66 A HALF-HOUR WITH THE 



The mouth of their little cup is surrounded by cilia, 

 which are in constant movement j and when ex- 

 amined minutely, they will be found to possess two 

 apertures, through one of which currents of water 

 pass into the body, and from the other pass out. 

 Not unfrequently the cup breaks off its stalk. It 

 then contracts its mouth, and proceeds to roll about 

 free in the water. Many other curious changes in 

 form and condition have been observed in these 

 wonderful bell-shaped animalcules. 



If, now, we go to a very dirty pond indeed, into 

 which cesspools are emptied, and dead dogs and 

 cats are thrown, we shall find abundant employ- 

 ment for our Microscope in the beautiful forms of 

 animalcules which are placed by the Creator in 

 these positions to clear away the dirt and filth, and 

 prevent its destroying the life of higher animals. 

 In such waters, amongst a host of minor forms, we 

 are almost sure to meet with the magnificent Para- 

 mcecium Aurelia, figured at 39, plate 2. He moves 

 about the water a king amongst the smaller prey, 

 on whom he feeds without ceasing. He is of an 

 oblong form, covered all over with cilia, and very 

 rapid and active in his movements, as able to dart 

 backwards as forwards, and turning round with the 

 greatest facility. In his inside several spots are 

 observed. If a little indigo or carmine is intro- 

 duced into the water in which he lives, these spots 

 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 



