. An examination of Weismannism [microform]. Heredity; Evolution; Hérédité; Evolution. t ft I'i ! â I ! r' I ,; ; lii in Jo t. 6VVt,*+V1^^4^< 20 y^« Examination of Wcismannism. all in the process of organic evolution. No matter how many generations of eagles, for instance, may have used their wings for purposes of flight ; and no matter how great an increase of muscularity, of endurance, and of skill, may thus have been secured to each genera- tion of eagles as the result of individual exercise ; all these advantages are entirely lost to progeny, and young eagles have ever to begin thei
. An examination of Weismannism [microform]. Heredity; Evolution; Hérédité; Evolution. t ft I'i ! â I ! r' I ,; ; lii in Jo t. 6VVt,*+V1^^4^< 20 y^« Examination of Wcismannism. all in the process of organic evolution. No matter how many generations of eagles, for instance, may have used their wings for purposes of flight ; and no matter how great an increase of muscularity, of endurance, and of skill, may thus have been secured to each genera- tion of eagles as the result of individual exercise ; all these advantages are entirely lost to progeny, and young eagles have ever to begin their lives with no more benefit bequeathed by the activity of their ancestors than if those ancestors had all been barn- door fowls. The only material which is of any count as regards the species, or with reference to the piOgess of evolution, are fortuitous variations of the congenital k[nd. Among all the numberless congenital varia- tions, within narrow limits, which are perpetually occurring in each generation of eagles, some will have reference to the wings ; and although these will be fortuitous, or occurring indiscriminately in all direc- tions, a few of them will now and then be in the direction of increased muscularity, others in the direction of increased endurance, others in the direc- tion of increased skill, and so on. Now each of these fortuitous variations, which happens also to be a beneficial variation, will be favoured by natural selection ; and, because it likewise happens to be a congenital variation, will be perpetuated by heredity. InTthe course of time, other congenital variations will happen to arise in the same directions; these will be added by natural selection to the advantage already gained, and so on, till, after hundreds and thousands of generations, the wings of eagles have become evolved into the marvellous structures which they now present. Such being the theory of natural selection when. Please note that these images are extracted from sc
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherchicagoopencourtpu
