20 BIBLIOGRAPHY. 



the suggestive title of the Protozoa. These Protozoa Siebold further 

 divided into the two subordinate classes of the Rhizopoda and Infusoria, 

 the former corresponding with the same section as similarly named by 

 Dujardin, and including all those forms whose locomotion was accomplished 

 by the extension of lobate or filiform processes or pseudopodia, while the 

 latter embraced those in which cilia or flagelliform appendages fulfilled 

 a similar function. The distinction between the Ciliate and Flagellate 

 sections of the Infusoria was also fully recognized by this investigator, who, 

 however, conferred upon them titles differing from those now recognized. 

 The Ciliata only being regarded by him as possessing a distinct oral 

 aperture, were denominated the " Stomatoda," and the supposed entirely 

 mouthlcss flagellate animalcules, the " Astomata." Siebold, by his creation 

 of the sub-kingdom Protozoa, acceptation of the Infusoria as simple 

 sarcode organisms possessing individually the morphological value of a 

 simple cell, and restriction of the Infusoria to the Ciliate and Flagellate 

 members of the Protozoa, practically initiated that definition of the boun- 

 daries and organization of the class that receives the most powerful support 

 at the present day, and is closely adhered to by the present author. 



As might be anticipated, a universal concession to Siebold's unicellular 

 interpretation of infusorial organization was by no means granted at the 

 period of its announcement to the scientific world. Although the polygastric 

 hypothesis, in the sense rendered by Ehrenberg, was speedily rejected, 

 there have not been wanting those who from that earlier date up to the 

 present time have sought to associate with these microscopic beings a 

 complex type of structure, and to demonstrate their affinities with many of 

 the more highly organized invertebrate sub-kingdoms. Among the first 

 opponents of Siebold in this direction the names of Eckard and Oscar 

 Schmidt are the most prominent. Both founded their arguments against 

 the unicellular theory partly from their independent observation of the 

 development of embryos from within the interior of the body-substance of 

 Stentor ccertUeiis and polymorpJuts, while the latter more especially sought 

 to demonstrate the close affinity of the higher ciliate animalcules with the 

 Turbellarian group of the sub-kingdom Annuloida. O. Schmidt's indication 

 of this supposed affinity was brought about by his discovery in Paramecium 

 aurclia and Bitrsaria {^PanopJirys^ flavicans of a subcuticular layer of minute 

 rod-like bodies — now familiarly known (as trichocysts) to be developed in 

 many infusorial forms — similar to those met with in various Turbellaria 

 and lower Annclides. He further discovered that the contractile vesicle in 

 various animalcules communicated with the outer water, a fact which at 

 once suggested to his mind the probable correspondence of this structure 

 with the water-vascular system of the last-named higher zoological groups. 

 These results of O. Schmidt's researches bring us to the year 1849, 

 a date memorable for the appearance on the field of that accom- 

 plished investigator to whom we are most indebted for our present 

 knowledge of the morphology and development of the infusorial animal- 



