572 PALEONTOLOGY 



in the environment, in the bodies of animals, or in the germinal cells 

 they all ultimately find their way into the germinal cells. They may 

 be summarized as follows: 



(1) Segregation. Besides the familiar geographical segregation of 

 animals, which reaches its highest expression in insular forms, such as 

 the pygmy fossil elephants of Malta 1 and those recently discovered in 

 Cyprus (Bate), 2 there is the no less effective segregation of habit among 

 animals existing in the same geographical regions and under the same 

 climatic conditions, but seeking different varieties of food on different 

 kinds of soil. These give rise to what I have called local adaptive 

 radiations, a principle which explains the occurrence in the same 

 country, and almost side by side, of very conservative as well as very 

 progressive forms. 



(2) Adaptive Modification. This is a plastic principle which tends 

 in the course of life to an increasing fitness of the bodies of individuals 

 to their special environments and habits, well illustrated among men 

 in the influence of various trades and occupations and operating both 

 in active and in passive structures. Consistent with the adaptive modi- 

 fication principle is the fact that every individual requires habit and 

 environment to model it into its parental form ; and in every change 

 of environment or habit every individual is carried an infinitesimal 

 degree beyond the parental form; the wonderful phenomena of cor- 

 related development which puzzled Spencer so much are chiefly at- 

 tributable to this principle. These adaptive modifications are not 

 directly inherited, as Lamarck supposed, but acting through long 

 periods of time there results the organic selection (Morgan, 3 Baldwin, 4 

 Osborn 5 ) of those individuals in which hereditary predisposition 

 happens most closely to coincide with adaptive modification, and 

 there thus finally comes about an apparent, but not real, inherit- 

 ance of acquired characters, as Lamarck, Spencer, and Cope sup- 

 posed. 



(3) Variations of Degree. We should by no means exclude as true 

 causes of evolution associated with both the above factors the selec- 

 tion of those variations of degree or around a mean which conform to 

 Quetelet's curve, the subject of the chief investigations of the Galton 



1 L. Adams, On the Dentition and Osteology of the Maltese Fossil Elephants, 

 Transactions of the Zoological Society, vol. rx, pt. i, 1874. 



2 Dorothy M. A. Bate, Further Note on the Remains of Elephas Cypriotes, 

 Philosophic Transactions of the Royal Society, London, ser. B, vol. 197, 1904, pp. 

 347-360. 



8 C. Lloyd Morgan [Organic Selection], Science, Nov. 27, 1896. 



4 J. Mark Baldwin, A New Factor in Evolution, American Naturalist, June 

 and Julv, 1896; Development and Evolution, 8vo, New York, 1902. 



* H. F. Osborn, A Mode of Evolution requiring neither Natural Selection nor the 

 Inheritance of Acquired Characters (Organic Selection), Transactions of the New 

 York Academy of Science, March and April, 1896, pp. 141-148; The Limits of 

 Organic Selection, American Naturalist, Nov. 1897, pp. 944-951; Modification 

 and Variation and the Limits of Organic Selection, Proceedings, American Asso- 

 ciation for the Advancement of Science, 46th meeting, 1898, pp. 239-242. 



