EHRENBERG, 1836. I 7 



Notwithstanding the comparative imperfection of the optical appliances 

 at his disposal, it may indeed with justice be said that Ehrenberg's 

 figures, so far as they relate to contour and broad superficial details of 

 structure, are scarcely to be improved upon, and considerably excel, in 

 execution, the delineation of the same forms included in many more 

 modern treatises. Ehrenberg, like Muller, associated together under the 

 collective title of the Infusoria a vast assemblage of minute animal and 

 vegetable organisms, a small section only of which finds its equivalent under 

 the same classificatory term in its more modern and restricted sense. In 

 addition to the true Infusoria he still retained the Rotifera, or wheel- 

 animalcules, the descriptions and illustrations of these monopolizing over 

 one-third of the text and plates of his entire volume, while a very con- 

 siderable portion of the remainder is occupied with the description and 

 delineation of the essentially vegetable Desmidiaceae and Diatomaceae, to 

 which are also added many forms of Rhizopoda and unicellular plants 

 other than the Bacillaria. 



It was to the residual portion, that alone coincides with the tribe Infu- 

 soria as at present recognized, that Ehrenberg attributed the possession 

 of a highly complex internal structure, whose chief feature was further 

 described as consisting of a large number of pedunculate bubble-like 

 stomach-cavities associated with one another in a clustered form. The most 

 weighty testimony relied on by Ehrenberg in support of this theory was 

 derived from his repetition and extension of the experiments of Gleichen, 

 by whom it was demonstrated that carmine, indigo, or other pigmentary 

 matter suspended in the water was freely devoured. After passing through 

 the oral aperture this coloured matter was found to become collected in 

 small spherical bubble-like masses, variously distributed throughout the 

 body-substance or parenchyma, and without apparently taking the pains 

 to assure himself that these vacuoles occupied a permanently fixed 

 position, Ehrenberg assumed that such was the case, and assigned to 

 each vacuole the significance of a distinct food-receptacle or stomach ; it 

 was with special reference to these supposed numerous stomach-cavities 

 that the title of the Polygastrica was adopted by him for the dis- 

 tinction of this particular group. Ehrenberg's conception of the high and 

 complex organization of his so-called Polygastrica, however, by no means 

 ended here. The transparent vacuole possessing the property of contracting 

 rhythmically, first observed by Spallanzani, conjointly with the still more 

 universally recognized gland-like nucleus or endoplast, were pronounced to 

 be integral parts of the male generative organs, the former representing a 

 seminal vesicle, and the latter a seminal gland or testis. The minute 

 granular corpuscles distributed more or less abundantly throughout the 

 substance of the body were declared to be eggs, which after fecundation 

 from the seminal vesicle were discharged through the anal aperture or 

 vent. The possession by these Polygastrica of a complex muscular, 

 nervous, and blood-circulating system was likewise insisted on, though no 



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