Untitled

F. DUJARDIN, 1841. T. VON SIEBOLD, 1845. 19consistence, although, through the superaddition of a denser externalmembrane, they were incapable of emitting thread- or root-like pseudopodicprocesses. No trace of a muscular or nervous system could bedetected by this authority, while the non-existence of the complex digestiveapparatus described by Ehrenberg was effectually demonstrated. Onfeeding Vorticellae and other animalcules with carmine, in accordance withthe plan adopted by Gleichen and Ehrenberg, Dujardin found that thefood-particles, after their reception at the oral aperture,were not retainedin definite and permanently fixed stomach-sacculi, but after aggregationinto small spheroidal masses were passed backwards into the body-sarcodeor parenchyma, and there freely circulated until digestion or rejection atthe anal aperture. The somewhat similar and characteristic independentcirculation of the inner sarcode or parenchyma of Paramecium bursariaand Vaginicola crystallina was also recorded for the first time by Dujardin.The contractile organ, first discovered by Spallanzani, and interpreted byEhrenberg as belonging to the reproductive system, was pronounced bythis investigator to be a mere vacuolar space situated close to the surface,apparently fulfilling a respiratory function by the continual absorption andexpulsion of water.This simple interpretation of the organization of the Infusoria arrivedat by Dujardin, in opposition to that of Ehrenberg, soon gained powerfuladherents. Among the more noteworthy authorities who also by theirindependent and almost contemporaneous researches, arrived at conclusionscoinciding with those of Dujardin and antagonistic to the polygastricand Focke. Thuret andtheory, may be mentioned the names of MeyenUnger, again, from a botanical point of view, indicated the close correspondenceof the zoospores of Ckara, Vaucheria, and various confervoid algaewith the monadiform animalcules referred by Ehrenberg to the generaChlamydomonas, Phacelomonas, and Microglena. The most decisive advancemade towards the elucidation of the true structure and affinities of the Infusoria,following upon Dujardin's investigations, was, however, accomplishedby Carl Theodor von Siebold. It was this biologist who, in his ' Text-bookof Comparative Anatomy/ published in the year 1845, first enunciated thetheory, anticipated to some extent by Oken, Schleiden and Schwann,that the representatives of the Infusoria were unicellular organisms. Eachseparate animalcule possessed, in his opinion, the value only of a simplecell, of which the central gland-like organ observed by so many previousauthorities, was now for the first time declared to be homologous with anordinary cell-nucleus, and described under a like distinctive title. Thecontractile spaces or vesicles were further interpreted by Siebold as possessinga circulatory or cardiac function. The simple sarcodic nature of the bodysubstanceof the Infusoria, first pointed out by Dujardin, was fully recognizedby this authority, and all the organisms possessing such a simpleunicellular structure were assembled together as the representatives ofan independent sub-kingdom of the Invertebrata, upon which he conferredC 2