Lat. xiv. 3485). The identification of Victoria with the Sabine goddess Vacuna is not, however, absolutely certain: and there is here, as elsewhere in Roman literature, a play on the connexion of the name with vacare, “to take a holiday.” In any case, the site of the Sabine farm can be approximately, if not exactly, fixed as in the neighbourhood of Rocca Giovane.

See T. Berti, La Villa di Orazio (Rome, 1886); G. Boissier, Nouvelles promenades archéologiques (Paris, 1886).

(T. As.)  VARIATION AND SELECTION, in biology. Since the publication in 1859 of Charles Darwin's Origin of Species, the theory of evolution of animals and plants (see ) has rested on a linking of the conceptions of variation and selection. Living organisms vary, that is to say, no two individuals are exactly alike; the death-rate and the multiplication-rate are to a certain extent selective, that is to say, on the average, in the long run, they favour certain variations and oppress other variations. Co-operation of the two factors appears to supply a causal theory of the occurrence of evolution; the suggestion of their co-operation and the comparison of the possible results with the actual achievements of breeders in producing varieties were the features of Charles Darwin's theoretical work which made it a new beginning in the science of biology, and which reduced to insignificance all earlier work on the theory of evolution. P. Geddes, J. H. Stirling, E. Clodd and H. F. Osborn have made careful studies of pre-Darwinian writers on evolution, but the results of their inquiries only serve to show the greatness of the departure made by Darwin.

Several of the ancients had a vague belief in continuity between the inorganic and the organic and in the modifying or variation-producing effects of the environment. Medieval writers contain nothing of interest on the subject, and the speculations of the earliest of the modern evolutionists, such as C. Bonnet, were too vague to be of value. G. L. L. Buffon, in a cautious, tentative fashion, suggested rather than stated the mutability of species and the influence of the forces of nature in moulding organisms. Immanuel Kant, in his Theory of the Heavens (1755), foreshadowed a theory of the development of unformed matter into the highest types of animals and plants, and suggested that the gradations of structure revealed by comparative anatomy pointed to the existence of blood relationship of all organisms, due to derivation from a common ancestor. He appeared to believe, however, that the successive variations and modifications had arisen in response to mechanical laws of the organisms themselves rather than to the influence of their surroundings. J. G. von Herder suggested that increase by multiplication with the consequent struggle for existence had played a large part in the organic world, but his theme remained vague and undeveloped. Erasmus Darwin, the grandfather of Charles Darwin, set forth in Zoonomia a much more definite theory of the relation of

variation to evolution, and the following passage, cited by Clodd, clearly expresses it:—

“When we revolve in our minds the metamorphoses of animals, as from the tadpole to the frog; secondly, the changes produced by artificial cultivation, as in the breeds of horses, dogs and sheep; thirdly, the changes produced by conditions of climate and season, as in the sheep of warm climates being covered with hair instead of wool, and the hares and partridges of northern climates becoming white in winter; when, further, we observe the changes of structure produced by habit, as shewn especially by men of different occupations; or the changes produced by artificial mutilation and prenatal influences, as in the crossing of species and production of monsters: fourth, when we observe the essential unity of plan in all warmblooded animals—we are led to conclude that they have been alike produced from a single living filament.”

G. R. Treviranus, in the beginning of the 10th century, laid stress on the indefiniteness of variation, but assumed that some of it was adaptive response to the environment, and some due to sexual crossing. J. B. P. Lamarck was the first author to work out a connected theory of descent and to suggest that the relationships of organic forms were due to actual affinities. He believed that life was an expanding, growing force, and that animals responded to the environment by developing new wants, seeking to satisfy these by new movements and thus by their own striving producing new organs which were transmitted to their descendants. Variation was in fact a purposive response.

In 1813 W. C. Wells definitely propounded the theory of natural selection, but applied it only to certain human characters. In 1831 Patrick Matthew, in the appendix to a book on naval timber and arboriculture, laid stress on the extreme fecundity of nature “who has in all the varieties of her offspring a prolific power much beyond (in many cases a thousandfold) what is necessary to fill up the vacancies caused by senile decay. As the field of existence is limited and preoccupied, it is only the hardier, more robust, better-suited-to-circumstance individuals, who are able to struggle forward to maturity, these inhabiting only the situations to which they have superior adaptation and greater power of occupancy than any other kind; the weaker and less circumstance-suited being prematurely destroyed. This principle is in constant action; it regulates the colour, the figure, the capacities and instincts; those individuals in each species whose colour and covering are best suited to concealment or protection from enemies, or defence from inclemencies or vicissitudes of climate, whose figure is best accommodated to health, strength, defence and support; whose capacities and instincts can best regulate the physical energies to self-advantage according to circumstances—in such immense waste of primary and youthful life those only come to maturity from the strict ordeal by which nature tests their adaptation to her standard of perfection and fitness to continue their kind by reproduction.” G. St Hilaire and afterwards his son Isodore regarded variation as not indefinite but directly evoked by the demands of the environment. L. von Buch laid stress on geographical isolation as the cause of production of varieties, the different conditions of the environment and the segregated interbreeding gradually producing local races. K. E. von Baer and M. J. Schleiden regarded variation and the production of new or improved structures as an unfolding of possibilities latent in the stock. Robert Chambers, in the once famous Vestiges of Creation, interested and shocked his contemporaries by 'his denial of the fixity of species and his insistence on creation by progressive evolution, but had no better theory of the cause of variation than to suppose that organisms—“from the simplest and oldest to the highest and most recent” were possessed of “an inherent impulse, imparted by the Almighty both to advance them from the several grades and modify their structure as circumstances required.” In 1852 C. Naudin compared the origin of species in nature with that of varieties under cultivation. Herbert Spencer from 1852 onwards maintained the principle of evolution and laid special stress on the moulding forces of the environment which called into being primarily new functions and secondarily new structures. 