. L'étude de la vie animale [microform]. Zoologie Zoologie ;. CHAP. XII Le Life-History d'animaux 203 si nous nous demandons pourquoi un animal développe une notochorde seulement de l'avoir remplacé rapidement par un backbone, une partie de la réponse est sûrement que la notochorde qui dans l'évolution historique a fourni l'impulsion nécessaire à l'élaboration d'un backbone est encore nécessaire dans l'histoire individuelle pour le même but mais il ne fait aucun doute que l'idée de récapitulation est très utile, un m ce qui concerne notre propre histoire ainsi qu'en ce qui concerne les animaux, et nous ferions bien d'y penser beaucoup, et à lire

• Contributeur: The Book Worm / Alamy Banque D'Images
• ID de l’image: RENXKH
• Taille du fichier: 7,2 MB (348,1 KB Téléchargement compressé)
• Autorisations: Modèle - non | Propriété - non
• Dimensions: 797 x 3138 px | 6,7 x 26,6 cm | 2,7 x 10,5 inches | 300dpi

Informations supplémentaires

Cette image appartient au domaine public, ce qui signifie que le droit d’auteur a expiré ou que le titulaire du droit d’auteur a renoncé à ses droits. Les frais facturés par Alamy couvrent l’accès à la copie haute résolution de l’image.

Cette image peut avoir des imperfections car il s’agit d’une image historique ou de reportage.

. The study of animal life [microform]. Zoology; Zoologie. CHAP. XII The Life-History of Animals 203 if we ask why an animal develops a notochord only to have It rapidly replaced by a backbone, part of the answer surely IS that the notochord which in the historical evolution supplied the stimulus necessary for the development of a backbone is still necessary in the individual history for the same purpose But there is no doubt that the idea of recapitulation is a very helpful one, m regard to our own history as well as in regard to animals, and we would do well to think of it much, and to read how Herbert Spencer {Principles of Bw/ogy Land. 1864-66) has discussed it in harmony with his general formula of evolution as a progress from the homo- geneous to the heterogeneous ; how Haeckel {Generelie Mor- pho/o^e Berhn, 1866) has illustrated it, and pithily summed It up in his "fundamental law of biogenesis » {Biogenetisches Grundgesetz saying tha. ontogeny (individual develop- ment) recapitulates phylogeny (racial history); how Milnes Marshall (see Nature, Sept. 1890) has recently tested and criticised It, defining the limits within which the notion can be regarded as true, and searching: for a deeper rationale of the facts than the theory supplies. id) Organic Continuity. In a subsequent chapter on heredity, which simply means the relation of organic continuity between successive generations, I shall explain the fundamental idea that the reproductive cells owe their powtr of developing, and of developing into organisms like the parents, to the fact that they are in a sense continuous with those which gave origin to the parents. A fertilised egg-cell with certain qualities divides and forms a "body" m which these qualities are expressed, distributed, and altered m many ways by division of labour. But it also forms reproductive cells, which do not share in the up- building of the body, which are reproductive cells in fact because they do not do so, becaus

Recherche dans la banque de photos par tags

• bookcentury1900
• bookdecade1900
• booksubjectzoology
• bookyear1902