136 AQUATIC MICROSCOPY FOR BEGINNERS. 



The' general opinion is that "animalcules" have no 

 color. This is a mistake. The majority are almost 

 colorless, but green, crimson, yellow, indigo-blue or 

 almost black Infusoria are not uncommon, and the 

 loricae, as stated, often become brown with age. 



The free-swimming Infusoria are more abundant 

 than the attached ones, and. much more difficult to ex- 

 amine because they will never stand still. But how 

 do these creatures, all of which are invisible without the 

 microscope — how do they move ? For this purpose 

 they have organs of two kinds, and they are 

 separated into two great classes according as they 

 possess the one kind or the other. In some there are 

 one or more long, colorless lashes which extend from 

 the front of the body, beat against the water, and so 

 row the animal about with great rapidity. Each of 

 these lashes is called 2.flagellum (plural flagelld). In 

 others there are on the body short, fine hairs, which 

 are continually vibrating so rapidly that they are often 

 invisible even under a high power objective. The 

 short hairs are called cilia and it is their action on the 

 water that urges the animal about even more quickly 

 than that of the flagella. The cilia may be confined 

 to a circle around one end of the body, or they may be 

 on the lower surface only, or the entire animal may be 

 covered with them. Infusoria with cilia are more 

 numerous than Infusoria with flagella. They are^ 

 however, not the only ciliated animals. The Rotifers 

 are well supplied, and certain small aquatic worms 

 have the entire body ciliated. 



Although the Infusoria are so abundant that scarcely 

 a drop from any pond or ditch can be examined with- 

 out exhibiting some, the beginner will, I fear, have 



