PBOTOPHTTES. 27 



invested with a strong envelope, and pass into the still state from which they had 

 previously emerged. This process is continually repeated and causes the plant to 

 multiply with great rapidity. 



A class of protophytes, which are termed Diatomaceae, probably from the readi- 

 ness with which they are cut or broken through, are distinguished for the delicate 

 shell of flinty matter which encloses the membranes of the cell. 



As the protophytes afford beautiful objects for the microscope, we shall present 

 some of the most interesting forms, and their various modes of aggregation, before 

 proceeding to describe the peculiarities of many of the more curious animalcules. 

 We begin with the monads. 



MONADS. These are the smallest of all organisms, which the wonderful power of 

 the microscope has revealed to us. So minute are they, that they must be magni- 

 fied 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, moving 

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

 but the greater part are colorless. All are possessed of one or more of the thread- 

 appendages termed cilia. The monads vary in size, from one-twenty-four-thou- 

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



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

 in which each individual, 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 organism is globular in form, and presents a glassy 

 appearance. It is found in water containing animal matter; but as the animal 

 substance decomposes the monads unite, forming colorless jelly-like masses, con- 

 sisting of infinite multitudes of their bodies, which are seen with the naked eye 

 rising and floating upon the surface of the water. This atom is furnished with only 

 a single organ of motion ; a delicate cilium issuing from one end, 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 owe 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 structures in their full dimensions, and 

 exceeds in bulk thirteen thousand millions of the smallest size. The conception of 

 such minuteness is beyond the grasp of our mind ; yet each, an organized structure, is 

 not too small to claim and receive the regard of Him who called into life and am- 

 ply endowed it with peculiar organs and properties, adapted to the mode and range 

 of its existence. 



G-RAPE MONAD. The grape monad is so called from the circumstance that the 

 individuals at times unite and form clusters, like bunches of grapes or 

 berries. A natural group of these protophytes is shown in figure 

 9, where they are magnified linearly three hundred and fifty times ; 

 the diameter of the cluster being one four-hundred-and-thirtieth 

 part of an inch, and that of each individual one twenty-three-hun- 

 dredth of an inch. 



