August 31, 1917] 



SCIENCE 



203 



iu the individual, but in the race, and are 

 called adaptations. Adaptations are means 

 of avoiding the effects of limiting factors. 



Another means of integration is seen in 

 biotic succession. Here the integration ex- 

 tends over a considerable period of time 

 and its benefits do not accrue to the individ- 

 ual or the race, but to succeeding genera- 

 tions and different species. The integra- 

 tive effect in succession may be largely pro- 

 duced by the death and decay of an asso- 

 ciation resulting in the accumulation of 

 humus. Thus both xerophytic and hydro- 

 phytic plants prepare the way for a meso- 

 phytic flora. The limiting factor here is 

 water, which is too scarce in the one case 

 and too abundant in the other. By the ac- 

 cumulation of humus, the properties of the 

 soil are so altered that a more favorable 

 water supply is offered to later generations, 

 and in this way the eft'ect of the limiting 

 factor is counteracted. 



All these processes which bring about 

 integration between the relations of living 

 organisms to the factors of the environment 

 that determine their growth and activity 

 are evidently based on a single fundamental 

 principle, to which Professor L. J. Hen- 

 derson has applied the appropriate mis- 

 nomer teleology.^' Wlierever integration 

 is found in the factors influencing the indi- 

 vidual, the race or the association, it is pos- 

 sible to deflne a closed system. Such a sys- 

 tem includes all the factors which can be 

 integrated, that is, all the possible limiting 

 factors for any given process. These sys- 

 tems may focus about a single cell, an 

 organ, an organism or a group of organ- 

 isms. They are inclusive. The life of a 

 plant, for example, is determined by a 

 complex of factors between which integra- 

 tion is found to occur. At the same time 

 the functional activity of the root system 

 is determined by another complex of inte- 

 grated factors, and the functional activity 



13 The order of nature, 1917. 



of the leaves by still a different set. Since 

 the life of the root system is dependent on 

 the products of the activity of the leaves, 

 these represent members of the complex 

 which conditions the growth and function 

 of the root system. Such internal factors 

 as enter into the complex of factors cen- 

 tering about the life of a portion of an or- 

 ganism are likewise subject to integration. 

 In this way the condition of the root sys- 

 tem affects the leaves and the condition of 

 the leaves affects the root system. Correla- 

 tions are therefore manifestations of the 

 principle of integration. 



The organic world can be analyzed into 

 systems of various orders, those of a higher 

 order being inclusive of, or divisible into, 

 systems of a lower order. These systems 

 are invariably overcoming the effects of 

 limiting factors. The limiting factor is the 

 stimulus to which the system reacts. The 

 reaction places the organism in a more effi- 

 cient relation with its environment, but no 

 matter how many reactions are carried out, 

 there is always some limiting factor left, 

 and so the organism is kept constantly 

 busy. The end result is to approximate 

 more or less closely some kind of average 

 of all the resources at its disposal. 



I think it might be possible to go even 

 further and get a quantitative measure of 

 the degree to which the process of integra- 

 tion has been carried, by considering the 

 number of factors integrated and how close 

 an approximation to the normal curve of 

 error had been obtained. Such a quantita- 

 tive measure would likewise be an index of 

 the stage of evolution that an organism had 

 reached." At the verj' least, the Law of 

 the Minimum or the principle of limiting 

 factors offers a sound basis from which such 

 intangible processes as behavior, correla- 



i'' Our criterion of ' ' degeneracy " in a living or- 

 ganism i3 based essentially on a decrease in the 

 number or range of factors between which inte- 

 gration is possible. 



