The Making of Species 



Many variations which organisms display are 

 of a mixed kind, being in part the result of inner 

 forces and in part due to the action of the en- 

 vironment. In so far as they are due to this 

 latter they do not appear to be inherited. 



Thus, although we cannot say of many varia- 

 tions whether they are germinal, or somatic, or 

 of a mixed kind, it is of great importance to keep 

 continually in mind the fundamental differences 

 between the two kinds. 



Some somatic variations are due to the direct 

 action of the environment ; they are merely the 

 expression of the manner in which an organism 

 responds to external stimuli. 



What is the cause of germinal variations? 

 This is a question to which we are not yet in a 

 position to give a satisfactory answer. 



The attempt to explain their origin plunges us 

 into the realm of theory. This doubtless is a 

 realm full of fascination, but it is an unexplored 

 region of extreme darkness, in which, we believe, 

 it is scarcely possible to take the right road until 

 more of the light of fact has been shed upon it. 



In the chapter dealing with inheritance we 

 shall indicate the lines along which it is likely 

 that future progress will be made. 



