$^0 Zoologif. 



Phytozoology : 2d, The Organisation of Infusory Animal- 

 cules : 3d, Their Classification : 4th, Their Geographical 

 -Distribution. 



In the historical part, appraisements of the respective 

 labours of Mliller, Nitsch, Schrank, Treviranus, Dutrochet, 

 Oken, Lamarck, Cuvier, Corti, Savigny, Schweigger, Losano, 

 Bory de St. Vincent, Baer, and Goldfuss occur. 



The remarks on organisation are introduced by a notice 

 of Dr. Ehrenberg's method of observation. He supplied 

 the Infusoria with organic colouring matter for nutriment. 

 Although this had been done by Trembley and Gleichen 

 before him, it was not till after ten years' observations that 

 Dr. Ehrenberg succeeded in selecting the fittest substances, 

 and in applying them in the best manner. The repeated 

 failure of so many 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 be unfit as articles of nutriment. 

 Equally unsuccessful were some attempts made with the indigo 

 and lac 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 his experiments succeeded in a desir- 

 able manner. It is requisite in these experiments to employ 

 colouring matter which does not chemically combine with 

 water, but is only diffused in a state of very minute division. 

 Indigo, carmine, and sap green, are three substances which 

 answer very well the necessary conditions, and are easily 

 recognised by the microscope. But, whatever substance is 

 used, we must be very particular that it contains no lead ; an 

 impurity which very frequently enters into the colours of 

 commerce. It is well, before applying any coloured solution 

 to the drop of fluid under the field of the microscope, to take 

 a general survey of the species which we may expect to find 

 in the drop under examination. Immediately on a minute 

 particle of highly attenuated solution of indigo being applied 

 to a drop of water containing some of the pedunculated Vor- 

 ticellse (which are fittest for the first observation), the most 

 beautiful phenomena present themselves to the eye. Currents 

 are excited in all directions by the rapid motion of the cilia&, 

 which form a crown round the anterior part of the animal- 

 cule's body, and indicated by the movements of the particles 

 of indigo in a state of very minute division in different direc- 

 tions, and generally all converging towards the orifice or 

 mouth of the animal, situated, not in the centre of the crown 

 of ciliae, but between the two rows of these organs which 

 exist concentric to one another. The attention is no sooner 



