lotka: efficiency in organic evolution 399 



Instead of this he acts in accordance with the sUghtly erron- 

 eous curve y' , and hence consumes 



x' = OP' (25) 



so that we may write 



5 X = x' - X = OP' - OP = PP' (26) 



This, because he makes an error in 



y = vE -^ v'E' (22) 



making it y' = {v + be) E + v'E' (23) 



so that y' - y =- E 8e = PQ (27) 



8e=^ (28) 



^ = l^E = -e/^ (29) 



de PQ / dx 



Substituting in (21) we have: 



■^ = -^E — {vE + v'E') (30) 



de bx / dx 



= -vE/— {vE + v'E') (31) 



/ dx 



which is the desired expression for the differential coefficient 



^7* 



— for the case that e denotes an error of valuation 



limitations of the method here developed 



In conclusion the writer wishes to consider the limitations of 

 the method presented above and to point out their significance 

 and to indicate at what points there is room for further devel- 

 opment. 



1. We have restricted our attentions to routine or habitual 

 activities, in particular to such as have a definite economic 

 significance. 



On reflection it is found that this restriction in practise is 

 ahnost no restriction at all, that only a vanishingly small pro- 



