INFUSORIAL ANIMALCULES. 



51 



The surrounding shell of the Melicerta is inflexible, and the soft and tender 

 animalcule can withdraw itself at pleasure within its protecting envelope. The 

 creature is exceedingly sensitive, and shrinks into the concealment of its case 

 upon the slightest motion of the water in which it lives. It is seen partially 

 withdrawn in figure 72, where the rotatory organs are seen closed up, and the 

 two eye-specks are detected at a a. The Melicerta is found upon the leaves of 

 duckweed and other water plants. Its size, when expanded, is one-twelfth of an 

 inch ; the length of the case one twenty-fourth ; and that of the eggs are one- 

 one hundred and fiftieth of an inch. 



Fig. 73. 



