Prof. Ehrenbergs Researches on the Irifusoria 205 



systematic division, but only enumerates these important cha- 

 racters as collateral circumstances in his detailed description of 

 each species. We are certainly astonished that such important 

 glimpses escaped the acuteness of the Danish naturalist ; his 

 work, however, is posthumous, and we cannot help thinking, 

 that if he had lived to prosecute his investigations, Dr Ehren- 

 berg would have been anticipated in his discoveries. As it is, 

 Miiller takes the differences of the external organs as the bases 

 of his division, and, in consequence, associates in the same ge- 

 nus, species far removed from each other. He unites, for ex- 

 ample, in the genus Vortkella, the complicated forms of the 

 Furcularia and Rotatoria, with the much simple forms which are 

 supported on a spiral peduncle. Similar examples are furnish- 

 ed by the genera Paramoccium, Kolpoda, and Cercaria, the last 

 of which alone Nitsch, in the year 1816, divided into 12 distinct 

 genera. The genus Vibj-io comprises not only the aceti and 

 JluviatiUs, in which he describes an intestine and viviparous 

 generation, but also the simple bacillus, in which he could not 

 detect a single organ, and scarcely a trace of life. The same 

 observations apply to the genus Trichoda, and many others. 



Such was the state in which the science was left by Miiller, 

 furnished with a rich store of materials, and not a few valuable 

 hints to direct the path of later inquirers. 



Schrank, the Bavarian, was the first who made any important 

 additions to our knowledge of infusory animals after the death 

 of Miiller. He described in the Fcnina Boica 18 new species, 

 but he still took the external form as the basis of his division, 

 and seems to have been quite unacquainted with their structure 

 and mode of development. 



We may pass over Treviranus and Dutrochet, who treated 

 the subject more in an ideal manner — examining their relations 

 to other living forms — than by adding any thing new to what the 

 science already possessed. 



The warm fancy of Oken in 1805, revived in part the idea 

 of Buffon, in regarding the infusoria as the primitive materials 

 of all organic bodies, both animal and vegetable ; and that 

 growth is nothing but an increase to the already existing mass 

 of animalcules, which constitute the animal body. He does not 



