SUB-GENERA. 209 
dicative of their subordinate rank. The first process 
of generalising, or, in other words, the first stage of 
induction, is to bring an indefinite number of species 
into a group, which shall be so rigidly restricted, that 
little other variation is seen, among the individual 
species so associated, but such as arises from size, co- 
lour, or the greater or less developement of the same 
parts and the same organs. It is quite immaterial to 
our present purpose, whether we call these groups ge- 
nera or sub-genera ; but it is of the first consequence, 
that naturalists should agree in the meaning of certain 
terms or words. ‘That such groups as we have just 
described are natural, can admit of no doubt. The 
olives, the cones, and the cowries among the Testacea, 
are good examples; while, in entomology, we have 
the white garden butterflies (Pieris, Lat.), the blues 
( Polyommatus), the coppers (Lycena), the hair- 
streaks ( Thecla, Lat.), and the rove beetles ( Cicin- 
dela Lin.). In the British species of all these re- 
spective groups, we have a perfect illustration of the 
above definition of a sub-genus, and of that degree 
of variation which is found among species so grouped. 
Hence it follows, generally speaking, that the deter- 
mination of a sub-genus (or of a group so de- 
nominated) is one of the most easy things imagin- 
able; for, whenever we meet with a species which 
shows a marked affinity to any one of the above 
assemblages, yet possesses a peculiarity of structure 
which those have not, or wants another which they 
possess, We may in ninety-nine cases in a hundred 
conclude it to be the type of a sub-genus, which future 
discovery will most probably augment by other ex- 
amples, and which higher degrees of induction will 
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