206 Dr Gairdner's Analysis of 



participate the ideas of Treviranus, the last champion of the 

 generatio spontanea, on their mode of development. 



The systematologists Lamarck and Cuvier only altered by 

 divisions and subdivisions the arrangement of the already deter- 

 mined species, but did not add to the existing stock of facts. 

 They even, in some measure, contributed to retrograde the 

 science by the propagation of the errors into which Muller fell 

 from his ignorance of the organization of these animals. The 

 former even declared the ova to be gemmules, although Corti 

 had long before described and figured the exclusion of the young 

 from the ovum. 



A more important accession was made by Professor Nitsch 

 of Halle, the most important by far of any which exist from 

 the time of Muller down to Dr Ehrenberg. His researches 

 were principally directed to the genera Cercaria and Bac'illaria. 

 He rendered much more probable in the former the existence 

 of a mouth and intestinal canal, and in the Cercaria viridis re- 

 cognises distinctly the presence of eyes. This meritorious na- 

 turalist also divided this genus, as, left by Miiller, into twelve 

 others from his own observations. In 1824, he compares the 

 structure of the genus Brachioniis to that of the Entomostraci, 

 which, although it differs entirely from Savigny's observations, 

 is much nearer the truth. 



Schweigger of Konigsberg, in 1820, communicated some in- 

 teresting observations on these animals ; and formed an indus- 

 trious recapitulation of all that had been done up to his time. 

 Even at this late date, we find him stating at p. 245 of his 

 Handbucli der Naturgeschiclite der Skeletlozen Thiere, that 

 " the infusoria consist of mere gelatine, without any internal 

 organ. Their nutrition can be carried on in no other way than 

 by the surface. The same mode of nutrition has even been 

 pointed out in the Iirfasoria vasculosa, without being limited 

 to them. In some, (for example the Cercaria) Nitsch saw 

 oval suction," &c. And again, on the subject of their propaga- 

 tion, he observes, p. 249, " All increase of the infusoria seems 

 to result from the spontaneous separation either of their exter- 

 nal parts, as in the Paramoeciae and Bacillariae, or of their inter- 

 nal substance, as in the Vibrio and Volvox,"" which shews how 

 indistinct was his conception of these two last genera. 



