466 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



shown that the basis of the entire community, the most 

 specialized form, the original fertile soldier, acquired 

 his characters in the usual way, by use, and that all 

 other forms have been derived from him by inheritance 

 modified by disuse, or degeneracy, under the influence 

 of variations in the food supply. 



This reply to Mr. Ball's argument was made by 

 me at a meeting of the Philadelphia Academy of Nat- 

 ural Sciences on May 23, 1893. In the latter part of 

 the same year an almost identical answer was pub- 

 lished by Herbert Spencer. My remarks were not pub- 

 lished until the end of the year. 



Mr. A. R. Wallace 1 presents the fact of change of 

 character under external stimulus as evidence of the 

 non-inheritance of acquired characters. Thus he cites 

 the cases of change of species of Artemia, in conse- 

 quence of increased salinity of water (antea, p. 229) ; 

 and of the change of color of a Texan Saturnia, when 

 its normal food-plant Juglans nigra was replaced by 

 J. regia. Under the new conditions the old characters 

 were not continued. In the same way the appearance 

 of all new characters might be assumed to prove non- 

 inheritance of the old ones. The obvious interpretation 

 of these facts is the one generally given them ; that, is, 

 they demonstrate the superior potency of certain new 

 stimuli over the inherited type of growth- energy. They 

 demonstrate that the energy of inheritance is not un- 

 changeable in its type, which is the condition of the 

 possibility of evolution. They do not demonstrate 

 that acquired characters cannot be inherited. 



Objections have been made to the supposition that 

 the simian characters of the lower human races are 

 due to inheritance because it has been shown that 



l-Xaturs, 1893, p. 267. 



