September 24, 1909] 



SCIENCE 



391 



natural selection or survival of the fittest 

 would suiBce to account for the evolution 

 of the ever-increasing complexity of living 

 beings which has occurred in the later his- 

 tory of this globe. The adaptations, i. e., 

 the reactions of the primitive organism to 

 changes in its environment, must become 

 continually more complex, for only by 

 means of increasing variety of reaction 

 can the stability of the system be secured 

 within greater and greater range of ex- 

 ternal conditions. The difference between 

 higher and lower forms is therefore merely 

 one of complexity of reaction. 



The naked protoplasm of the Plasmo- 

 dium of Myxomycetes, if placed upon a 

 piece of wet blotting-paper, will crawl 

 towards an infusion of dead leaves, or 

 away from a solution of quinine. It is the 

 same process of adaptation, the deciding 

 factor in the struggle for existence, which 

 impels the greatest thinkers of our times 

 to spend long years of toil in the invention 

 of the means for the offense and defense 

 of their community or for the protection 

 of mankind against disease and death. 

 The same law which determines the down- 

 ward growth of the root in plants is re- 

 sponsible for the existence to-day of all the 

 sciences of which mankind is proud. 



The difference between higher and lower 

 forms is thus not so much qualitative as 

 quantitative. In every case, whatever part 

 of the living world we take as an example, 

 we find the same apparent perfection of 

 adaptation. Whereas, however, in the 

 lower forms the adaptation is within 

 strictly defined limits, with rise in type the 

 range of adaptation steadily increases. 

 Especially is this marked if we take those 

 groups which stand, so to speak, at the 

 head of their class. It is therefore im- 

 portant to try and find out by a study of 

 various forms the physiological mechanism 

 or mechanisms which determine the in- 



creased range of adaptation. By thus 

 studying the physiological factors, which 

 may have made for success in the struggle 

 for dominance among the various repre- 

 sentatives of the living world, we may ob- 

 tain an insight into the factors which will 

 make for success in the further evolution 

 that our race is destined to undergo. 



It is possible that, even at this time, ob- 

 jections may be raised to the application to 

 man of conclusions derived from a study 

 of animals lower in the scale. It has in- 

 deed been urged, on various grounds, that 

 man is to be regarded as exempt from the 

 natural laws which apply to all the other 

 living beings. "When we inquire into the 

 grounds for assuming this anomic, this 

 outlawed condition of man, we generally 

 meet with the argument that man creates 

 his own environment and can not therefore 

 be considered to be in any way a product 

 of it. This modification or creation of en- 

 vironment is, however, but one of the 

 means of adaptation employed by man in 

 common with the whole living kingdom. 

 From the first appearance of life on the 

 globe we find that one of the methods 

 adopted by organisms for their self-preser- 

 vation is the production of some artificial 

 surroundings which protect them from the 

 buffeting of environmental change. What 

 is the mucilaginous envelope produced by 

 microorganisms in presence of an irritant, 

 or the cuticle or shell secreted by the out- 

 ermost cells of an animal, but the creation 

 of such an environment? All unicellular 

 organisms, as well as the units composing 

 the lowest metazoa, are exposed to and 

 have to resist every change in concentra- 

 tion and composition of the surrounding 

 water. When, however, a body cavity or 

 ccBlom, filled probably at first with sea- 

 water, made its appearance, all the inner 

 cells of the organism were withdrawn from 

 the disturbing influence of variations in 



