TENTH LECTURE. 



EVOLUTION AND EPIGENESIS. 



C. O. WHITMAN. 



" Die Physiologie ist keine Wissenschaft, wenn nicht durch die innige Verbindung mit der Phi- 

 losophie." — JoH. Muller, Physiologie d. Gesicktssinties, p. 36. 



It is well from time to time to take account of stock even in 

 such intangible things as theories may appear to be ; it is 

 only in this way that we can measure the progress made in 

 the interpretation of facts. Theory without fact is phantasy; 

 but fact without theory is chaos. Divorced, both are useless; 

 united, they are equally essential and fruitful. The father of 

 modern embryology, Karl Ernst von Baer, modestly described 

 his great work on "The Evolution of Animals" (1828) as 

 '^ Beobachtung und Reflexion" — Observation and Reflection; 

 and a similar motto adorns the title-page of Goethe's " Zur 

 Morphologic" (18 17). The words are : ^^ Erf aiming, BetracJit- 

 nng, Folgening'' — Experience, Reflexion, Inference. 



Fact-gathering and theory-making are both prime functions 

 of the investigator. Mutual service is the principle which ties 

 them together. This point was strongly put by Huxley in his 

 review of the cell-theory, in 1853 : 



" In so complex a science as that which relates to living 

 beings, accurate and diligent empirical observation, though 

 the best of things so far as it goes, will not take us very far, 

 and the mere accumulation of facts without generalization and 

 classification is as great an error intellectually as, hygienically, 

 would be the attempt to strengthen by accumulating nourish- 

 ment without due attention to the primal viae, the result in 

 each case being chiefly giddiness and confusion in the head." ^ 



^ British and Foreign Medico-Chirurgical Review, vol. XII, p. 291. 



