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THE AMERICAN NATURALIST [Vol. XLIX 



an enumeration of the known properties of a ' 'least 

 character. ' ' 



As distinguished from a group of characters the prop- 

 erties of a ''character" are its separability, its inde- 

 pendence, its individuality, its own rate of movement 

 ontogenetic and phyletic, its differentiation by these 

 properties from other least characters. Its separability 

 in heredity is shoivn where it can be hybridized. 



From the structural or anatomic standpoint a least 

 character is a group of cells and tissues constituting a 

 diminutive organ or part of an organ subserving a dis- 

 tinct though subsidiary function. For example, the <e pli 

 caballin" in the enamel of the horse's tooth or the rudi- 

 mentary cuspule may be cited as least characters, for 

 each is composed of a vast number of cells and more than 

 one tissue, but seems to have the property of rising or 

 falling and behaving like a unit. 



11. "Least Characters" in Classification and Systematic 

 Work 



This " least-character" conception is of great value to 

 the zoologist and botanist in systematic work, this con- 

 ception of an individual as a colony of "characters" each 

 with its principles of independence and its principles of 

 correlation, germinal in origin but subject to somatic 

 modification by environment and habit. 



First, among these single characters are those ob- 

 served by Waagen which accumulate until they build up 

 into one of his "mutations." One or more such single 

 characters compose the "mutants" of De Vries. 



Second, the old but oft-confusing term "races" be- 

 comes clear; we may now understand the significance of 

 the races of the horse, for example, the Arab, the Forest, 

 the Steppe horse. These races are all fertile inter se 

 and thus have never been defined as species although fer- 

 tility and non-fertility are no more important in the dis- 

 tinction of species than any other "character." The 

 characters which distinguish races are, nevertheless, often 

 of specific value; they are either proportional or numer- 



