HEREDITY FROM PHYSICO-CHEMICAL POINT OF VIEW. 77 



peculiarities of such deposits, and hence the specific morpholog- 

 ical characteristics of the cell, would be determined by the specific 

 chemical characteristics of the constituent proteins, in a manner 

 analogous to that by which the special form of a haemoglobin 

 crystal-aggregate is determined. And the special character of 

 the structure thus laid down would determine the special char- 

 acter of the metabolism, and hence the special type of physiolog- 

 ical activity exhibited by the cell. This last conclusion seems 

 inevitable, since the source of this activity is metabolism, which 

 in all living systems is under the control of structure. In other 

 words, the formation of a specific structure in the protoplasmic 

 substratum will necessitate a correspondingly specific type of 

 metabolism, since the nature and rate of the metabolic chemical 

 reactions are controlled by the structural conditions present; 

 the dependent physiological or functional manifestations must 

 therefore also be specific. 



We are thus led to conceive certain features of the organic form- 

 ative process in a somewhat definite manner, which may be 

 summarized briefly as follows: The specific characters of any 

 animal or plant are determined ultimately by the specific char- 

 acters of its structure-forming proteins. The developing germ 

 or the growing organism synthesizes specific proteins, and these, 

 since they determine the structural and hence the physiological 

 peculiarities of the organism, form the basis of its special char- 

 acter as an organic species. Accordingly one of our most funda- 

 mental problems is to determine why the cell builds up proteins 

 of its own specific type. The essential problems of heredity and 

 reproduction center here. As we have seen, heredity is exem- 

 plified whenever one yeast-cell or bacterium gives rise to another; 

 also whenever any cell grows and increases its living organized 

 material. This increase in living material is indispensable for 

 the continuance of the species, and for this reason we may charac- 

 terize growth as the fundamental life-process, and the problem of 

 growth in its most general aspect as identical with the problem 

 of heredity. The factors of growth are the factors of heredity. 



Aufsatze, Heft 5, 1908. Chodat made a similar suggestion for plant growth in 

 1905 (cf. D'Arcy Thompson: " Growth and Form," Cambridge Univ. Press, 1917, 

 p. 



