PRACTICAL ZOOLOGY 



Chapter I. 



THE PROTOZOA. 



peotozoon is an animal which consists of a single nucleated 

 )rotoplasmic mass which may be compared to a single cell 

 >f the tissues of a higher animal. 



Protozoa are always of small size, and are usually micro- 

 ;opic. 



I. AMCEBA PROTEUS. 

 This protozoon is found in rivers and in freshwater pools, 

 imong algae known as ' diatoms ' and ' desmids,' and in damp 

 situations. Other amoebae may be obtained from soil or by 

 laking a hay-infusion in pond water and skimming off the 

 iridescent pellicle that accumulates after four weeks' culture, 

 [ts indefinite and ever-changing shape is characteristic, and 

 las gained for it the name * proteus animalcule.' There are 

 several forms, the largest of which are just visible to the naked 

 sye, while others are exceedingly minute. 



Place a drop of water containing Amcebcs on a slide ; 

 :over ; and search for the animals with a low power of the 

 licroscope. When found, examine them with a high power. 



l. General Appearance. 



The animal is an irregular mass of protoplasm, running 

 >ut into blunt processes or pseudopodia, the protrusion and 

 fraction of which cause great changes in the form of the 

 ill. The pseudopodia may branch slightly. 



Structure. 



The whole body is a naked mass of protoplasm, of which 

 two portions are distinguishable. 

 1. The ectosarc is the clearer outer portion of the body. 



