42 PROGRESS OF SCIENCE IN THE CENTURY. 



community to the minimum number necessary to 

 avoid extinction say to a fertile queen with two 

 or three workers to look after her there seems no 

 reason to doubt that in a short time the whole ant- 

 hill would contain a population as effective as before. 

 Their powers are implied in their brain-inheritance ; 

 their capabilities of effective response to their en- 

 vironment have little or no external registration. 



It is possible that in some animals, where a social 

 life is sustained generation after generation, there 

 may be something corresponding to tradition which 

 gradually grows larger in its content, which forms 

 what may be called an external heritage as contrasted 

 with a natural or organic inheritance. 



It is also to be noted that some of the higher ani- 

 mals seem to have words particular sounds in- 

 dicative of certain things or expressive of definite 

 emotional states and it can hardly be doubted that 

 the existence of these will facilitate mental processes. 

 In some cases, too, the permanent products which 

 animals make dwellings, nests, roads, and the like 

 may become suggestive symbols, and may be of 

 some importance as stimuli to successive genera- 

 tions. 



Yet after all these admissions are made, it re- 

 mains as a great contrast between man and animals 

 that our possession of language and methods of re- 

 cording conclusions makes the progress of science 

 possible. In the case of ants it seems as if the brain 

 had evolved in the direction of a more and more per- 

 fect automaton ; in the case of man, the existence of 

 external means of registration has made it possible 

 for the brain to be born more and more plastic, less 

 weighted by an inheritance of ready-made powers, in 

 a word, more educable. " To the educable animal 



