348 PRACTICAL AND SCIENTIFIC ZOOLOGY. 
group, — we shall never succeed, unless that definition is 
so constructed that it becomes definite,—that itmust have 
certain assigned characters, and that these characters, 
under different modifications, will be found in all other 
genera. Mr. MacLeay, no doubt, was impressed with this 
conviction, for he was the first who restricted a genus to 
an assemblage of species, in which five distinct modifi- 
cations of form were discoverable, and which he further 
illustrated by showing their actual existence in the genera 
Phenius and Scarabeus. Now, as this was the first de- 
finite explanation of a genus, we are surely bound to adopt 
it, not only as emanating from our learned countryman, 
but because, by rejecting this definition, and applying the 
term to another description of groups, we perpetuate a 
confusion of terms, without gaining a single advantage. 
Let every one be at liberty to call an insect or a bird by 
its generic or its sub-generic name; but let not these 
two sorts of groups be misnamed and lost sight of, even 
in our artificial systems, for they cannot be so overlooked 
in any natural arrangement, without a direct violation 
of that uniformity and consistency which are absolutely 
essential to such arrangements. A genus, like every 
other natural group, must, of course, be circular in 
its affinities, and it must likewise contain within itself 
certain types or divisions which shall correspond with or 
represent those of all other natural genera. We have just 
cited the examples that have been given of natural 
genera among the coleopterous insects ; and in the “ Zoo- 
logical Illustrations*” the reader will find another, 
taken from the lepidopterous order. The genus in 
question is that of Polyommatus, one of the most in- 
teresting to British entomologists, as containing all the 
beautiful little blue butterflies of our meadows. Up to 
this time these are the only genera in entomology which 
have been so verified. 
(430.) Sub-genera are the leading types or divisions 
just spoken of, as belonging to a genus. It is very 
seldom they are so numerous in species that their cir- 
* Second series, Plate 182. 
