288 C. M. CHILD. 



has imputed to me certain views which I have not only never 

 held, but which I have expressly repudiated more than once. 

 And recently, in a brief reference to my work, Morgan ('07, pp. 

 3734) has cited certain conclusions as mine, which are very dif- 

 ferent from those which I have reached. I have considered 

 Driesch's criticisms elsewhere (Child, '07) and shall refer to these 

 and other criticisms only incidentally. But a brief statement of 

 my position with regard to certain features of the problems of 

 form and regulation and with especial reference to mechanical 

 factors, movement and use of parts and function in general seems 

 desirable in connection with the new facts presented above. 



i. Tlic Relation between Function and Form. 1 



In a fully developed organ certain processes occur which are 

 concerned with the maintenance of the organism as a whole. 

 These processes may affect either the relations of parts to each 

 other or the relations of the organism as a whole to the external 

 world, or both. They are commonly designated as functions, 

 i. e., the adult organism may be regarded as a complex machine, 

 which works or functions in a characteristic manner. 



But the functions characteristic of the adult organs do not 

 appear in development until a certain stage is reached and the 

 organ possesses a certain structure. Apparently then, develop- 

 ment up to the stage where function in the above sense begins is 

 a process of machine-building. Roux's distinction between a 

 formative and a functional stage in development expresses this 

 idea. 



But how is the machine constructed and what is the agency 

 which constructs it ? The material of which the machine is to be 

 made must be acted upon, arranged, transformed, localized, dif- 

 ferentiated, etc. Evidently this point of view necessitates the 

 assumption of a special formative agent or agents of some kind. 

 How shall we conceive this formative agent ? Pangenes, deter- 

 minants, formative substances, entelechies are some of the answers 

 which have been given to this question. All these answers are 

 much alike in that they regard the construction of the organism 

 as a process analogous in some sense to the construction of a 



1 Cf. Child, '06^, p. 402, '07. 



