September 24, 1900] 



SCIENCE 



395 



enee is secured hy endowing the head cen- 

 ter with a power, firstly, of controlling and 

 abolishing the activities {i. e., all those 

 aroused by external stimuli) of all other 

 parts of the central nervous system, and, 

 secondly, of arousing these parts to a re- 

 action immediately determined by the im- 

 pression received from the projicient sense 

 organs of the head and originated by some 

 change in the surroundings of the animal 

 which has not yet affected the actual sur- 

 face of its body. 



Education bij Experience.— The factors 

 which so far determine success in the strug- 

 gle for predominance are, in the first 

 place, foresight and power to react to com- 

 ing events, and, in the second place, control 

 of the whole activities of the organism by 

 that part of the central nervous system 

 which presides over the reaction. The ani- 

 mal therefore profits most which can sub- 

 ordinate the impulses of the present to the 

 exigencies of the future. 



An organism thus endowed is still, how- 

 ever, in the range of its reactions, a long 

 way behind the type which has attained 

 dominance to-day. The machinery we have 

 described, when present in its simplest 

 form, sufiices for the carrying out of 

 reactions or adaptations which are deter- 

 mined immediately by sense impressions, 

 advantage being given to those reactions 

 which are initiated by afferent stimuli af- 

 fecting the projicient sense organs at the 

 head end of the animal. "With the forma- 

 tion of the vertebrate type, and probably 

 even before, a new faculty makes its ap- 

 pearance. Up to this point the reactions 

 of an animal have been what is termed 

 "fatal," not in the sense of bringing death 

 to the animal, but as inexorably fixed by 

 the structure of the nervous system in- 

 herited by the animal from its precursors. 

 Thus it is of advantage to a moth that it 

 should be attracted by, and fly towards 

 light objects— e. g., white flowers— and 



such a reactivity is a function of the struc^ 

 ture of its nervous system. When the 

 light object happens to be a candle flame 

 the same response takes place. The first 

 time that the moth flies into and through 

 the candle flame, it may only be scorched. 

 It does not, however, learn wisdom, but the 

 reaction is repeated so long as the moth caa 

 receive the light stimuli, so that the re- 

 sponse, which in the average of cases is for- 

 the good of the race, destroys the individ- 

 ual under an environment which is differ- 

 ent from that under which it was evolved. 

 There is in this case no possibility of edu- 

 cating the individual. The race has to be 

 educated to new conditions by the ruthless- 

 destruction of millions of individuals, until 

 only those survive and impress their stamps 

 on future generations whose machinery; 

 by the accumulation and selection of mi- 

 nute variations, has undergone sufScient 

 modifications to determine their automatic- 

 and "fatal" avoidance of the harmful! 

 stimulus. 



The next great step in the evolution of' 

 our race was the modification of the nerv-«. 

 ous system which should render possible 

 the education of the individual. The- 

 meehanism for this educability was sup- 

 plied by the addition, to the controlling 

 sensory ganglia of the head, of a mass of' 

 nervous matter which could act, so to 

 speak, as an accessory circuit to the various, 

 reflex paths already existing in the original 

 collection of nerve ganglia. This access 

 sory circuit, or upper brain, comes to act 

 as an organ of memory. Without it a chilcJ 

 might, like the moth, be attracted by a 

 candle flame and approach it with its hand. 

 The injuiy ensuing on contact with the 

 flame would inhibit the first movement and 

 cause, a drawing back of the hand. In the 

 simple reflex mechanism there is no reason 

 why the same series of events should not be 

 repeated indefinitely, as in the case of the 

 moth. The central nervous system, how- 



