MORPHOLOGICAL VARIATION 29 



because extremes both ways are in most cases to be avoided, 

 and the highest excellence and the most reliable breeders will 

 commonly be found among the individuals of medium size. 



Differences in form, arising from relative inequality in devel- 

 opment of structural parts, are of more consequence than are 

 differences in mere bulk, in which development has been pro- 

 portional. This is especially true in horses, in which differences 

 in relative development of structural parts may seriously affect 

 the appearance or interfere with the action of the individual. 

 And so it is that, while morphological differences are of far 

 more significance to the student of general evolution than they 

 are to the farmer, they yet constitute a phase of variation not 

 to be overlooked by the student who is interested in the improve- 

 ment of domesticated forms. 



ADDITIONAL REFERENCES 



DARWINIANA. By Asa Gray, i vol. 



DARWINISM. By A. R. Wallace, i vol. 



EXPRESSION OF THE EMOTIONS IN MAN AND ANIMALS. By Charles 



Darwin, i vol. 



FROM GREEKS TO DARWIN. By H. F. Osborn. i vol. 

 LAMARCK: His LIFE AND WORK. By A. S. Packard, i vol. 



