ADAPTATION AND THE PEOBLEM OF '^OEGANIC 

 PURPOSEFULNESS." II 



DR. FRANCIS B. SUMNER 

 ScRiPPS Institution fob Biological Research, La Jolla, Cauf. 



IV. The Peinciple of Trial and Error in Relation to 

 Regulative Phenomena^ ^ 



Driesch and some other vitalists draw their most ef- 

 fective ammunition from the phenomena of experimental 

 embryology and regeneration. How is it that a frag- 

 ment of a developing organism— any fragment, within 

 certain limits— can produce the ^vhole! How it is that 

 various perversions of the normal course of development 

 do not prevent the attainment of the normal end ? How 

 is it that certain adult organs, e. g., the lens of the eye of 

 a triton, when removed by a highly "unnaturar' opera- 

 tion, is nevertheless restored, and restored by a process 

 quite different from that in which it is normally pro- 

 duced in embryonic development? 



At the outset we must make two admissions: (1) that 

 these processes can not be the result of a mechanism spe- 

 cificallx- a(l;i])tod in advance to meet these particular exi- 

 .aviicics, niid (l!) that they can not be satisfactorily 

 explained 1)\ assuming any preformation of the parts 

 which aiH' restored. The former supposition is to be re- 



I'The "trial and error" principle has of late years come into the fore- 

 ground of biological discussion, largely through the writings of .Jennings. 



Spencer {Vrxncivles of Psychology, Vol. 1, pp. 544^.-)45) to account for the 

 origin of adaptive responses to stimuli, and was later develop^nl by Bain. 



"Der Kampf der Theile im Organismus" '(1881). More recentlv, Baldwin 

 (Mental Pevciopw^if, 18£>8, Chapter VII; Btidniniunt end Fi 1902, 

 pp. 108-115) has further elaborated the same fuu.latmntnl i.lfa that of 



pyschologists (c.g:, Lloyd Morgan and Thorndiko) liav,- aUo lai.i >tiv- on 

 this principle. 



338 



