. The cell in development and inheritance. Cells. INTRODUCTION 13 fers its hereditary tendencies from generation to generation, at first unchanged, and always uninfiuenced in any corresponding manner, by that which happens during the life of the individual which bears it. If these views be correct, all our ideas upon the transformation of species require thorough modification, for the whole principle of evolution by means of exercise (use and disuse) as professed by La- marck, and accepted in some cases by Darwin, entirely collapses " (/. p. 69). ^t is impossible, he continues, that ac
. The cell in development and inheritance. Cells. INTRODUCTION 13 fers its hereditary tendencies from generation to generation, at first unchanged, and always uninfiuenced in any corresponding manner, by that which happens during the life of the individual which bears it. If these views be correct, all our ideas upon the transformation of species require thorough modification, for the whole principle of evolution by means of exercise (use and disuse) as professed by La- marck, and accepted in some cases by Darwin, entirely collapses " (/. p. 69). ^t is impossible, he continues, that acquired traits should be trans- mitted, for it is inconceivable that definite changes in the body, or "soma," should so affect the protoplasm of the germ-cells as to cause corresponding changes to appear in the offspring. How, he asks, can the increased dexterity and power in the hand of a trained piano- player so affect tlie molecular structure of the germ-cells as to pro- duce a corresponding development in the hand of the child ? It is a physiological impossibility. If we turn to the facts, we find, Weis- mann afifirms, that not one of the asserted cases of transmission of acquired characters will stand the test of rigid scientific scrutiny. It is a reversal of the true point of view to regard inheritance as taking- place from the body of the parent to that of the child. The child inherits from the parent gcnn-ce/l, not from the parent-body, and the germ-cell owes its characteristics not to the body which bears it, but to its descent from a preexisting germ-cell of the same kind. Thus the body is, as it were, an offshoot from the germ-cell (Fig. 5). As ^ Line of â *" (^j Line of inheritance. Fig. 5. â Diagram illustrating Weismann's theory of inheritance. G. The germ-ceil, which t)y division gives rise to the body or soma {S) and to new germ-cells (G\ which separate from the soma and repeat the process in each successive generation. far as inheri
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