Animal life and intelligence . characters acquired by the bodycannot be transmitted to the offspring through the ova orsperms. The annexed diagram illustrates how, on theview that the hen produces the egg, dints hammered intothe body by the environment will be handed on; while, onthe view that the hen does not produce the egg, the dintsof the environment are not transmitted to the the hypothesis of continuity, heredity is due to the factthat two similar things under similar conditions will givesimilar products. The ovum from which the mother is * Weismann, Essays on Heredity, p. 1
Animal life and intelligence . characters acquired by the bodycannot be transmitted to the offspring through the ova orsperms. The annexed diagram illustrates how, on theview that the hen produces the egg, dints hammered intothe body by the environment will be handed on; while, onthe view that the hen does not produce the egg, the dintsof the environment are not transmitted to the the hypothesis of continuity, heredity is due to the factthat two similar things under similar conditions will givesimilar products. The ovum from which the mother is * Weismann, Essays on Heredity, p. 179. Heredity and the Origin of Variations. 141 developed, and the ovum from which the daughter isdeveloped, are simply two fragments separated at differenttimes from the same continuous germ-plasm.* Bothdevelop under similar circumstances, and their productscannot, therefore, fail to be similar. How variation ispossible under these conditions we shall have to considerpresently. Now, although I value highly Professor Weismanns. n. Fig. 21.—Egg and hen. I. The egg produces the hen. II. The hen produces the egg. In I. the dints pro-duced by the environment are not inherited ; in IX. they are. The letters indicate successiveindividuals. The small round circles indicate the eggs. luminous researches, and read with interest his ingeniousspeculations, I cannot but regard his doctrine of the con-tinuity of germ-plasm as a distinctly retrograde step. Hisgerm-plasm is an unknowable, invisible, hypothetical though it be, it is of no more practical value thana mysterious and mythical germinal principle. By a littleskilful manipulation, it may be made to account for any- * It will, of course, be understood that a minute fragment of germ-plasmis capable of almost unlimited growth by assimilation of nutritive material,its properties remaining unchanged during such growth. j42 Animal Life and Intelligence. thing and everything. The fundamental assumption thatwhereas germ-plas
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