NATURAL SELECTION 39 



derived from delicate cuticular sense organs. The internal 

 ears were probably once represented by minute bristle-like 

 organs in the skin, which probably were organs of touch 

 or for the perception of pressure. Remembering this most 

 important principle of change of function, we find that many 

 apparent difficulties in the way of understanding the origin 

 of structures in the body disappear. 



But the chief apparent force of the objection that in their 

 betrinnin^s organs could not have been of use lies in the 



O O O 



misconception that variation is very slight and that therefore 

 any organ would first appear as a very slight modification 

 and would progress by minute stages toward a condition in 

 which it could be of use. In reality variation is very con- 

 siderable, so that a structure at its first appearance may 

 be sufficiently developed to be of real importance to its pos- 

 sessor. What has been said of organs would apply as well 

 to instincts and other mental characters. 



Individuals which diverge to a very considerable degree 

 from the species average are often called sports. De Vries 

 and some others are inclined to believe that most species 

 have arisen as sports which breed true, handing clown to 

 their offspring their own peculiar characters. If this be true, 

 natural selection will still be operative to determine which of 

 these new species shall survive, only those persisting which 

 advantageously conform to the environmental conditions. 

 The derivation of new species from sports has been called 

 by De Vries, " mutation." 



A fourth objection, which is related to the latter two, is 

 that in our study of the fossil remains of extinct animals we 

 sometimes find that as we pass from the older to the more 



