BANK OF CIRCULAR GROUPS. 34>Q 



cularity can be traced ; but in some few instances this 

 can be done : we are, therefore, justified in believing 

 they would invariably possess this property, were they, 

 in all instances, equally abundant in species. Sub- 

 genera thus become the lowest circular groups in nature, 

 or, in other words, they are the first assembling together 

 of species : all of which belong to the same type of form- 

 ation. Nearly all the modern genera are, therefore, in 

 fact, sub-genera, because every deviation from a type of 

 formation is made into fc a genus ;" but no effort is made 

 to assemble these types under those intervening groups, 

 which come between genera and families. It has never- 

 theless been repeatedly proved to demonstration that two 

 intervening circular groups do actually exist in nature ; 

 and which, as already stated, are bond fide genera and 

 sub-families. The modern practice of defining and naming 

 these sub -genera is very useful, provided their true dis- 

 tinctions are conspicuously noted ; but, as the theory of 

 definite variation (415.) has hitherto received no atten- 

 tion, at least in entomology, it frequently happens that 

 the essential characters are overlooked, and the unimport- 

 ant ones brought forward. As an example of sub-genera 

 really natural, we must refer to the f( Zoological Illus- 

 trations," where the reader will find all those of the 

 genus Polyommatus described and figured. It will be fur- 

 ther remarked, that these sub-genera are to be regulated 

 in their selection by the same laws as are applicable 

 to higher groups. Their individual circularity, indeed, 

 cannot be always Jtraced, unless they are united in their 

 proper genus, as in Polyommatus; they will then re- 

 present all the higher divisions of their own order. The 

 sub-genus Polyommatus, for instance, stands at the head, 

 as representing Papilio Lath. Next follows Lycana, 

 or the copper butterflies, united most completely to the 

 last, and representing Nymphalis Lath. Na'is comes 

 next, as typical of the Hesperidee. Lucia represents the 

 Erycinidce; and Erina brings us again to Polyommatus, 

 with which it not only unites, but represents in itself 

 the Satyridce. Now, each of these, according to the 



