388 LAMARCK, HIS LIFE AND WORK 
tological papers. Hyatt’s views on acceleration were 
adopted by Neumayr.* Waagen,t 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.’’ ¢ 
While the paleontological facts afford complete 
and abundant proofs 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. 
+ Palzontologica Indica. Jurassic Fauna of Kutch. I. Cephalopoda, 
pp. 242-243. (See Hyatt’s Genesis of the Arietide, pp. 27, 42.) 
t‘*Genera of Fossil Cephalopods,” Proc. Bost. Soc. Nat. Hist., 
xxli., April 4, 1883, p. 265. 
§‘‘ Revision of the North American Porifere.” Memoirs Bost. 
Soc, Nat. Hist., 'ii:,, partiiv., 0877. 
