1 8 BIBLIOGRAPHY. 



proof in these latter instances was brought forward ; the coloured eye-like 

 pigment specks conspicuous in Euglena, Ophryoglena, and various other 

 types, were finally regarded by him as highly differentiated visual organs. 



Ehrenberg's evidence in support of his many-stomached or polygastric 

 theory was built on too insecure a foundation to stand the test of contem- 

 porary investigation, and before which, indeed, the entire superstructure 

 of his most ingeniously conceived digestive, neural, haemal, and repro- 

 ductive systems was speedily demolished. 



The first and most prominent authority to call in question the accuracy 

 of Ehrenberg's interpretations was M. Felix Dujardin, who, firstly in various 

 contributions to the ' Annales des Sciences Naturelles,' extending through 

 the years 1835-38, and later in a special treatise devoted to this subject, 

 ' Histoire Naturelle des Infusoires,' 1841, brought forward evidence that 

 threw an entirely new light on the organization of the members of this 

 group. Through an investigation, in their living state, of various representa- 

 tives of the minute marine shell-forming organisms upon which D'Orbigny, 

 in the year 1826, conferred the distinctive title of Foraminifera, Dujardin 

 discovered that their internal structure was far more simple than had been 

 previously conjectured. Guided only by an acquaintance with the empty 

 shells or tests of these minute beings, and taking into account their 

 predominating nautiloid form and chambered character, D'Orbigny and 

 his contemporaries concluded that their fabricators exhibited a correspond- 

 ingly high degree of organization, and described them as diminutive 

 representatives of the Cephalopodous order of the Mollusca. Dujardin, 

 examining various Mediterranean forms belonging chiefly to the genera 

 Cristellaria, Miliola, and Vorticialis, speedily determined that their living 

 occupants could lay claim to no such exalted position, being found by him 

 to possess no distinct organs or differentiated tissues, but in their place 

 a simple transparent gelatinous body, capable of extending fine thread- 

 like prolongations of its substance in every direction, by means of which 

 they adhered to and crept over submerged objects. Dujardin likewise 

 discovered in both salt and fresh water minute organisms possessing 

 similarly extensile gelatinous bodies and still more simple, unchambered, 

 and mostly corneous tests, upon which he conferred the generic names 

 of Gromia and Eugtyphia. Between these several types and Ehrenberg's 

 test-inhabiting polygastric genera Arcella and Difflugia, and the still more 

 simple shell-less Amcebce, Dujardin soon recognized that there subsisted the 

 closest affinity, and separating them from all other forms, instituted for 

 their reception, in reference to their peculiar mode of locomotion by root- 

 like extensions of their body-substance, the class title of the Rhizopoda. 

 Dujardin further conferred upon the plastic, gelatinous, and apparently 

 homogeneous body-substance of these Rhizopoda the distinctive name of 

 "sarcode," and finally sought to demonstrate that in all those infusorial 

 forms described by Ehrcnberg as exhibiting a polygastric type of structure, 

 their body-substance possessed a similar simple gelatinous or sarcode 



