38 The Science of Life. 



obtained. To attain such results, the palingenetic and 

 the kainogenetic phenomena must be sifted apart an 

 operation that requires more than one critical granum 

 salts. On what ground shall this critique be based? 

 Assuredly not by way of a circulus vitiosus on the onto- 

 geny again; for if kainogenetic characters are present 

 in one case, who will guarantee that a second case, 

 used for a comparison with the first, does not likewise 

 appear in a kainogenetic disguise? If it be once 

 admitted that not everything in development is palin- 

 genetic, that not every ontogenetic fact can be accepted, 

 so to speak, on its face value, it follows that nothing 

 in ontogeny is immediately available for the critique of 

 embryological development. This conclusion cannot 

 be escaped. The necessary critique must be drawn 

 from another source " namely, the results of compara- 

 tive anatomy. 



In some cases, however, the embryological verdict 

 is clear and unambiguous, and there can be little doubt 

 that the whole embryological story will become signifi- 

 cant, and reliably so, when the progress of physiological 

 embryology has made it possible to give a real and not 

 a fanciful content to the terms palingenetic and kaino- 

 genetic. 



It is difficult to find a proper term for the distinctively 

 modern movement which inquires into the nature of 

 Physiological growth- conditions. The Germans, among 

 Morphology, whom it originated and has made most 

 headway, call it Entiioicklungsmechanik or develop- 

 mental mechanics (in Kant's sense), but we are at 

 present a far cry from any vital mechanics in the Eng- 

 lish sense. Perhaps, therefore, the term physiological 

 morphology is preferable. 



Dr. Wilhelm Roux, who has the credit of setting this 

 new department of science upon its feet, defines "de- 

 velopmental mechanics", or "causal morphology", as 

 " the doctrine of the causes of organic forms, and hence 

 the doctrine of the causes of the origin, maintenance, 

 and degeneration of these forms ". 



One of the earliest exponents of this point of view 

 was Prof. W. His, whose thoughtful work Unsere Kor- 



