INFUSORIAL ANIMALCULES. 41 



length, by the aid of which it is alternately extended and shortened. The ani- 

 malcule, at the approach of danger, coils up its tiny cable with the quickness of 

 thought, sinking down towards the spot where it is anchored ; and then again when 

 the peril is past, floats upwards in search of food, and swings once more to the 

 utmost extent of its line. This contractile action, as Mantell remarks, is contin- 

 ually going on now, in one or two individuals only, then in several, and often 

 the whole group suddenly shrinks down into a confused mass, and the next 

 instant expands, and every little bell becomes fully developed, with its cilia in 

 rapid oscillation. 



The group in the figure represent a number of animalcules, of this species, in 

 different attitudes and conditions. Some have their stalks stretched to the 

 utmost length, with their crowns of cilia in full action, while others have their 

 stems more or less coiled. Many are single, and others (a a a,) have divided 

 into two, and the stems of several are seen, from which the animalcules have 

 broken and swam away. The length of the body of this species varies from one- 

 two hundred and eightieth of an inch to one-five hundred and seventieth. 



The self-division of these Infusoria proceeds as follows : The bell first begins 

 to expand in breadth, and then a separation commences extending in the direc- 

 tion of its length, double rows of cilia becoming meanwhile formed. At length, 

 the two parts being perfectly developed, the bell divides into two animalcules, and 

 fringes of cilia next appear encircling the base of each. Soon the young animal- 

 cules twist off from the stem which speedily decays, and after swimming about 

 for some time, at last put forth a new stem from the end of each bell ; then fix- 

 ing themselves to some object, they multiply by self-division, and become in 

 their turn the progenitors of a numerous race. 



In figure 50, two bell-shaped animalcules are seen, which Fig - 5( j > 



have just been produced from one by separation, each being 

 still attached to the parent-stem by its own stalk. 



The advantage resulting from the use of a colored 

 fluid, in enabling the observer to detect the stomach-cells 

 of minute Infusoria, has already been mentioned more than 

 once ; but the following detail of its employment by Dr. 

 Mantell, when experimenting upon Bell-shaped Infusoria, 

 is too instructive to be omitted. " I place," says this inter- 

 esting writer, "a drop of a solution of carmine in the water between the 

 plates of glass containing these animalcules ; the fluid in which they are 

 floating now appears turbid, and full of gray particles, which are thrown into 

 rapid motion by the vibrations of the cilia, and currents are seen passing 

 to and fro from the mouths of the animalcules. In a few minutes the 

 water gradually becomes clear, and several round spots of carmine are 

 apparent in the body of each animalcule. We have, in fact, caused their 

 little stomachs to be filled with coloring matter, and can now distinguish their 

 number and arrangement. If the body of the animalcule were a mere cavity, it 

 is obvious that the carmine must have collected into a single ball or mass ; but 



