VARIATION IN GENERAL 



2 3 



muscular activity, glandular secretions, etc. They are either 

 quantitative or qualitative, continuous or discontinuous, though 

 rarely the latter. 



A clear understanding of these distinctions is necessary to an 

 intelligent study of the nature and causes of variation. Accord- 

 ingly enough attention will be given to each to acquaint the 

 student with the way in which variation behaves, partly for its 

 own sake and partly as preparation for careful inquiry into 

 methods of dealing with deviations in those plants and animals 

 that we have domesticated and appropriated to our use, and 

 which we would see still better adapted to the purposes of man. 



Summary. Variability is the universal rule among living 

 beings. Literally no two are alike. The differences extend to 

 all characters and to the most minute particulars. Non-living 

 compounds exist in definite proportions, and their qualities are 

 constant, not variable. Variability is the only basis for improv- 

 ment. No improvment is possible, in the strictest sense of the 

 term, with respect to inorganic compounds, but living matter being 

 variable is capable of change and therefore of improvement. 



Variation consists not in the introduction of new character^ 

 but in different proportions or relations among the old ones. 

 All characters are racial, and all individuals actually possess all 

 the characters of the race and none other. This is shown by the 

 characters that are transmitted to the offspring. 



The unit of variability is in no sense the individual, though he 

 must be accepted as the unit for selection. The real unit of devia- 

 tion is the racial character, but back of that, in a biological sense, 

 lie the elementary characters or physiological units, whose vari- 

 ous combinations constitute racial characters. 



Variation is both quantitative and qualitative, both continuous 

 and discontinuous, and these distinctions should be clearly in 

 mind at all times. 



SPECIAL EXERCISES 



Prepare a list of variations that are (i) quantitative, (2) qualitative, 

 (3) morphological, (4) substantive, (5) meristic, (6) functional, (7) con- 

 tinuous, (8) discontinuous. 



