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 

 Phcenius and Scarabceus. 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 132. 



