74 GEOLOGICAL MEMOIRS. 



luxuriance of tlie forest regetation ; but other important circum- 

 stances must have co-operated in the cleTelopment of the fauna and 

 flora generally, and especially in that of the Coleoptera. The Bu- 

 prestes, therefore, are interesting in a geological point of yiew, enter- 

 ing into creation at an early period, predominating amongst the Wood- 

 chafers in the tertiary period, and occupying an important place in 

 the history of the deyelopment of the Beetle-tribes. 



What the Buprestidce are amongst the land-beetles, the Hydrophi- 

 lidce are amongst the water-beetles. Our waters are mhabited by- 

 two chief Beetle-famihes, the Hydrocantharides and the Palpicornes. 

 At present the former predominate, and indeed not only with us, but 

 also in the hotter countries. In the tertiary period, on the other 

 hand, the Paljncornes decidedly predominated, and that especially 

 through the Hydrophili. Not only do they occur hi a long series 

 of species, but also in gigantic and remarkable forms, unmatched by 

 any hying species ; indeed one yery pecuhar genus (Escheria) is be- 

 come altogether extinct. That this predominance of the Palpicornes 

 was not dependent on local causes, will be shown by the fact, that as 

 yet there are known four species oiPcdpicornes and only one Hydro- 

 canfharis from the chalk, three species of Palpicornes with one Hy- 

 drocantharis from the Jurassic beds, and that at (Eningen and Ra- 

 doboj together about twice more of the fonner than the latter occur ; 

 whilst, on the contrary, in the present world, were we to compare the 

 relatiye proportion, either generally or m the Swiss fauna, there are 

 known about twice -move Hydrocantharides than Palpicornes inhabit- 

 ing the waters. In fine, the water-beetles, as also the land-beetles, 

 haye commenced with the more incomplete forms — the yegetable- 

 feeders, and only at a later period were the more highly organized 

 carniyorous water-beetles brought into existence. 



From this examination of the history of insects arises the question*. 

 Is there naturally a deyelopment of the perfect from the imperfect, 

 or is the introduction of different plants and animals enrirely influ- 

 enced and guided by external chcumstances, by chmate, and by local 

 conditions ? These latter chcumstances are doubtlessly of the highest 

 importance. But we also see that similar chmates produce altogether 

 different forms, as a comparison of the natm'al history of North Ame- 

 rica and of Em'ope, or of districts eyen lying nearer together, will show 

 us. Hence we see that climate is not the only determinating condition, 

 and that typical differences exist under similar chmates ; a harmony, 

 at the same time, existing between the plant- and animal-types and 

 the chmate in which they hye. Taking into consideration the influ- 

 ence of external circumstances, we are prepared to expect that aquatic 

 animals and plants must necessarily haye been the earhest organisms, 



* With great pleasure I find the author, altogether independently and of his 

 own accord, by the examination of fossil insects, arrive at similar conclusions with 

 regard to the la^vs of the development of organic natui-e, to such as, from the 

 study of fossil remains, I have given in the ' Geschichte der Natur, AbtheU. Enu- 

 merator Palseontologicus ;' viz. (1.) the law of gradual perfection in its peculiar 

 modification, governing through (2.) the law of progressive relation of organiza- 

 tion to external conditions ; thence (3.) the law of increasing diversity. — Broxx. 



