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Thremmatology

evolution, selection, animals, functional, variation and nature

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THREMMATOLOGY. A term proposed by Ray Lancaster (from the Greek thremma, a nursling) to cover the principles and practices connected with the improvement of domesti cated animals and plants. It is distinct from evolution in general in that its ultimate purpose is utilitarian. The breeder is interested in definite results, whereas nature is supposed to be indifferent to everything but the usurvival of the fittest.° The purpose then in thremma tology is not to make the creature "fie the con ditions of life, but rather to bring both the creature and conditions to harmonize with the highest needs and purposes of man.

This brings to the surface in thremmatol ogy, as a question of prime importance, one that is curious rather than otherwise in evolu tion, namely: Can the conditions of life be employed directly to influence deviation in the desired direction independently of selection; in other words, can individual modification be come hereditary, or as the expression goes in general evolution. arc acquired characters in herited? All studcnts agree that the development of individuals is strongly modified by the condi tions of life, that is, the environment. Out in nature if these modifications are not inherited it implies only a little more work for selection, and the final result is the same whether they are inherited or not. The answer to the ques tion is interesting, therefore, rather than vital so long as the study is confined to general evolution; but in thremmatology the answer involves a vital principle because the breeder, especially of animals, cannot afford unlimited selection. All the animals represent money. and the owner is interested in getting results with a minimum destruction of values. He is in terested, too, in securing improvements as rapidly as possible, because time is money, and man cannot afford the "countless ages* of nature. If, therefore, individual modifications are inherited, even to the slightest degree, the effect is rapidly cumulative, much time is gained and the necessity for selection is largely re duced,— both important considerations from a business standpoint. Upon the answer to this

question will depend the kind of soil and climate employed in plant breeding, the daily care, the shelter, the amount and character of feed pro vided for breeding animals, as well as the mat ter of exercise and training where speed or in telligence are involved. That these are import ant in the development of the individual all are agreed, but it is also necessary that they be provided for breeding stock for the sake of the offspring? Evolutionists in general are interested prima rily in forin, while the thremmatologist is con cerned very largely, if not mainly, with func tion. The size or shape of the cow is of less importance than her ability to convert large amounts of feed into milk and do it econom ically. This faculty depends directly upon the functional ability of a very limited portion of the body and not so much upon the general form. The ability of the horse to attain high speed depends not only upon his conformation but quite as much upon the aquality') of his motor Darts, whether active or sluggish, and the mental make-up, whether well balanced or erratic. Functional activity is, therefore, of much more interest in thremmatology than in general evolution, and functional variation is recognized as one of the principal opportunities for improvement.

The systematic study of thremmatology in volves the following topics: 1. A worlcing knowledge of the ordinary theories and concepts of general evolution.

2. The kinds of variation; namely, qualita tive, relating merely to size; meristic, relating to pattern; and functional, relating to organic activities.

3. Continuous variation in which all values are presented for selection, and discontinuous variation in which some values seldom or never occur, as in the case of sports, iri polymor phism and as it is involved in the idea of orthogenesis.

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