The end of the ovipositor is developed into little projections, some of which are armed with hard, sharp points, which act exactly like the cutting edge of the auger. This elaborate appliance is necessary on account of the thick, tough skin of the ox, which the Gad-fly has to penetrate before it can deposit its eggs. Perhaps the reader may be aware of the fact that the modern system of cutting channels in stone with the diamond point, as was so well exemplified in the Mont Cenis Tunnel, is but an imitation, and an imperfect one, of the method adopted by the Gad-fly. We shall soon recur to this instrument. STRIKING TOOLS. If we search the records of antiquity as left by races of men that have for countless ages vanished from the face of the earth, we shall find that in some shape or other the Hammer was a tool in constant use, and that in principle, though not in material, there was no difference between the Hammer of the Stone Age and that of a blacksmith of the present day. The development of the instrument can easily be traced, especially as it is a tool which does not admit of much elaboration. The original hammer was evidently a simple stone, and answered equally as a tool and a weapon. As, however, man progressed towards civilisation, he found that the stone itself was insufficient for his needs, and that he required much more force. The most obvious mode of doing so was to take a larger stone, but this expedient soon became valueless, inasmuch as a large stone was a cumbrous instrument to handle, and could not be directed with any certainty or delicacy. The principle of the lever was then applied to the stone, which was affixed to a handle, and thus became elevated into the rank of a comparatively civilised tool. Sometimes the stone had a hole bored through it, into which the handle of the hammer was inserted, as is the case with most of our present hammers and pickaxes. Sometimes the end of the handle was enlarged, and the stone thrust through it, as is now done with the axes of Southern Africa. Sometimes a long, flexible rod was used by way of handle, the centre of it taking two turns round the stone, and the ends being lashed together. Handles thus made may be seen in any blacksmith’s forge of the present day. The tool thus made was soon developed into various forms for different uses. By lengthening and pointing the head, it became a pick for loosening the earth. By widening and flattening the head, it became a hatchet; and, by performing the same alteration in the pickaxe blade, it became an adze. I possess a singularly ingenious tool from Borneo, in which the head is movable, so as to be used as a hatchet or adze at pleasure.