of certain species of Wt'Iloir. — Part 2nd. 240 



that the genera Emphytus and Dolerus cannot be separated from the 

 former by any impassible barrier. Systematists are by no means pleas- 

 ed with such cases as these, because they undermine the foundations 

 of their theories; and such writers as are scientifically dishonest, often 

 wilfully ignore and conceal them. But they are especially interesting 

 to the philosophic naturalist, as showing how one genus gradually 

 passes into another, and how genera have no real ever-permanent ex- 

 istence in nature, but are mere contingent eventualities, dependent up- 

 on the circumstance of whether a certain number of intermediate spe- 

 cific forms have perished or not from off the face of the earth, or have 

 escaped or not the researches of collectors. " The Coleopterous genus 

 Brachys," says LeConte, "forms several distinct groups, which I should 

 consider as genera, but that Lacordaire states that they merge impercep- 

 tibly together." (Trans. Ann. Phil. Sue XI, p. 251.) On similar 

 principles the very extensive old Geodephagous genera Agonum, Pla- 

 tynus and Anchomenus, and the almost equally extensive old Hydrade- 

 phagous genera Hydroporus and Hygrotus, have been amalgamated ; 

 while, on the other baud, small genera, containing only a few species. 

 are every day being cut up into new genera, each containing ouly one 

 or two species, thus making the rich richer and the poor poorer still. 

 In Lepidoptera, according to the Rev. Mr. Green, there is a biennial 

 revolution in England in generic nomenclature ; and in Heuiiptera Amy- 

 i»t and Serville expressly avow it as their plan, whenever they cau es- 

 tablish any difference whatever between two species sufficient for a ge- 

 neric subdivision, to found new genera wherein to place each differing 

 species. ( Ilemipt. Introd. pp. vi — vii.) Where are now the old Linnaian 

 genera ? Scarcely a single one remains in the old Linnaaan acceptation 

 — all have been cut up into small fragments, and are being daily split 

 up still finer, then, perhaps, re-united, and then once more split up in- 

 to minute fragments ; while the Linnasan species — with a few excep- 

 tions, due to misinformation or error on the part of the great founder 

 of Natural History — stand like a rock, and will stand for indefinite 

 ages. And yet we are gravely told, that genera have as real an exist- 

 ence in nature as species! 



The genus Euura (anglice "well-tailed") takes its name from the 

 unusual length of the anal styles or " cerci ;" (Westw. Introd. IT. p. 

 93, note;) but this character occurs only in the ? , the % % of both 

 Euura and Nematus having very minute cerci. Why unusual length 

 of 9 cerci should be invariably, so far as I am aware, correlated in 



PKO< EEDIKGS EST. SOC. THILAD. DECEMBER, 1S6(5. 



