Prof. Ehrenberg's Researches on the Infusoria. 209 



vations with improved instruments. And finally, on his late 

 journey with Baron Alexander Humboldt into the vast steppes 

 of Siberia, even to the frontiers of China, and of the plateau of 

 Tartary, notwithstanding the extreme rapidity of his progress, 

 he made this highly interesting branch of zoography a principal 

 object of investigation. The entire reformation which these re- 

 searches have made in the classification of infusory animals, 

 will be shewn under our third division. But as a necessary 

 preliminary, and as constituting the most valuable part of Dr 

 Ehrenberg's discoveries, we must give some account of the 



II. Organization of the Iifusoria. 



Before entering into the detail of the individual systems, it 

 will be well to state briefly the method of observation employed 

 for their development. 



This consists in nothing else than furnishing the Infusoria 

 with organic colouring matter for nutriment. Simple as this 

 may appear, it was not till after ten years' observations that Dr 

 Ehrenberg succeeded in selecting the fittest substances, and in 

 applying them in the manner best adapted for the satisfactory 

 exhibition of the phenomena. Trembley and Gleichen long 

 ago had recourse to this method for the elucidation of the armed 

 hydrge, but without consequences of much importance for the 

 structure of these animals. The cause of the repeated failure 

 of all these attempts, arose from the employment of metallic and 

 earthy colouring substances, or such as had been submitted to 

 boiling in the preparation. These were found either to kill the 

 animals, or to be unfitted as articles of nutriment. Equally 

 unsuccessful were some attempts made with the indigo and lack 

 of commerce, which were found always to contain a greater or 

 less proportion of white lead. It was not till he used pure 

 indigo, that these experiments succeeded in a desirable man- 

 ner. Immediately on a minute particle of a highly attenuated 

 solution of this substance being applied to a drop of water con- 

 taining some of the pedunculated vorticellae (which are most 

 adapted for the first observation), and placed under the object 

 glass of tlie microscope, the most beautiful phenomena present 

 themselves to the eye. Currents are excited in all directions by 

 the rapid motion of the ciliae, which form a crown round the 



