320 TIIK BEGINNINGS OF CAUSAL MORPHOLOGY 



simply the general properties or functions of organised 

 matter. 



Expressing Roux's thought in another way, we might say 

 that life can only be defined functionally, i.e., by an enumera- 

 tion of the "complex components " or elementary functions 

 which all living beings manifest, even down to the very simplest. 

 "Living beings," writes Roux, "can at present be defined 

 with any approach to completeness only functionally, that is 

 to say, through characterisation of their activities, for we 

 have an adequate acquaintance with their functions in 

 a general way, though our knowledge of particulars is by 

 no means complete" (p. 105, 1905). Defined in the most 

 general and abstract way, living things are material objects 

 which persist in spite of their metabolism, and, by reason of 

 their power of self-regulation, in spite also of the changes of 

 the environment. This is the " functional minimum-definition 

 of life "(pp. 106-7, 1905). 



We may now go on to consider the relation of function 

 to form throughout the course of development. Roux 

 distinguishes in all development two periods, in the first of 

 which the organ is formed prior to and independent of its 

 function, while in the second the differentiation and growth 

 of the organ are dependent on its functioning. Latterly 

 (1906 and 1910) Roux has distinguished three periods, 

 counting as the second the transition period when form is 

 partly self-determined, partly determined by functioning. 

 As this conception of Roux's is of the greatest importance 

 we shall follow it out in some detail. 



The idea was first elaborated in the Kainpf dcr Tlicilc 

 ( 1 88 1 ), where he wrote: "There must be distinguished in 

 the life of all the parts two periods, an embryonic in the 

 broad sense, during which the parts develop, differentiate 

 and grow of themselves, and a period of completer develop- 

 ment, during which growth, and in many cases also the 

 balance of assimilation over dissimilation, can come about 

 only under the influence of stimuli" (p. 180). There is thus 

 a period of self-differentiation in which the organs are 

 roughly formed in anticipation of functioning, and a period 

 of functional development in which the organs are perfected 

 through functioning and only through functioning. The two 



