Hyatt.] 116 [Aprils, 
utcd into the ditfcrent gcnora arising from tlu>m. In snch cases 
the radical may be considered as an undeveloped series and sepa- 
rated as a distinct genus, though it consist of only one species 
with well-marked varieties." "All we want to alter in this," says 
Professor lilake, "is to substitute 'lineage' or some equiA'alent 
word for 'genus' and 'form' or 'mutation' for 'species.' " 
The objection made by Professor Blake rests on the assumption 
that a genus may be defined to be a group "of contemporaneous 
species." This term as used in botany, zoology, and paleontology 
is obviously a convenient name for a group of organic forms, called 
species, which are unitable by common characteristics. The 
common use of the term "genus" and also that of "species" includes 
no reference to time, to location, or to any theoretical connections 
that may be made between the organisms. 
The opinion that the employment of old words in new senses 
increases the difficulty of all scientific exposition by obliging the 
mind of the reader or student to act in opposition to fixed habits 
of mental association, has been u])held in this i>aper. It has also 
been tacitly assumed, that the effort to assimilate a new word is 
slight compared with that required to enlarge the meaning of an 
old term, involving as it does two distinct mental o])erations. 
Such remarks, however, can be legitimately applied onlj^ to terms 
having acquired a more or less fixed definition and application. 
The terms of binominal nomenclature in organic research are, 
however, elastic verbal structures of a different class. The terms 
genus and species have never acquired a fixed definition and like 
those of all other categories of taxonomy have been perj^etually 
changing in application. There has been of course a steady gain 
in the mode of regarding the species and genus, in so far as the 
progress of knowledge has led naturalists in every department to 
construct their classifications more and more in accord Avith the 
natural relations of organisms. 
They have been used by every writer as an elastic medium for 
the expi'ession and explanation of tlie results of his researches 
into the relations of forms. ''I'hns, in my own researches I have 
arrived at what I think is an approximately satisfactorj'^ definition 
of a genus and do not se(^' what i>5 to be gained l)y calling this 
class of grou])s by another nanie, as the old term genus seems to fit 
exactly. The use of the word "genus" calls attention to the very 
fact that T wish to insist upon, viz.^ that this is a novel and natu- 
