722 ALPHEUS HYATT. 



This law of acceleration was, after the publication of Cope's and also 

 of Hyatt's first paper (1870), arrived at independently by Wiirtenberger,* 

 and adopted by the distinguished German paleontologist Neurnayr, 

 though he, apparently in ignorance of Hyatt's much earlier results, gives 

 the credit for its discovery to Wiirtenberger, as does Weismann. 



These changes Professor Hyatt insisted were primarily due to changes 

 in the environment acting mechanically on the organism at different 

 ages, the Lamarckian factors of use and disuse as well as environmental 

 changes being constantly operative. 



To explain the facts of retardation or abbreviated metamorphosis Dr. 

 Hyatt formulates the law or process concerned in these phenomena, and 

 which explain the mechanism of gradation, whether progressive or retro- 

 gressive, as follows : — 



" Changes in environment, which introduce new adaptive characteristics 

 in the nealogic or adult stages, necessarily add these to the hereditary 

 stages of the younger periods of growth, and thus shorten the develop- 

 ment of the latter by direct development." He goes on to illustrate this 

 process by citing the changes of insects, of Taenia, and the loss of pro- 

 gressive characters correlated with a highly accelerated mode of develop- 

 ment in man, due to a change from a horizontal to an upright position, 

 and which, he says, were first pointed out nearly a century ago by 

 Lamarck. 



We will now, as briefly as the subject admits, trace the evolution of 

 Professor Hyatt's views on evolution. 



It has been objected to both Cope and Hyatt's theory that their law 

 or process of acceleration and retardation are merely statements of facts. 

 But both of these observers very soon after working out, each independ- 

 ently of the other, and in very different groups, these facts and processes, 

 arrived at the conclusion that the changes they formulated were primarily 

 due to the Lamarckian factors of change of environment, and to use and 

 disuse. 



They, with others of their contemporaries, rehabilitated and extended 

 the Lamarckian factors and became the founders of the Neolamarckian 

 school of evolutionists. 



Hyatt's first public avowal of evolutional views was in a paper read in 

 1870,f though for several years he had practically adopted the theory 



* Ausland, 1873. 



t On Reversions among the Ammonites. Proc. Boston Soc. Nat. Hist., XiV. 

 June, 1871. 



