60 INTRODUCTION. 



ric name those species which were more striking instances of 

 the Linnsean groups. In extensive modern genera it has still 

 even been found serviceable to introduce minor divisions, 

 which in like manner facilitate the acquisition of knowledge. 

 It is, however, the opinion of some authors (as, for instance, 

 Mr. Vigors, in the Zoological Journal), that their existence 

 ought not to be admitted ; or if they present sufficiently dis- 

 tinctive characters, they ought to be regarded as genera, 

 and the next higher group of which they form a part, as 

 sub-families. That the gradual approximation of form in 

 the most extensive groups, (where, for instance, it must be 

 admitted that the series, from the number of species, is evi- 

 dently least unbroken), prevents us from assigning such dis- 

 tinctive limits to our groups, whether of genera (that is, 

 speaking theoretically) or sub-genera, as shall comprise 

 those particular species, in which the characters of distinct 

 genera are blended together, cannot be denied; and the 

 great genus of Carabidcs (Feronia) has frequently been 

 cited. But still, even in these kind of groups, we find vari- 

 ous types of form, which, in the typical species of each minor 

 group, are so well marked, that if the genus were less nume- 

 rous in species, entomologists would not hesitate to consider 

 them as so many distinct sub-genera. But by many natu- 

 ralists the great chain of nature is regarded as formed upon 

 this very mode of confluent characteristics ; and were we to 

 admit, in those most extensive, and consequently, as we may 

 well suppose, most perfect series of species, the non-existence 

 of genera or sub-genera, we should be compelled to admit 

 still further, that there is no such thing in nature as any 

 other distinct division than that of species. " It appears to 

 be the opinion of most modern physiologists," observes 

 Messrs. Kirby and Spence, " that the series of affinities in 

 nature is a concatenation or continuous series; and that 

 though an hiatus is here and there observable, this has been 



