Robertson, Further Explanatory Remarks Concerning etc. 29 



lich heftige Kampfe mit den zahlreichen laevinodis-Kolonieu unseres 

 Gartens zu bestehen ; sie trugen dabei wiederholt Brut der letzteren 

 (auch Puppen) in ihv Nest. Im nachsten Jahre sah ich unter 

 den r ubida auch einige Exemplare der viel kleineren laevinodis aus 

 den Eingangslochern des Nestes kommen. Es ware wiinschbar, 

 die Sache experimentell nachzupriifen. 



Further Explanatory Remarks Concerning the Normal 

 Rate of Growth of an Individual and its Biochemical 



Significance. 



By T. Brail sford Robertson. 



(From the Rudolph Spreckels Physiological Laboratory of the University of California.) 



In a recent article 1 ) Moeser has called in question the cor- 

 rectness of my representation 2 ) of the autocatalytic character of 

 the growth-process. The chief objections which he raises are the 

 following : 



A. According to my formula the maximum velocity of growth 

 (= yearly, daily or hourly increment) occurs in the middle of the 

 growth-cycle. Moeser points out that this is, in actual experience, 

 frequently not the case. 



B. My formula, according to Moeser, represents growth purely 

 as a function of time. He points out that it is also a function of 

 temperature, light, moisture etc. Since these factors are not without 

 effect upon growth, therefore, Moeser argues, it is not correct to 

 speak of growth as a simple autocatalytic process. 



I will deal with these objections separately: 



A. As examples of the fact that the maximum rate of growth 

 frequently does not occur in the middle of a cycle, Moeser cites 

 measurements made by Sachs of the daily increment in the length 

 of a root of Vicia faba, of the elongation of three internodes of 

 Dahlia variabilis and of the elongation of four internodes of Fri- 

 tillaria imperialis. 



In this connection it appears necessary to point out: 



a) that increments of length are very unsafe measures of 

 increment in mass, since the diameter of the body measured may 

 alter as well as the length, and, moreover, even if the diameter 

 remains constant, the specific gravity of the substance composing 

 the body measured may also alter from time to time. Now chemical 

 reaction-formulae deal solely with the relation of mass to time or 



1) W. Moeser. Biolog. CentralbL, Bd. XXXII (1912), p. 365. 



2) T. Brailsford Robertson. Arch. f. Entwicklungsmech., Bd. XXV (1908), 

 p. 581, Bd. XXVI (1908), p. 108. Biolog. CentralbL, Bd. XXX (1910), p. 316. 



