SECTION I. 



psd 



THE GENERAL STRUCTURE AND PHYSIOLOGY 

 OF ANIMALS 



1. AMCEBA. 



IF we examine under the microscope a drop of water containing 

 some of the slimy deposit which collects at the bottom of pools of 

 rain-water and in similar situations, we occasionally find it to 

 abound in microscopic life ; and among the minute moving creatures 

 in such a drop we frequently find examples of a remarkable or- 

 ganism the Amceba or Proteus Animalcule (Fig. 1). This is 



a little particle of irregular 

 shape, which we should be 

 likely, on a cursory examina- 

 tion, to put down as motion- 

 less ; it appears somewhat like 

 an irregular particle of some 

 colourless glass-like substance 

 with a more granular central 

 portion. If, however, we make 

 an exact drawing of the out- 

 line of the Amoeba, and, after 

 an interval, compare the draw- 

 ing with the original, we find 

 that the drawing appears no 

 longer to represent what we 

 see ; a change has taken place 

 in the shape of the Amoeba ; 

 and careful observation shows that this change is constantly going 

 on : the Amoeba is constantly varying in shape. This change is 

 effected by the pushing out of projections or processes, called 

 pseudopods (psd.), which undergo various alterations of size 

 and shape, and may become withdrawn, other similar processes 

 being developed in their place. At the same time careful 



FIG. 1. Amoeba proteus, a living specimen. 

 c. rac. contractile vacuole ; mi. nucleus; 

 psd. pseudopods. (From Parker's Biology, 

 after Gruber.) 



