XX MECHANICAL FUNCTIONS. 



so that the food which has been taken in by one of the 

 mouths, contributes to the general nourishment of the 

 whole mass of aggre- Fig. 14. 



gated polypi. These 

 curious facts were dis- 

 covered by Cuvier, 

 and are represented 

 by Fig. 14, where the 

 stomachs of the three 

 polypi, with their ten- 



tacula spread out, are seen communicating at their lower 

 extremities with a canal, which thus, becomes a common 

 stomach to the whole colony. 



INFUSORIA. 



46. The infusory insects, or infusoria, were so named 

 from the circumstance, that they always appear during the 

 warm seasons, in water in which vegetable or animal sub- 

 stances have been infused. Hence they exist in stagnant 

 ditches and pools of water, everywhere during the summer 

 and autumn. These animals are generally too minute to 

 be distinguished by the naked eye, and therefore it is to 

 microscopic observations that we owe our knowledge of 

 their existence and habits. 



47. Former writers on natural history, have called these 

 animalcula, monads, and have regarded them as occupying 

 the very lowest rank of animal creation. Some have even 

 expressed doubts whether they really belong to the animal 

 kingdom ; but would rather consider them as molecules, or 

 the elementary particles of organic beings, separated from 

 each other by chemical decomposition, but retaining the 

 power of voluntary motion. 



48. The infusoria, during the last century, have been 

 the object of very laborious microscopical research ; no 

 naturalist considering himself accomplished until he had 

 spent a considerable portion of time in observing the 

 motions and studying the characters of these animated 

 particles. Many theories, conjectures, and disputes, 



Whence do the infusoria derive their name ? What was the former 

 name for infusoria? 



