6o6 ON INCREASE IN COMPLEXITY [pt. m 



tion and in embryonic development", says Child, "results from the 

 establishment in one way or another of some region or portion of 

 this protoplasmic reaction-system as a region of higher rate of 

 dynamic activity. This region dominates development, becomes the 

 apical or head region and determines the axial gradient or gradients 

 which constitute the dynamic basis of polarity and of individuation." 



3-9. Organised and Unorganised Growth 



An idea which has much importance for the study of the inter- 

 relations between growth and differentiation was contained in a 

 paper by Faris on the pigmentation of Amblystoma embryos. The 

 details of his investigations into the ontogenesis of this pigment will 

 be referred to again in the section on pigments; here I am con- 

 cerned to refer to his distinction between "proliferation metabolism" 

 and "differentiation metabolism". He observed that, during the 

 development of the myotomes of Amblystoma embryos, the pigment 

 accumulated in the cells proportionally to differentiation and not to 

 growth. He therefore suggested that it could be regarded as an 

 index of the difference in nature between the type of metabolism 

 associated with growth and that associated with differentiation, ad- 

 mitting, of course, that the two processes were only completely 

 separable in the abstract. "Proliferation", according to Faris, "must 

 lack the wear-and-tear processes that are characteristic of differentia- 

 tion and for that reason it lacks the function of pigment production." 

 It must be admitted that these concepts are vague enough, and they 

 rest on an unsatisfactory, because unquantitative, basis. But they have 

 a real interest, in view of two lines of recent thought : firstly, the 

 distinction made by Murray between the groups of processes in 

 embryonic development according to velocity at different times, and 

 secondly, the numerous papers of Warburg and his school (see Section 

 4-20), which introduce into these problems the concepts of organised 

 and unorganised growth metabolism. These investigations will be 

 referred to in detail in the next section. If it should turn out that 

 Faris's conception of two types of metabolism found a quantitative 

 basis in the data of Warburg and his collaborators, an interesting 

 and quite important avenue would be open for further investigation. 



The notion of a distinction between organised and unorganised 

 growth had not, however, its sole origin in Germany, for Byerly 

 had also come to it from very different ground. Setting out 



