8 VARIATION 



Some dogs (bloodhounds) trail marvelously well ; others (grey- 

 hounds) scarcely at all. Some hens lay more eggs than others, 

 and of different color and size. 



Some animals are hard feeders, while others lay on flesh 

 readily. Some beef is coarse in its grain ; other is fine and ten- 

 der. Some is well marbled with fat ; other is not. Sometimes 

 the flavor is delicate ; again it is rank, and often it is insipid. 



No two trees are alike in their growth or branching habit, 

 though similar within the same variety, and the widest difference 

 is often found in leaves from the same tree. 



Differences extend to minute particulars and include all charac- 

 ters. The student should early form a clear conception of the 

 fact that differences extend to all characters however insignifi- 

 cant or minute. Besides, he should understand that they include 

 function as well as structure, and that not only external anatomy 

 and conformation are involved but internal organs and their 

 activity as well, and no greater mistake can be made than to 

 define evolution as "a study in morphology." 



If we so define the word " variation " as to cover any change 

 in detail of structure or function which our faculties enable us 

 to detect, then we may say that variation extends to all charac- 

 ters, internal or external, structural or functional, and if the 

 study lay in the realm of ethics, economics, philosophy, or reli- 

 gion, we should add, material or immaterial. 



The individual is therefore so distinctly a unit that its iden- 

 tity is at once recognized and the principle is conceded that " no 

 two are alike " and that variation is universal. 



Limitation of variability. The exception to the universality 

 of variability is in the realm of non-living matter. The specific 

 gravity and other properties of iron, gold, sodium, or chlorin 

 are constant, and their relations and combining powers with 

 other chemical substances are, under identical conditions, invari- 

 able and therefore well known. 



Oxygen, hydrogen, and even nitrogen and carbon, combine 

 always in definite proportions, and though their combinations 

 are exceedingly numerous yet when the conditions are known 

 the exact combination can be foretold ; moreover the properties 

 of this combination will not only be definite but they will be 

 identical with those of all other similar compounds. In this 



