122 THE DIRECT INFLUENCE 



stimulus and the reception of a possible impress 

 by the egg. 



Concerning the results from repetition of 

 stimuli in a series of generations, about the only 

 facts at hand are those obtained from a study 

 of variabihty as affected by nutrition, in which 

 it is found that more favorable conditions of nu- 

 trition increase the range, and that further in- 

 creases accumulate with the continuance or repe- 

 tition of the optimal conditions with relation to 

 successive generations. The foregoing may be 

 taken as a fair representation of the physiolog- 

 ical basis of the possibilities by which alterations 

 in the soma might be impressed upon the germ- 

 plasm and transmitted to successive generations, 

 and a description of the authenticated observa- 

 tions and well-ordered experiments which have 

 been made by skilled workers in dealing with this 

 subject during the last few decades would form 

 no mean record. It would entail a historical re- 

 view far too voluminous for the present occasion. 

 However, among other general features it appears 

 that plants moved to habitats and to cultivated 

 fields to the northward and southward have been 

 seen to take on a seasonal rhythm in accordance 

 with the new climatic conditions encountered. 

 Unusual temperatures and foods have caused 

 marked alterations in structure, markings, com- 

 position of the body, periodicity of reproduction 

 and range of adjustment and endurance in both 

 plants and animals, but in all of these cases the 



