ILLUSTRATIVE OF NATURAL SELECTION. 1638 
minifera,”’ he states that “there is not a single specimen 
of plant or animal of which the range of variation has 
been studied by the collocation and comparison of so 
large a number of specimens as have passed under the 
review of Messrs. Williamson, Parker, Rupert Jones, and 
myself, in our studies of the types of this group ;’? and 
the result of this extended comparison of specimens 
is stated to be, ‘‘ The range of variation is so great 
among the Foraminifera as to include not merely those 
differential characters which have been usually accounted 
SPECIFIC, but also those upon which the greater part 
of the GENERA of this group have been founded, and even 
in some instances those of its oRDERS”’ (Foraminifera, 
Preface, x). Yet this same group had been divided 
by D’Orbigny and other authors into a number of 
clearly defined families, genera, and species, which these 
careful and conscientious researches have shown to 
have been almost all founded on incomplete knowledge. 
Professor DeCandolle has recently given the results 
of an extensive review of the species of Cupuliferz. 
He finds that the best-known species of oaks are those 
which produce most varieties. and subvarieties; that 
they are often surrounded by provisional species; 
and, with the fullest materials at his command, two- 
thirds of the species he considers’ more or less doubt- 
fal. His general conclusion is, that ‘in botany the 
lowest series of groups, SUBVARIETIES, VARIETIES, and 
RACES are very badly limited; these can be grouped into 
SPECIES a little less vaguely limited, which again can 
be formed into sufficiently precise cunnra.” This 
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