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A UTHOKS INVESTIGA TIONS. 13 5and Drysdale may also be cavilled at as deficient of the necessary proofs,inasmuch as the various species with which their researches are connectedare peculiar to certain putrefying animal macerations only, and cannottherefore be said to fairly represent those types common to organic infusiongenerally, with which the phenomena of de novo generation have been heldmore especially to obtain.Now, among these, infusion of hayhas from the earliest date of thediscovery of Infusoria, and the promulgation of the doctrine of spontaneousgeneration, been recognized as the most productive material for the artificialdevelopment of these minute beings, and as the one in which such presumedde novo or spontaneous generation is most prominently manifested. Sofar, this seeming special potentiality of macerated hay has not been madethe subject of rigid and exhaustive inquiry, while the evidence recordedby Professor Tyndall concerning the extraordinary heat-resisting and infectiveproperties of hay-derived germs in their concrete form, is no doubtaccepted by the heterogenists as simply testifying to the possession bythis material of such potentiality. If, however, the disciples of heterogenyflatter themselves that from this last uninvaded vantage-ground they mayperadventure be able to withstand and bring discomfiture upon the advancinghosts of their opponents, the panspermists, they are destined tosignal disappointment.Within the last two years the animalcules produced so abundantly inhay-infusions have been the object of the author's special investigation,of this volumemany of the new species described in the systematic portionbeing, indeed, the outcome of such research.Hitherto the infusorial typescommonly observed in hay-infusions have been of comparatively largesize, belonging to the higher order of the Ciliata, and pertaining to suchgenera as Paramecium, Colpoda, Cyclidium, Oxytricha, and Vorticella.These, however, represent numerically but an insignificant minority comparedwith the vast hosts of flagellate forms which abound in a hay-infusionduring the earlier days of its maceration. In such infusions, watched fromday to day, and produced from hay obtained from different localities, thenumber of types presenting themselves in tolerably regular sequence wasfound to be perfectly marvellous. Foremost among the generic groupsputting in their appearance must be mentioned that of Heteromita, frequentlyrepresented simultaneously by three or four species, and including moreespecially the Heteromita (Manas) lens of O. F. Muller, H. caudata, andH. gracilis. Other genera, such as Oikomonas, Dinomonas, Petalomonas,Rhabdomonas, Ampkimonas, Monas proper, Cryptomonas, Hexamita, andGymnodinium, contribute likewise an almost equally considerable contingentwhile Bacteria in their characteristic motile and;quiescent states areinvariably present, and furnish an abundant and ever ready pabulum fortheir more highly organized animal consociates.The question presented to the author for solution was, from whencewere derived all these myriad organisms, frequently produced in such