30G ORGANS OF DrQESTION. 



other animalcules with their internal sacs filled with this 

 coloured matter ; the same was done by Trembley ; and 

 these stomachs are figured by Miiller, Bruguiere, and most 

 others ; but Miiller supposed that they fed upon water, from 

 their stomachs being most frequently filled with that fluid. 

 Ehrenberg has more extensively employed opaque colouring 

 matter to detect the forms of these internal cavities, and by 

 using principally carmine, sap-green, and indigo, carefully 

 freed from all impurities which might prevent their being 

 swallowed, he has succeeded better than his predecessors in 

 unfolding the structure of the digestive organs of animal- 

 cules. Such coloured organic matter, diifused as fine 

 particles mechanically suspended in the water in which 

 animalcules are placed, is readily swallowed by them, and 

 renders visible, through their transparent bodies, the form 

 and disposition of their alimentary cavities; but, how- 

 ever long they remain in these coloured infusions with their 

 stomachs distended with the colouring matter, it is not 

 perceived to communicate the slightest tinge to the general 

 cellular tissue of their body. They appear to possess an 

 acute sense of taste in rejecting coloured metallic and other 

 substances which might prove hurtful to them, and their food 

 appears to consist chiefly of smaller animals of the same 

 class and of particles of mucus or other decomposed organic 

 matter found in the water. 



In most of the polygastric animalcules there is an ali- 

 mentary canal, with an oral and an anal orifice, which 

 traverses the body, and is provided with numerous small 

 round coecal appendices, which open into its parietes 

 throughout its whole course, and which appear to perform 

 the office of stomachs in receiving and preparing the food. 

 In the simplest forms of animalcules, however, as in the 

 monas atomus (Fig. 107- A.), there is but one general 

 orifice (107. A. b.) to the alimentary cavities (107. A. d.) 9 

 which is placed at the anterior extremity of the body and is 

 surrounded with long vibratile cilia (10J. A. ,) which serve 

 both as organs of motion and tentacula. The several 

 stomachs (A. d.) covered by the general wide integu- 

 ment, (A. e.) open by distinct short cesophageal canals 

 (A. c.) into the common buccal orifice (A. #.), and 

 there is no separate anal aperture for the excrementi- 



