ENTOMOLOGY EOCENE PERIOD. 



469 



long remain so ; but this is very immaterial if they 

 facilitate the ready recognition of described species. 

 The value of a system in the present state of our 

 knowledge must be limited to that object, that 

 there may be no difficulty or error in recording, in 

 connection with the identical species, whatsoever 

 observations whether anatomical, physiological or 

 economical may have been made upon it. A true 

 natural system must be founded upon such a mass 

 of knowledge that we can never hope thoroughly 

 to possess it ; for even when we shall have arrived 

 at an intimate acquaintance with their external and 

 internal organization, much still remains to be 

 done. Something may be contributed by analogy, 

 but which it is not safe to trust to until fully con- 

 firmed ; for nature is frequently apparently eccen- 

 tric, from the impossibility of our arriving at cor- 

 rect conclusions as to the relative effects of the 

 complicated combinations of organization, and their 

 mutual dependence upon the instincts and habits of 

 the creatures. Indeed, in those systems which are 

 most profuse in their professions of adhering to 

 nature, we remark the strange incongruity of 

 no value being given to instinct ; and that crea- 

 tures with instincts limited to self-preservation and 

 the propagation of the species, assume an undue 

 superiority, from the mere circumstance of having 

 an organ or two more elaborately constructed in 

 the mouth, over such as possess a highly developed 

 instinct, and live in a peculiarly organized social 

 state, which necessarily implies the power of com- 

 municating ideas and a certain degree of ratiocina- 

 tion. 



It is here perhaps the most convenient place to 

 take a cursory notice of the doctrine of circular 

 affinities, intended to supersede, as more natural, 

 the older one of linear gradation, in the distribu- 

 tion of organized beings. Mr M'Leay, the cele- 

 brated author of this system, conceives that the 

 arrangement must be made in a series of circles, 

 each composed of five groups, which are the affin- 

 ities, and the corresponding groups of the approxi- 

 mate circles the analogies of organization ; and by 

 this means the whole series of created beings are 

 linked together in closer connection than by any 

 other mode of distribution. The idea is exceed- 

 ingly attractive ; but although it apparently in some 

 instances fulfils our expectations, yet in others the 

 distortions are so palpable, that we are surprised 

 that the learned author himself seriously adopted 

 it. The different combinations and structure of 

 organs very distinctly produce a reticulation of re- 

 lations; but to circumscribe nature within a circle, 

 and that circle composed merely of five members, 

 is to straiten her capacity too closely ; for she, to 

 use the words of Huber, " a varie a I'infini ses com- 

 fjinaisons." The most obvious mischief produced 

 by the promulgation of such doctrines is to with- 

 draw ardent and enthusiastic minds from the la- 

 borious and steady observation of nature from 

 which alone we can derive true knowledge to the 

 pursuit of a phantom, which, when overtaken, 

 melts in our arms. 



In connection with our observations upon system, 

 we may here remark upon the apparently ambi- 

 guous division of genera, with respect to the num- 

 ber of species they contain, and which scarcely ac- 

 cords with the precision and steady progression of 

 nature, and is, perhaps, strong presumptive evidence 

 of all but specific separation being unnatural. It 

 may possibly be argued that their function in the 

 universal economy requires it, from nature varying 



her usual mode of making a species excessively 

 prolific where she requires a more powerful action; 

 and to that effect, which only a certain organiza- 

 tion can produce, she is limited, by causes which 

 we are unable to investigate, in her power of exe- 

 cuting by means of one agent, and consequently 

 has recourse to several species to enable her to 

 perform what, in other cases, under different cir- 

 cumstances, she can do by means of one alone ; 

 but this, although the best reason which occurs to 

 us, is very vague, and far from satisfactory. 



The progress of Entomology has been accele- 

 rated chiefly by the revision of the systematic ar- 

 rangement, and its improved distribution into 

 families, by the vast addition of species constantly 

 making, and the many valuable monographs with 

 which the science has been enriched. It is utterly 

 impossible that we should here enumerate the 

 multiplicity of works that have been published 

 upon the subject. Those of Latreille, whom the 

 science has so recently lost, will always necessarily 

 rank pre-eminent among them. It was, doubtless, 

 by the impulse given by his labours, that the science 

 has advanced to its present state of comparative 

 perfection. He was the first who indicated the dis- 

 tribution of insects into families, in his " Precis des 

 Caracteres Generiqu.es" from which time, in each 

 subsequent work, he has progressively remodified 

 and improved it, up to the publication of his 

 "Families Naturelles," in 1825. His portion of 

 the second edition of Cuvier's " Reyne Animal," 

 published in 1829, presents us with the best gene- 

 ral synopsis of the science, up to the date of its 

 publication, that we yet possess. The science will 

 long deplore the loss of Illiger and Leach, whose 

 early labours gave such earnest of future valuable 

 service. We must not omit to notice among the 

 benefactors of the science, our venerable Kirby, 

 and that joint labour of love, his and Spence'a 

 " Introduction to Entomology," which, perhaps, 

 more than any other work ever published, has 

 tended to make votaries to its study. M'Leay 's 

 name, also, will necessarily occur, to whom, if 

 even his theories are not adopted, we must feel 

 grateful for the utility of his practical labours. We 

 must not, either, omit mentioning Gravenhorst, for 

 the sake of his labours upon the Staphylinidae, and 

 his great work, the " Ichneumonologia Europcea" 

 which he had in progress for twenty-five years, and 

 which contains 2914 8vo. pages, and the description 

 and scientific arrangement of 1288 insects of a 

 tribe, the impracticable nature of which was pre- 

 viously insurmountable to every individual who at- 

 tempted them. Nor must- we forget Meigen for 

 his systematic description of the European Diptera, 

 which cost him fourteen years' labour. In its ana- 

 tomical and physiological departments, the labours 

 of Straus-Durckheim, Chabrier, Leon Dufour, 

 Audouin, Marcel de Serres, Cams, Treviranus, 

 Miiller, Suckow, and a multitude of others, dis- 

 persed throughout the numerous periodicals and 

 transactions of the various scientific societies, have 

 done much to illustrate the subject. 



EOCENE PERIOD; one of the divisions of 

 the tertiary epoch, according to Mr Lyell's sys- 

 tem, trom bus, aurora, and xttitos, recens, the com- 

 mencement or dawn of the existing state of the 

 animate creation. It includes, of Marine beds, the 

 Paris and London basins ; Freshwater beds, alter* 

 nating with marine, in Paris basin, isle of Wight, 

 Cacurbrine in Auvergne, Cantal and Velay ; and 

 the oldest volcanic rocks in Auvergne. Of 1238 



