History of the Hairy -backed Animalcules. 389 



genera, which have no real affinity with them, his system of 

 arrangement being artificial, and therefore, necessarily, in some 

 cases, unnatural.* 



M. Dujardin, in 1841, described another species, which he 

 named Gh.squammahis, and rejecting Ehrenberg' s arrangement, 

 united the then known forms with others, with which they have 

 no more affinity, and placed the heterogeneous group among the 

 Infusory animalcules by the name of Symmetrical Infusoria. 

 His ground for the change is thus expressed : — " The Ichthy- 

 dina, according to M. Ehrenberg, ought to have a rotatory 

 organ, simple, continuous, with an entire margin ; but, in fact, 

 the vibratile cilia of the ventral surface of the Chastonotes do 

 not at all constitute a rotatory organ. "f 



Ten years later, the same zoologist described another form 

 (Plate ii. Fig. 16) under the title of Ecliinodera } % apparently 

 allied to the same group ; to which, however, he now assigned 

 a higher place, viz., intermediate between Crustacea and 

 Yermes. He believes that this is " a type differing from the 

 Helminthes acanthocephales, the Systolides [Rotifera], the HJnto- 

 mostraca Gopepoda [Cyclops, etc.] and the Sipuncles, yet at the 

 same time offering points of resemblance to each of these. It 

 is a sort of Gopepode without feet, with the mouth of a Sipun- 

 cuius, and the neck of an Echinorhynchus, and a muscular 

 oesophagus like those of the Systolides, the Tardigrades, and 

 the Nematoid Helminthes." 



M. Perty§ and Herr Yogt|| concur in the exclusion of the 

 Ghcetonotidce from the Rotifera ; the former, however, has not 

 ventured to assign them any definite position, while the latter 

 associates them with the Planarioid worms (Turbellaria). 



* It is the fashion to depreciate and decry Ehrenberg. I have no sympathy 

 with those who, taking their stand upon the ground which be has cleared with 

 incredible labour and genius, can assume airs of pity or contempt when they dis- 

 cern inconsistencies or defects in his system. Many years' study of the Rotifera 

 has enabled me in some measure to appreciate the gigantic labours of the Prussian 

 microscopist, and to compare them with those of his successors and criiirs. I 

 take, for example, Dujardin's Hist, des Infusoires, and have no hesitation in 

 asserting that this work does not manifest one-fourth part of the renl actual 

 acquaintance with the subjects treated, that is possessed by Ehrenberg' s great 

 work. Corrections and improvements in some points cannot fail to be pointed 

 out by those who begin where the Prussian left off; and the advance of science, 

 and the improvement of the microscope itself, have, ot course, made antiquated 

 and displaced many of his statements and conclusions; but, looking at microscopic 

 zoology as it was when Ehrenberg took it up, and as it was when he laid it down, 

 I think it not too much to say that he stands in the foremost ranks of the scientific 

 army, side by side with such names as Aristotle, Linnams, and Cuvier, and that 

 his Die Infusionsthierchen is a monument to his fame, cere perennius, and such as 

 few indeed have been able to erect. 



f Hist, des Infus., p. 569. 



% Annal. d. Sci. Nat. 1851. The name is erroneously spelled " Ellimoderia" 

 in the 4th Ed. of Pritchard's Infusoria, p. 380. 



§ Zur Kenntniss Meinster Lebem formen. 



|| Zoologisehe Briefe. 



