INFUSORIAL ANIMALCULES. 27 



color, and the line of division between the red and blue water was clearly 

 defined. Upon close examination in a glass, the water assumed a pale red tint, 

 and when viewed by the microscope was found crowded with animalcules one- 

 thousandth of an inch long, of an oval shape, and encircled at the middle with 

 a ring of cilia. They were beheld darting about in all directions and exploding, 

 their bodies bursting to pieces in a few seconds after their rapid motions had 

 ceased. A stratum of red water, twenty-four miles long and seven broad, is 

 mentioned by Dr. -Pceppig, as occurring near Cape Pilares. When beheld from 

 the mast-head it appeared of a dark red hue, but as the vessel advanced on her 

 course it changed into a brilliant purple, while a rosy tint illumined the track 

 of the keel. This water was perfectly transparent, but small red specks could 

 be perceived moving through it in spiral lines. 



Having thus briefly discussed the nature, structure, and habits of Infusoria, 

 we will now proceed to describe, particularly, some of the more interesting 

 species. 



POLYGASTRIC ANIMALCULES. 



MONADS. These are the smallest of all living creatures, which the wonderful 

 power of the microscope has revealed to us. So minute are they, that they must be 

 magnified linearly 300 times in order to be seen at all, and 500 times if we wish to 

 observe them accurately. They appear as transparent globular or oval bodies, mov- 

 ing rapidly about in all directions. Some are of a red hue, others green, many yel- 

 low, but the greater part are colorless. All are possessed of one or more organs 

 of motion. Many are destitute of eyes, but in others a bright red eye has been 

 detected. The individuals of this family of Infusoria vary in size, from one- 

 twenty-four-thousandth of an inch in length, to one-forty-thousandth of an inch. 



TWILIGHT MONAD. In figure 8, is shown a group of twilight monads, Fi s- 8 - 

 in which each creature, although exhibited as a mere point, is magnified in 

 length and breadth 800 times, and the space it occupies upon the paper is 

 640,000 times greater than that which it actually covered in the fluid in 

 which it lived. This animalcule is globular in form, and presents a glassy appear- 

 ance. It is found in water containing animal matter, upon which it feeds ; but as the 

 animal substance decomposes the monads die, and colorless jelly-like masses, consist- 

 ing of infinite multitudes of their bodies, are seen with the naked eye rising and 

 floating upon the surface of the water. This creature is furnished with only a single 

 organ of motion ; a delicate cilium issuing from its mouth, and by the aid of this 

 member it proceeds through the water, with considerable rapidity. The twilight 

 monad is only the twenty-four-thousandth of an inch long, but it sometimes, 

 though seldom, attains the length of one-twelve-thousandth of an inch, which it 

 never surpasses. A single shot, one-tenth of an inch in diameter, occupies more 

 space, than seventeen hundred millions of these living atoms, in their full dimen- 

 sions, and exceeds in bulk thirteen thousand millions of the smallest size. The 



