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134 SPONTANEOUS GENERATION.in either one of the four vessels, their germs beinghave entirely subsided.thus demonstrated toIn addition to the highly suggestive evidence adduced through theseseveral experiments, in demonstration of the persistency of form, and enormouscapacity for atmospheric diffusion, possessed by these monads, theirultra-microscopic spores or germs are now shown to possess varying degreesof ponderosity, and it would seem by no means beyond the range of possibility,by further research, and having regard especially to the length oftime occupied in the subsidence of a given type, to ascertain, by comparisonwith some larger and measurable variety, the exact or approximate dimensionsof those germs, as yet lying beyond the defining powers of our mostperfected microscopes, but instantly revealed by the searching electric beam,and which may be cultivated at will in an appropriate fluid medium.In addition to the very important bearings upon the question of spontaneousgeneration embodied in the foregoing researches, Mr. Dallinger'sname demands notice also with reference to some most important experimentsconducted alone, and in combination with Dr. Drysdale, for the purpose ofascertaining the power of resisting high temperatures possessed by theselower forms of life in both their adult and sporular or germ condition.These experiments entirely confirmed Professor Tyndall's observations,and possessed, moreover, the additional advantage that a given and varyingthermal death-point, or limit of heat-resistance, was now associated forthe first time with fixed and specific monad types. Following out thisline of investigation,it was thus shown that the spores of Tetramitusrostrata could successfully resist a temperature of 250 Fahr. (12 iC.), thoseof Dallingeria Drysdali 220, those of Cercomonas typica 260, while in thecase of Heteromita rostrata and H. uncinata they passed unscathed througha temperature of no less than 300 Fahr., or 148 C, which represents thehighest limit that has as yet been obtained. It was further ascertained thata somewhat different result accrued according to whether the heat wasapplied in a wet or dry form, the spores in certain instances exhibitinga difference of as much as 10 Fahr. in this respect, and the highestbeing resisted when applied in the dry condition. The adult and activemonads, having their constituent sarcode or protoplasm in a soft and semifluidstate, in all cases succumbed to the comparatively low temperature,as an approximate limit, of 140 Fahr., and inmany instances to one considerablylower even than this.Some results of the author's personal investigations have now to besubmitted, which tend, from an entirely independent point of view, towardsthe solution of the question now under discussion. Respecting ProfessorTyndall's highly valuable testimony, it has been, and may yet be, objectedby the partisans of heterogeny that his atmospheric germs are purely hypotheticaland intangible, not having been actually seen by him, nor, whatis more important, being so far connected with any recognized specificform of infusorial life. The evidence adduced by Messrs. Dallinger