MICROSCOPE IN FRESH WATER. 47 



become coloured by his taking up these substances. 

 From this, Ehrenberg concluded that these spots 

 were stomachs, and as such spots are very common 

 amongst these animalcules, he called them many- 

 stomached (Polygastrica). There is, however, 

 reason to doubt the correctness of this conclusion 

 of the great microscopist, as, although these spots 

 exist in the body, they are not necessarily stomachs. 

 They are, in fact, empty spaces, or vacuoles in the 

 interior of the little lump of sarcode of which the 

 animal is composed. They are found in the vorti- 

 cella, and in most of the animalcules. 



All animalcules have been called infusory, be- 

 cause they seern so abundant in all kinds of vege- 

 table infusions. Ehrenberg divided them, into 

 Poly gastric and Rotifer ous. The last are also called 

 wheel-animalcules, as, when looked at through the 

 Microscope, they appear to be supplied with little 

 wheels on the upper part of their body. The most 

 common form of these creatures is the Rotifer 

 vulgaris (Fig. 36, PL 2). The branches or leaves of 

 any of our common water-plants can scarcely be 

 examined without some of those pretty little crea- 

 tures being found nestling upon them. The struc- 

 ture of this creature is highly complicated, and the 

 family to which it belongs is far removed from the 

 polygastric animalcules with which it is often asso- 

 ciated. On examination, the wheels will be found 

 to consist of two extended lobes, the edges of 

 which are covered with cilia. These cilia are in a 

 constant state of movement, and produce the ap- 

 pearance of wheels moving on an axis. Between 

 the wheels is the entrance to the mouth, which, in 

 many species of wheel-animalcules, is furnished with 

 a strong pair of jaws. This leads to an oesophagus, 

 a stomach, and an intestinal tube. Two little spots 

 on the neck seem to indicate the existence of eyes ; 



