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THE AMEBIC AX NATURALIST [Vol. LII 



an environmental complex. This is a healthy sign as it 

 will greatly assist in the correlation of field and labora- 

 tory studies. Recently Livingston ('17, p. 8) has said: 



speakof a single condition asking a cause of an observed effect. The 

 next generation of physiologists will have to learn to handle more than 

 a single variable and to deal with complexes of conditions. 7 



This recalls John Stuart Mill's statement that : 



that this invariable M-<|.ini.-.. subsists. It is usually between a .-onso- 

 quent and the sum of several antecedents; the concurrence of all of them 

 being requisite to produce, that is, to be certain of being followed by 

 the consequent. In such cases it is very common to single out one only 

 of the antecedents under the denomination of cause, calling the others 



merely Conditions The real cause is the whole of these antecedents; 



and we have, philosophically speaking, no right to give the name of 

 cause to one of them, exclusively of the others. ... All the conditions 

 are equally indispensable to the production of the consequent; and the 



introduce them all. ? ^ P 



When Hooker ('17, p. 201) states that, "It is neces- 

 sary to get away from the custom of discussing causes, 

 however difficult this may be. The idea of causation in- 

 variably indicates incomplete analysis," he does not ex- 

 press the full significance of Livingston's remark. We 

 have not yet outgrown Mill's statement. 



In addition to its application to the individual animal, 

 Bancroft's law applies w T ith equal force to the dynamic 

 tendencies of plant and animal associations. The domi- 

 nance of a climax society shows that (Adams, '08, p. 125) : 



Such dominance, in general, implies extensive range, relative abund- 

 ance, and ability to indefinitely succeed or perpetuate itself under given 

 conditions. ... The primary environmental conditions tend to encroach 

 upon all others. The local conditions thus tend to become transformed in 

 the direction of the dominant environment and to be appropriated by it. 



The associations . . . are thus given a definite dynamic trend Minor 



environments tend to become encroached upon by the dominant regional 

 influences and ultimately to become extinct. The succession of socie- 



