No. 610] GENETICS VERSUS PALEONTOLOGY 635 



which they record or infer. In that direction lies oppor- 

 tunity for consultation with the men who study enzymes, 

 chromosomes, heredity and variation. 



The Batesonian hypothesis that both the progressive 

 differential emphases or suppressions of organs, and the 

 focal outgrowth of new structures, have been due to a 

 secular, differential stopping down of inhibitory factors 

 inherent in the germ-cells seems to the present writer 

 quite consistent with the observed facts of evolutionary 

 change ; but apparently no obsen^ations that the paleon- 

 tologist can make could furnish any critical tests of this 

 hypothesis ; it therefore has for him a stimulative philo- 

 sophical value, but hardly constitutes a working hypothe- 

 sis for the discovery of new facts and principles in his 

 limited field. 



The nature of later events being determined in part by 

 the nature of their precedent events, no matter how many 

 causal series may be interwoven in the final outcome, it 

 follows that paleontologists, like other historians, con- 

 tribute to a partial understanding of existing conditions 

 merely by arranging past events in their true chronolog- 

 ical sequence. The characteristics of existing Cetacea are 

 determined in part by the germinal and somatic charac- 

 teristics of their remote quadrupedal ancestors, as well 

 as by the conditions of the pelagic life into which they 

 somehow drifted; so too the characteristics of man, as a 

 bipedal, bimanous, anthropoid Primate are determined in 

 part, as I believe, by the fact that the remote ancestors 

 of the man-greatape stock were arboreal, quadrumanous, 

 lemuroid Primates of the Lower Eocene. 



For such reasons, I must continue to hold that "pro- 

 gressive adaptation" when cleared of all implications as 

 to the mode of evolution, stands for a historical and 

 verifiable process; that the time for developing phylo- 

 genetic conclusions and for revising comparative anat- 

 omy and classification is always now, as fast as the evi- 

 dence can be gathered and analyzed. 



