THE FOUR INSEPARABLE FACTORS OF EVOLUTION. 287 



10. Accommodation or individual adaptation reflected in the above somations 

 arising through plasticity, modifiability, or adaptability to new relations. 



11. The "variations of Darwin" in part, including such fluctuations or 

 changes of degree as are caused by use, disuse, and habit in distinction from 

 those which are caused in the germ. 



12. The "modifications" of Lloyd Morgan. 



13. The "ontogenic variations" of Osborn. 



14. Acquired or individual immunity. 



15. Ontogenic fertility and infertility due to external and internal causes. 



16. Somatic correlations acquired as distinguished from hereditary corre- 

 lations. 



17. Influence of "habitudinal selection," of individual choice, change of 

 food, etc. 



18. Intra-selection (Roux) or struggle between the parts of the organism. 



19. Somatic or ontogenic environment of the germ cells. 



20. Ontogenic balance of organs (St. Hilaire). 



21. Ontogenic compensation of growth (St. Hilaire). 



22. Somation or ontogenic adaptation affording the opportunity for "coin- 

 cident variation" or "organic selection" (Morgan, Baldwin, Osborn). 



23. Functional adaptation (Roux, functionelle Anpassung) . 



24. Physiological or second order correlations (Crampton). 



Summing up all such ontogenic changes, which are partly pure expressions of 

 heredity, partly heredity modified by ontogeny, we secure the following classi- 

 fication: 



Classification of Ontogenic Changes. 



. Normal or typical growth, cytogeny, embryogeny, ontogeny. 



Hereditary Recapitulation of ancestral history, under similar inherited conditions. 



Repetition of J Recapitulation of parental history, inherited conditions. 



Type J Revival of ancestral characters through stimulus of revived ancestral environment. 



(Conserva- Somations through normal physical environment, tradition, incidence of sc Action, 

 tive). [ etc. 



ro 8 ^ men -k s f Somations through abnormal or unfavorable action of physical environment, social 

 (Retrogressive-j relations, traditions, altered sexual relations, conditions of reproduction, etc. 

 and Neutral) . I Fluctuations retrogressive. 



Progressive c 

 Fluctuations 



condition! 



D ,. AUDreviations 01 ancestral nistory due to abbreviation ol 



readjustments J Ontogenic intercalations. 

 (Progressive). 1 Acceleration of ontogeny of certain organs through increased functions. 



Correlation to new conditions. 



Correlation to acquired conditions. 



Neomorphs, neogenesis, new characters. 



Here may be introduced J. Mark Baldwin's definition of modification : 



Modification (in biology) [Lat. modificatio]: Ger. {individual erworbene) Ab&nderung (Wundt); 

 Fr. modification: Ital. modificazione . A structural change wrought during the individual's lifetime 



upward prolongation of the odontoid peg of the axis, and a new accessory transverse ligament to keep it 

 from pressing upon the cord. In short, "the anatomy of the shoemaker represents the fixation and sub- 

 sequent exaggeration of the position and tendencies to change which were present in his body when he 

 assumed the position for a short period of time." (Osborn, H. F., Medical Record, 1892, pp. 35-36.) 



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