CHAPTER I. 



Branch I. — Protozoa (Animalcules, Infusoria, Monads, 



etc. ). 



General Characters of Protozoans.— Few of the 



Protozoans can be seen without the aid of the microscope; 

 they are microscopic animals or animalcules. One of the 

 simplest forms is a very minute being called Amoeba. It is 

 to be sought for in standing pools, where it lives on the 

 leaves or stems of submerged plants or in the mud or ooze 

 at the bottom. Taking up a drop of water from the bot- 

 tom of such a pond and placing it under high powers of 

 the microscope, we may, after close examination, detect a 

 very small moving mass of jelly-like substance or proto- 

 plasm. As it glides over the glass the sides of its body 

 bulge out, or it suddenly throws out lobes or projections 

 from various parts of its body as if it were falling apart; 

 then it retracts these transparent root-like processes, which 

 are called pseudopodia, or false feet, and becomes smooth 

 and rounded, like a drop of thick syrup. Throughout the 

 body-mass are granules which have a rude sort of circula- 

 tion. There is also in or near the middle a clear round 

 body called the nucleus. In all respects the Amoeba is a 

 cell, i.e., a bit of protoplasm with a nucleus in the middle. 

 Besides the nucleus, a clear, hollow, round, pinkish space 

 which enlarges and contracts is usually present. This is 

 called the " contractile vesicle." 



The food of the Amoeba consists of one-celled plants 



