412 



ON INCREASE IN SIZE 



[PT. Ill 



growth were simply expressions of a more or less rapid return to 

 the chemical equilibrium between nucleus and cytoplasm which had 

 been temporarily shifted through the process of fertilisation. He 

 thought that there occurred in the sea-urchin's egg during the early 

 stages of its development a great synthesis of nuclear material, and 

 that this synthesis progressed, roughly speaking, all the more rapidly 

 the more nuclein was formed. The velocity of nuclear synthesis, said 

 Loeb, increases with lapse of time in geometrical progression. 

 Further, various observers, using the Q^k, formula, had concluded 

 that the growth-process had a "chemical temperature coefficient", 

 so Robertson felt fully justified in speaking of a "master-reaction" 

 of growth, and in thinking of it as autocatalytic — a reaction, which, 

 because it would be slower than any other, would act as the limiting 

 factor of growth, and would impress its own particular character 

 on the general appearance of the whole process from outside. 



Table 54. Larval growth of frog [tadpole). 



* "Obviously another growth-cycle supervening", said Robertson 



In his later writings, Robertson added further demonstrations of 

 the applicability of the autocatalysis equation to growth, but he also 

 added a large amount of extremely speculative considerations, such 

 as the "nutrient level", the "endogenous catalyser", etc., into which 

 we cannot here enter. Some of his suggestions, for example that the 

 autocatalyst is lecithin, may be regarded as now definitely out of 

 court. He showed, however, that the pre-natal growth in man (using 

 Zangemeister's figures) was susceptible of description in an auto- 

 catalytic curve with its early " autokinetic " phase (Robertson's 

 terminology), and its late "autostatic" phase. He also used, for the 



