3oo POPULAR SCIENCE MONTHLY. 



of possible actions small, but they cover also a small period of time. 

 In animals which have acquired a higher organization the adjustments 

 are more complex, both because the reactions are more varied and 

 because they cover a longer period of time. Thus the jelly fish depends 

 upon such food as happens to come within its reach, seizing from 

 moment to moment that which it encounters ; but a lobster pursues its 

 food, making complicated movements in order to reach and seize it. 

 One can trap lobsters easily ; I doubt if one could trap a jelly fish at all. 

 The next great advance is marked by the establishment of communica- 

 tion between individuals of the same species. About this phenomenon 

 we know exceedingly little; the investigation of it is one of the most 

 important duties of the comparative physiologist. Its bionomic value 

 is obviously great, for it allows an individual to utilize the experience 

 of another as well as its own. We might, indeed, compare it with the 

 addition of a new sense, so greatly does it extend the sources of infor- 

 mation. The communication between individuals is especially charac- 

 teristic of vertebrates, and in the higher members of that subkingdom 

 it plays a very great role in aiding the work of consciousness. In man, 

 owing to articulate speech, the factor of communication has acquired 

 a maximum importance. The value of language, our principal medium 

 of communication, lies in its aiding the adjustment of the individual 

 and the race to external reality. Human evolution is the continuation 

 of animal evolution, and in both the dominant factor has been the 

 increase of the resources available for consciousness. 



In practical life it is convenient to distinguish the works of nature 

 from the works of man, the 'natural' from the 'artificial.' The biol- 

 ogist, on the contrary, must never allow himself to forget that man is 

 a part of nature and that all his works are natural works. This is spe- 

 cially important for the present discussion, for otherwise we are likely 

 to forget also that man is as completely subject to the necessity of 

 adjustment to external reality as any other organism. From the bio- 

 logical standpoint all the work of agriculture, of manufactures, of com- 

 merce and of government is a part of the work of consciousness to 

 secure the needed adjustments. All science belongs in the same cate- 

 gory as the teleological efforts of a jelly fish or a lobster. It is work 

 done at the command of consciousness to satisfy the needs of existence. 

 The lesson of all this to us is that we should accustom ourselves to 

 profit by our understanding of the trend of evolution, which, in the 

 progress humanity makes, obeys the same law of adaptation to objective 

 reality which has controlled the history of animals. This view of the 

 conditions of our existence puts science in its right place. As all sen- 

 sations are symbols of external reality useful to guide organisms to 

 teleological reactions, so is all science symbolic and similarly useful. 



