OUR FUTURE COURSE 215 



to the possibility of continued evolution of a char- 

 acter and to the complexity of interactions involved 

 in its production and maintenance, and the more 

 complex these interactions, the less chance there 

 is that the loss of any single factor may completely 

 eliminate the character. 



This idea may seem to involve a contradiction 

 in that I have spoken of the character as the result 

 of a certain heritage responding to a certain en- 

 vironmental stimulus. It may be quite true that 

 the character would never have been expressed 

 without the intervention of the external stimulus, 

 but in this as in the development of every organic 

 structure, relationships in the internal environ- 

 ment are involved. No character is a simple result 

 of one or a few genes responding to an environ- 

 mental stimulus of slight complexity; instead the 

 somatic expression of any heritage involves many 

 factors, activated sometimes by external stimuli 

 but always including complex interactions among 

 themselves as components of the internal environ- 

 ment. 



The importance of new conditions and changing 

 relations in the body can scarcely be overestimated 

 as an evolutionary force, and examples of their 

 action are common among living things. For 

 instance, the fishes have pharyngeal pouches which 

 are of the utmost importance in the development 

 of their respiratory system, and man retains these 



