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 (Lyccena), 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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