﻿NORTH AMERICAN SPHINGIM. 107 



We perceive here, why and how the characters of a genus should flow from it, and 

 not be created by them or rather made dependent on them. When we possess all 

 the conformable ideas included in the several specific creations which may constitute 

 it, we have a series of special modifications of some dominant conception, carried out 

 in a variety of conformable modes throughout entire specific cycles, and indicative of 

 special relationships to external conditions and the necessities of individual existence. 

 Generic characters should therefore be found in specific biographies, in instincts and 

 habits, in the embryo and the course of its development, as well as in the parts of the 

 mature being, since the conception exists in nature precisely as does that of species. 

 The genus is neither more ideal, nor more real than the species ; the latter consists of 

 a single specific conception, whilst the former is usually, but not necessarily, composed 

 of many such conceptions. 



. It is particularly difficult to indicate the limits of a genus. To determine it, entire 

 specific histories must be compared, and a rigid comparison instituted between the 

 ultimate structural peculiarities, of some of the parts, of the perfect beings. For, 

 within the limits of a family, or many genera differing amongst themselves simply in 

 degrees of relationship, if we regard the mature being alone, we find that form is the 

 same, that there is no difference in the degree of complication of structure amongst 

 the several secondary groups, but simply in the details of the development of parts 

 essential to existence, or at least intimately connected with the internal organization. 

 When generic separation of species becomes necessary, specific conformity in some 

 part of their cycles, or in these portions of ultimate structure, becomes aberrant to a 

 degree that is suggestive of divergence. Sometimes this disagreement is most 

 apparent in the embryo, or in the course of its metamorphosis ; or is most developed 

 in the imago, or in all these states united. Wherever it may occur in the specific 

 cycle, it is always expressed in some part of the perfect being, but by no means in the 

 same part of the structure of the different groups. Even in the same group, individual 

 variations or disagreements in particular organs take place, but the general con- 

 formity to the dominant conception involved in such individuals, is too observable to 

 authorize separation, and hence they are indicated as distinct groups within the generic 

 cycle. Hence it is, that no special organ, or part of structure can be assumed as the 

 basis of generic separation of individuals, in any of their states ; for, it is by this in- 

 dividual latitude and variation, that the chain of relationships within families, and 

 even beyond them, is maintained in organic beings. 



Practically, however, the systematist must classify natural bodies chiefly from a 

 knowledge of them in their perfect states, for in this condition they fall under obser- 

 vation most commonly, and are most readily studied. Systemization on this basis 

 is the first step in the study of every local fauna, and it is upon this, that its subse- 

 quent evolution and the study of specific histories must be placed. It is necessary, 



