Environment and Variation 69 



more and more to confirm the conduct as habitual in those 

 who survive. 



Obviously a variation of habit is often accompanied by 

 a variation of physical formation, a variant of habit o,r 

 conduct may precede and cause a corresponding variant of 

 form, or it may follow as a consequence of such a change. 

 For example, a species of fowl finding a new environment, 

 safer and with more abundant food than the old, will neglect 

 and perhaps abandon its old habits of flight. Then in disuse 

 the wings degenerate, and they assume in course of time, by 

 survival of such changes through several generations, a 

 changed hereditary character, while possibly the legs acquire 

 greater strength. This is a change which is perceivable 

 in our own period, and is fully described by observers of 

 the subject, and it is typical of what is constantly occurring 

 and unquestionably always has been prevalent. 



In comparison with human conduct the merely expedient 

 habit must be distinguished from the conscious purpose of 

 man's intelligent action, which is a comparatively recent 

 acquisition of humanity; and which produces variation in 

 quite a higher sphere of action, because it is selective and 

 voluntary. The primitive law of experimental benefit, how- 

 ever, still affects man in his lower nature, just as it always 

 did since it first arose in his primitive ancestors, when they 

 lived the life which we now observe in animals of that low 

 grade. The progenitors of mankind before the psychological 

 age were governed and varied and modified by this simpler 

 law of expediency. It is still part of the fundamental law of 

 conduct, and can be observed still effecting change in human 

 physique and human habits by the same processes. The 



