18 JOUBNAL OF THE MiTCHELL SoCIETY [OctoheV 



We must recognize that precisely defined subgenera are ideas each 

 of which is actually represented by perhaps only a few forms. Many 

 other forms cluster round such central types in such wise as to be 

 intermediate between them, sometimes intermediate between two 

 types in respect to one character, and between two others in respect to 

 another character. 



All this militates against the making of too many systematic 

 groups, because in the end, if the characters of the concrete organism 

 are to be really recorded as they are, whatever groups are made, some 

 qualifying statements will usually have to be added to the designation 

 of the organism as of such and such a genus or subgenus. 



I am making no plea for looseness of identification, far from it. 

 But, incidentally at least, this paper does make a plea against at- 

 tempting to define too precisely the place in nature of an organism 

 through continued formation of new genera, or division of genera 

 into subgenera. At any rate, the subgenus when used should be 

 thought of, not so much as a subdivision but rather as one of several 

 types within the genus, subgeneric types, standards as it were. Cer- 

 tain organisms will be found practically to conform to some one of 

 these standards. While an organism that deviates can be briefly 

 described by stating its differences from some standard. 



Finally it may be pointed out that the relation of series, composed 

 of intergrading members (viz., species of Tetilla, e.g., with cortex 

 ranging from fibrous to non-fibrous) to the current Mendelian theory 

 of germinal units is plain. If we assume enough units, the theory 

 is applicable. But in thus enlarging the number to suit these facts, 

 the Mendelian units or genes come to be synonymous with what we 

 call hereditary properties. I mean the subtle, minute powers, many 

 of which may act in concert to produce a sensible effect, the kind of 

 germinal property which at its first appearance in the evolution of 

 a race or strain we call a small heritable variation, when for instance 

 we speak of the gradual summation of variations. In this way the 

 gene is removed from its somewhat isolated position in biological 

 thinking, and made available even to the systematist, who in adopting 

 it, however, must also adopt Semen's contention^ that all variation 



* Richard Semon. Das Problem der Vererbung "Erworbener Eigenschaften," 1912. 



