388 



LAMARCK, HIS LIFE AND WORK 



tological papers. Hyatt's views on acceleration were 

 adopted by Neumayr.* Waagen,-]- from his studies 

 on the Jurassic cephalopods, concludes that the 

 factors in the evolution of these forms were changes 

 in external conditions, geographical isolation, com- 

 petition, and that the fundamental law was not that 

 of Darwin, but " the law of development." Hyatt 

 has also shown that at first evolution was rapid. 

 " The evolution is a purely mechanical problem in 

 which the action of the habitat is the working agent 

 of all the major changes; first acting upon the adult 

 stages, as a rule, and then through heredity upon 

 the earlier stages in successive generations." He 

 also shows that as the primitive forms migrated and 

 occupied new, before barren, areas, where they met 

 with new conditions, the organisms " changed their 

 habits and structures rapidly to accord with these 

 new conditions." X 



While the palaeontological facts afford complete 

 and abundantLjjroofs of the modifying action of 

 changes in the environment, Hyatt, in 1877, from his 

 studies on sponges,§ shows that the origin of their 

 endless forms " can only be explained by the action 

 of physical surroundings directly working upon the 

 organization and producing by such direct action 

 the modifications or common variations above de- 

 scribed." 



* Zeitschr. der deutsch. geol. Gesellschaft, 1875. 



f Palitontologica Indica. Jurassic Fauna of Kutch. I. Cephalopoda, 

 pp. 242-243. (See Hyatt's Genesis of Ihe Arietida, pp. 27, 42.) 



if "Genera of Fossil Cephalopods," Proc. Bost. Soc. Nat. Hist., 

 xxii., April 4, 1883, p. 265. 



§" Revision of the North American Poriferce." Memoirs Bost. 

 Soc. Nat. Hist., ii., partiv., 1877. 



