The evolution theory . trictly speaking, understating the case, for, inthe crickets and locusts, for instance, there is a whole series of peg-like chitinous papillse (Fig. 86), the so-called bridge, each of whichmust have arisen by itself through variation of the corresponding spot of skin. At least I can see no orroundfor the assumption that the chitinoussurfaces on which the bridge is nowplaced would necessarily, from inter-nal reasons, have varied precisely inthe line of the bridge as it has done. Instructive examples of the co-adaptation of several parts to acommon action in organs which a
The evolution theory . trictly speaking, understating the case, for, inthe crickets and locusts, for instance, there is a whole series of peg-like chitinous papillse (Fig. 86), the so-called bridge, each of whichmust have arisen by itself through variation of the corresponding spot of skin. At least I can see no orroundfor the assumption that the chitinoussurfaces on which the bridge is nowplaced would necessarily, from inter-nal reasons, have varied precisely inthe line of the bridge as it has done. Instructive examples of the co-adaptation of several parts to acommon action in organs which arenot subject to the Lamarckian prin-ciple are afforded by the diversearranoements for cleanino^ the an-tenure, the bearers of the smelling-organ which are so important to thelife of insects (Fig. 102). Here eventhe adaptation of an indented areaon the tibia of the anterior leg tothe cylindrical form of the antennawhich passes through it, is sometimesso striking (Fig. 102, tah) that itmight be thought that it must have. arisen throuoh a o:radual wearino-out; 3et this is impossible, since we Fig. 102. Brush and comb on theleg of a Bee (Nomada). tib, end ofthe tibia, t^, first tarsal joint with thebrush and its comb {tak). Betweenthese and the tibial spine {tis})) withits lappet (L) the cross-section of an have to do with hard dead chitinousantenna (-40 is indicated. Drawn from ^ i j. -^.i a preparation by Dr. Petrunkewitsch. surtaces, and moreover not with a solid mass, like a hone, which is worndown by the knife, but with a hollow, thin-walled tube. In ants, bees,and ichneumon-flies this minute, semi-circular indentation containssmall, pointed, triangular saw-teeth, closely set like those of a comb {tak),and the apparatus is made usable by the fact that a iirm spine {tisj}), fusedto the end of the tibia, overhangs the notch and presses the antennatowards it. In many species this spine is double, or it is furnishedwith a thin comb or lappet (Fig. 102, X), or with rows of teeth,
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Keywords: ., bookauthorthomsonj, bookcentury1900, bookdecade1900, bookyear1904
