(k]4 [December 



either exactly or almost exactly alike, and that a species. *S^. batatas, 

 which inhabits a polythalamous twiii-gall of a totally different struc- 

 ture, is comparatively speaking widely distinct from the first — after we 

 have traced the same law even in the larvae, and found that those which 

 inhabit the bud-galls are yellowish with whitish markings and all exactly 

 alike, and that which inhabits the twig-gall is sanguineous marked 

 with yellowish and has a totally different breast-bone — after we have 

 seen the Gruest (lall-gnats, not themselves making any galls, but dwelling 

 in galls constructed by the true Gall-makers, generally in those of such 

 species as are allied to themselves, and but rarely in those of species be- 

 longin": to different Families and different Orders, and one of them, Gev. 

 albovittata n. sp., so closely resembling a true gall-making (lall-gnat. 

 Cec. s. batatas n. sp., that at the first glance they can only be distin- 

 guished by a trifling difference in size — after we have remarked that 

 even authors, like Osten Sacken, who cannot be supposed to be led 

 away by any visionary theories, have dilated upon the great apparent 

 similarity between several species of true, gall-making Gall-flies and 

 the Guest Gall-flies that intrude upon their homes (Proc Ent. Soc. 

 Phil. II. p. 34) — the mind naturally enquires, what is THE meaning 

 of these and similar phenomena ? Natural History is not, as some have 

 foolishly supposed, a mere bundle of dry facts. The.se, it is true, form 

 the foundation upon which we must build, and, without such a solid 

 and immoveable base to build on, the whole edifice will crumble to dust 

 with the first blast that assails it. But Science, to be worthy of that 

 high and holy name, must not be contented with mere facts. Her aim 

 is to generalize upon those facts, when a sufiicient number of them has 

 been accumulated — to curiously pry into the laws which govern the 

 great system of which we ourselves form but an infinitesimally small 

 fragment — to ascend from minute details to broad and sweeping induc- 

 tions — in a word, to solve the great mystery of the Creation and explain 

 to us how, and why, and wherefore we exist. 



Geology has already told us much on this subject. Zoology, her 

 sister and hand-maiden, has also told us much and can tell us much 

 more. The GEoaR.\PHiCAL Distribution of species demonstrates, 

 that they cannot have all spread in their present specific types from 

 one common centre of creation, and that if we assume several distinct 

 centres of creation within the present geological epoch, we must assume 



