308 



POPULATIONS 



2000 



ASYMPT0IE^750_^_^^ 



o 



Fig. 



DAYS 



99. The logistic growth of two laboratory populations of the flour beetle, Tribo- 



lium confusum; one in 64 gm. of flour (upper curve), and one in 16 gm. (lower curve). (From 

 Gause. ) 



(f) 



400 - 



< 



9 



> 300 



U. 200 

 O 



a: 



LU 



QQ 100 



10 



14 



2 4-68 



DAYS 

 Fig. 100. The logistic growth of three laboratory populations of the water flea, Moina mac- 

 rocopa, at three temperatures. ( From Terao and Tanaka. ) 



Certain conclusions can be drawn from 

 examination of these five logistic curves. 



In the first place, as already noted, the 

 general shape of a population growth figure 

 is sigmoid and symmetrical. 



Secondly, the correspondence between 

 the theoretical curves and the actual obser- 

 vations, loosely, the "goodness of fit," de- 

 serves some comment. We can assume that 

 the curves are fitted with skill, i.e., that the 

 best possible agreement between the data 



and the function is represented.* While 

 this certainly is not true in every reported 

 instance, it seems, for reasons of discussion, 



• At the risk of seeming captious, the point 

 might be made that any published curve 

 would, of necessity, be a moderately good fit, 

 since an author would be loth to present one 

 not adequate. Were this true to any extent, 

 there would exist in the literature a bias in 

 favor of the curve rather than the facts. We do 

 not take this criticism too seriously. 



