HEER ON THE HISTORY OF INSECTS. 75 



in consequence of the predominance of the primseval ocean ; and we 

 find also, that these inhabitants of the water in general have a lower 

 grade of organization than the land plants and animals. Thus it is 

 evident that both of the great organic kingdoms of nature have pro- 

 duced their lowest, and at the same time their earliest, forms in the 

 water. As dry land arose, so also must have arisen new conditions 

 favourable for the existence of a multitude of new plants and ani- 

 mals ; and that so much the more, the more the firm land increased in 

 extent and in heterogeneousness of composition. And, in accordance 

 with the conformity existing between the extent of the inorganic and 

 the organic relations of the earth, the evolution of the more and more 

 varied conditions of climate, soil, &c. would be steadily accompanied 

 by more and more manifold forms of animal and vegetable life. 

 Evidence of this progressive change is to be seen in the case of In- 

 sects ; and is especially shown by the above-mentioned relative pro- 

 portions existing between the Metabola and the Ametahola ; the 

 latter, of inferior organization and with imperfect changes, appearing 

 first on the stage, and, in the early periods of the earth, predomi- 

 nating over the former. There being no marine insects, this animal 

 type could first come only with the formation of dry land. Of the 

 Articulata, to which class of animals the Insecta belong, the subor- 

 dinate Crustacea first appeared, predominating, through the Trilo- 

 hites, in the earliest geological periods * . 



There are also some striking examples, previously given, in the in- 

 dividual orders of Insects, of the appearance of the more imperfect 

 forms before those of higher organization. The Hymeyioptera and 

 the Dipt era, however, appear to form an exception. If in the Di- 

 ptera we begin with the Brachocera as the more imperfect, and ascend 

 from them to the Nemocera, we ought in the Hymenoptera to place 

 the Bees lower than the Ants and the Ichneumon-flies. This arrange- 

 ment certainly does not seem natural. The Bees appear to me to 

 belong to the head of the Hymenoptera, and the IchneumonidcE to 

 occupy a subordinate rank. The Muscidce, among the Dipt era, are 

 analogous to the Bees, but the Ichneumonidce have as their analogue 

 the Nemocera, so that the latter appear to stand lower than the 

 former, and this is supported by their more imperfect wing-structure. 

 Under these considerations, the Hymenoptera and the Biptera would 

 not altogether contradict the general rule, that the earth, both in the 

 formation of its surface and in all its habitants throughout the course 

 of time, had received continual improvements 



A second important conclusion that I believe may be drawn from 

 the above inquiry into the history of the Insects is, that the older an 

 animal type isj so much the more are the tertiary related to the ex- 

 isting forms of that typef . Each type also commences with peculiar 

 forms, and then gradually approaches to those of the present time. 

 The Vertebrata clearly show this ; of these, the fish first appear 



* [Compare Prof. Agassiz's '' Geographical Distribution of Animals," Christian 

 Examiner, 1850, p. 195. — Ed.] 



t This is authenticated, both generally, and among Mammalia in particular, in 

 the ' Geschichte der Natur, Enumerator.' S. 739 ff., 909 ff., 936 ff.— Bronn. 



