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ME THODS OF INVES TIGA TION. I I5for the year 1693, embodies the following highly interesting data.Havingrecorded the results of the application to Infusoria, with a needle's point, ofvarious substances producing no "very important effects, he says Tinctureof salt of tartar (tartaric acid?} put with them in the same manner killsthem more immediately, but yet they will be first so sick or so affected,call it what you please, as you may see by a surprising convulsive motion,they will grow faint and languid apace, and you may see them fall to thebottom of the drop upon your object plate, dead but in their own shapethat they were in before you applied your needle, and will neither be flatas with spirit of vitrol, nor cylindrical as with common salt liquor but lie;dead in the same shape as before you put in your needle with the salt oftartar.Sack will kill them, but not so speedily as the other liquors."Methods of Investigation.To the working microscopist a hint or two will probably prove acceptablewith reference to the mechanical means that may be most advantageouslyresorted to in the investigation of the structure and life-historiesof the more minute, and comparatively unfamiliar, representatives of theInfusorial series. These, as typified byFlagellata, necessarily demand inthe several orders of the classconjunction with the high-power objectglassesthat are indispensable for their correct appreciation, more delicatemethods of manipulation.A chief obstacle encountered in the employment of these short-focussedlenses presents itself at the outset in the matter of penetration. Howeverthin may be the covering glass employed, it rarely fulfils the needs of theinvestigator, and mostly causes both inconvenience and loss of time onaccount of its extreme brittleness. Where the objects under examinationare attached to more solid substances, such as the stems of water plants,this rigidity and brittleness of the covering glass hampers progress in a mostprovoking manner, and materially restricts the limits of clear vision. Theunsuitability of ordinary covering glasses for the special investigations herealluded to, was long since recognized by the present author, and a substituteprovided that has been productive of the most satisfactory results. Thematerial utilized for this purpose was no other than the one extensivelyemployed, previous to the introduction of specially prepared glass, for thepermanent mounting of microscopic objects. This substance, representedwith a littleby ordinary talc as extensively used for gaselier shades, maypractice be split into laminae of such extreme tenuity that they may beblown away with the lightest breath, while for perfectevenness and transparencythey will compare favourably with the finest manufactured glass.With the employment of these talc-films the investigation of Infusoria withthe TV, ?V> or even the ^-'mch objectives becomes a comparatively easy task.The material in question possesses the further considerable advantages ofbending readily and permitting the object-glass to be brought close downI 2