LUDWIG AND MODERN PHYSIOLOGY. 379 



although by the observation of the successive stages iu the ontogenetic 

 process one may arrive at a perfect knowledge of the relation of these 

 stages to each other, this leaves the efficient causes of the development 

 unexplained (fiihrt nicht zu einem Erkenntniss ihrer bewirkenden 

 Ursachen). It does not teach us why one form springs out of another. 

 This brings him at once face to face with a momentous question. He 

 has to encounter three possibilities. He may either join the camp of the 

 biological agnostics and say with Du Bois Eeymond "ignoramus et 

 ignorabimus," or be content to work on in the hope that the physical 

 laws that underlie and explain organic evolution may sooner or later 

 be discovered, or he may seek for some hitherto hidden law of organism 

 of which the known facts of ontogenesis are the expression, and which, 

 if accepted as a law of nature, would explain everything. Of the three 

 alternatives Driesch prefers the last, which is equivalent to declaring 

 himself an out-and-out vitalist. He trusts by means of his experi- 

 mental investigations of the mechanics of evolution to arrive at " ele- 

 mentary conceptions" on which by "mathematical deduction" 1 a 

 complete theory of evolution may be founded. 



If this anticipation could be realized, if we could construct with the 

 aid of those new principia the ontogeny of a single living being, the ques- 

 tion whether such a result was or was not inconsistent with the uni- 

 formity of nature would sink into insignificance as compared with the 

 splendor of such a discovery. 



But will such a discovery ever be made? It seems to me even more 

 improbable than that of a physical theory of organic evolution. It is 

 satisfactory to reflect that the opinion we may be led to entertain on 

 this theoretical question need not affect our estimate of the value of 

 Dr. Driesch's fruitful experimental researches. 



1 "Elementarvorstellungen . . . die zwar rnatbematiscke Deduktion aller 

 Ersckeinungen aus sick gestatten mochten." Driesck. Beitriige zur tkeoretiscken 

 Morpkologie. Biol. Centralblatt, Vol. XII, p. 539, 1892. 



