THE FRAGRANT CALLA 19 



The presentation of this subject puts us in 

 touch with one of the newest and doubtless one 

 of the most important aspects of the problem o^ 

 evolution. 



Since Darwin we have fully understood that 

 all evolution of organic forms must have its ori- 

 gin in variations. Xo two individuals even of the 

 same species are precisely alike, and it is not at all 

 unusual to find individuals of a species showing 

 very considerable differences, even as regards the 

 essentials of size and form and function. Indeed, 

 a certain range of such variations is considered 

 to be absolutely normal. 



One would never state, for example, that any 

 particular bird has a wing or beak or tail of 

 precisely a given length; instead of this the 

 ornithologist records the average or mean length, 

 or the limits of variation shown by different 

 specimens. 



And it is universallj^ recognized, since Darwm 

 gave us the clue, that the building up of new 

 species must be brought about through the selec- 

 tion of favorable variations. A bird with an extra 

 long wing, for example, might be able to fly a 

 little faster and secure its insect prey with greater 

 facility than its fellows ; and this slight advantage 

 might be instrumental in saving the life of such a 

 bird, and thus enable it to transmit its peculiarity 



