36 THE STORY OF ANIMAL LIFE 



thick gum. The movement may be traced by the 

 change in outline of the cell and by the change 

 in position of any granules that it may have taken 

 in ; for particles which touch the creature sink in 

 and are surrounded ; thus it obtains its food. 

 These slow flowing movements of the protoplasm 

 result in continual changes of shape; hence the 

 name, Amoeba, the mobile animal. Sometimes 



the island of pro- 

 toplasm, as it 

 changes its shape, 

 throws out, as it 

 were, capes and 

 headlands. These 

 projections, which 

 are presently 

 drawn in again, 

 are called pseudo- 

 podia or false feet. 

 They are charac- 

 teristic of the 

 whole group of 

 Amceba - like ani- 



FlG. 4. Section, highly magnified, of a mals, which are 

 two-layered animal, Hydra (Grade consequently 

 II.). EC, outer layer of Ectoderm; ,, , r>u' 

 En, inner layer of Endoderm ; /, Called Khizopoda, 

 lamella dividing the two, represented the TOOt - footed, 

 by a line; n, nuclei of the cells; v, Thp nrnHnrtinn r>f 

 thin vacuoles of small interstitial cells ; 



, the Enteron or digestive cavity. new individuals IS 

 accomplished by 



the division of the old cell into two. Thus it 

 may be said that there is always a bit of the old 

 cell remaining, though divided into fragments ; 

 and for this reason the Amceba-like Protozoans 

 have been fancifully called " immortal." 



GRADE II. The Two-layered, or Diploblastic 



