•390 



SCIENCE 



[N. S. Vol. XXX. No. 769 



Adaptation.— In his study of living be- 

 ings, the physiologist has one guiding prin- 

 ■eiple which plays but little part in the 

 •sciences of the chemist and physicist, 

 namely, the principle of adaptation. Adap- 

 'tation or purposiveness is the leading 

 •characteristic of every one of the func- 

 tions to which we devote in our text-books 

 the chapters dealing with assimilation, res- 

 piration, movement, growth, reproduction, 

 and even death itself. Spencer has defined 

 Sife as "the continuous adjustment of in- 

 'ternal relations to external relations." 

 Every phase of activity in a living being 

 ■3S a sequence of some antecedent ehsinge 

 ■in its environment, and is so adapted to 

 ithis change as to tend to its neutralization 

 ■and so to the survival of the organism. 

 This is what is meant by adaptation. It 

 Tvill be seen that not only does it involve the 

 teleological conception that every normal 

 activity must be for the good of the organ- 

 ism, but also that it must apply to all the 

 relations of living beings. It must there- 

 fore be the guiding principle, not only in 

 physiology, with its special preoccupation 

 with the internal relations of the parts of 

 the organism, but also in the other branches 

 of biology, which treat of the relations of 

 the living animal to its environment and 

 ■of the factors which determine its survival 

 in the struggle for existence. Adaptation 

 therefore must be the deciding factor in 

 the origin of species and in the succession 

 «)f the different forms of life upon this 

 'earth. 



Origin of Life.— A living organism may 

 (be regarded as a highly unstable chemical 

 ■system which tends to increase itself con- 

 tinuously under the average conditions to 

 "which it is subject, but undergoes disin- 

 tegration as a result of any variation 

 from this average. The essential condi- 

 tion for the survival of the organism is 

 that any such disintegration shall result in 



so modifying the relation of the system to 

 the environment that it is once more re- 

 stored to the average in which assimilation 

 can be resumed. 



We may imagine that the first step in 

 the evolution of life was taken when, dur- 

 ing the chaotic chemical interchanges 

 which accompanied the cooling do'wn of the 

 molten surface of the earth, some com- 

 pound was formed, probably with absorp- 

 tion of heat, endowed with the property 

 of polymerization and of growth at the ex- 

 pense of surrounding material. Such a 

 substance could continue to grow only at 

 the expense of energy derived from the 

 surrounding medium, and would undergo 

 destruction with any stormy change in its 

 environment. Out of the many such com- 

 pounds which might have come into being, 

 only such would survive in which the 

 process of exothermic disintegration 

 tended towards a condition of greater sta- 

 bility, so that the process might come to 

 an end spontaneously and the organism or 

 compound be enabled to await the more 

 favorable conditions necessary for the 

 continuance of its growth. "With the con- 

 tinued cooling of the earth, the new pro- 

 duction of endothermic compounds would 

 probably become rarer and rarer. The be- 

 ginning of life, as we know it, was possibly 

 the formation of some complex, analogous 

 to the present chlorophyll corpuscles, with 

 the power of absorbing the newly pene- 

 trating sun's rays and of utilizing these 

 rays for the endothermic formation of 

 further unstable compounds. Once given 

 an unstable system such as we have imag- 

 ined, with two phases, viz., (1) a condition 

 of assimilation or gro'wth by the endother- 

 mic formation of new material; (2) a con- 

 dition of "exhaustion," in which the exo- 

 thermic destructive changes excited by 

 unfavorable external conditions came to an 

 end spontaneously— the great principle of 



