404- PALEONTOLOGY 



influences of species of Protozoa.* AVith regard to the species 

 of higher organisms, distinguishable as plants and animals, 

 their origin is as yet only matter of speculation. 



Buffonf regarded varieties as particular alterations of 

 species, which illustrated the mutability of species themselves. 

 The so-called varieties of a species, species of a genus, genera 

 of an order, etc., were with him but so many evidences of the 

 progressive degrees of change, which had been superinduced 

 by time and successive generations, and chiefly by degrada- 

 tion from a primordial type. Applying this principle to the 

 species of which he had given the history in his great work, he 

 believed himself able to reduce them to a very small number 

 of primitive stocks, of which he enumerates " fifteen." 



Lamarck,^ adverting to observed ranges of variation in 

 certain species, affirmed that such variations would proceed 

 and keep pace with the continued operation of the causes pro- 

 ducing them ; that such changes of form and structure would 

 induce corresponding changes in actions, and that a change of 

 actions, when habitual, became another cause of altered struc- 

 ture ; that the more frequent employment of certain parts 

 or organs leads to a proportional increase of development of 

 such parts ; and that as the increased exercise of one part is 

 usually accompanied by a corresponding disuse of another 

 part, this very disuse, by inducing a proportional degree of 

 atrophy, becomes another element in the progressive mutation 

 of organic forms. 



A third theorist§ calls to mind the instances of sudden 

 departure from the specific type, manifested by a malformed 

 or monstrous offspring, and quotes the instances in which 

 such malformations have lived and propagated the deviating 

 structure. He notes also the extreme degrees of change and 



* Heterogenic, 8vo, 1859. 



f Histoire Naturellc, Degeneration des Aniniaux, torn, iv., p. 311. 



J Philosophic Zoologique, 8vo, 1809, torn, i., ehs. 3 and 7. 



§ "Vestiges of the Natural History of Creation." 



