60 ELEMENTARY ZOOLOGY 



processes, the pseudopodia, and its body becomes con- 

 stricted. This constriction or fissure increases inwards 

 so that the body is soon divided fairly in two. There are 

 now two Amceba, each half the size of the original one; 

 each, indeed, actually one-half of the original one. The 

 original Amoeba was the parent; the two halves of it are 

 the young. Each of the young possesses all of the char- 

 acteristics and powers of the parent ; each can move, eat, 

 feel, "grow, and reproduce by fission. The only change 

 necessary for the young or new Avt&b'a to become like its 

 parent, is that of simple growth to a size about twice its 

 present size. The development here is reduced to a 

 minimum. Just as the simplest animals perform the other 

 life-processes, such as taking and digesting food, breath- 

 ing and feeling, in an extremely primitive simple way, so 

 do they perform the necessary life-process of reproduction 

 or multiplication in the simplest way shown among 

 animals. 



In the case of Paramcecium the process of multiplication 

 is slightly more complex than that of Amoeba in the fact 

 that sometimes before the simple fission of the body takes 

 place the interesting phenomenon of conjugation occurs. 

 Paramoecium may reproduce itself for many generations 

 by simple fission, but a generation finally appears in which 

 conjugation takes place. Two individuals come together 

 and each exchanges with the other a part of its nucleus. 

 Then the two individuals separate and each divides into 

 two. The result of the conjugation, or the coming 

 together, of two individuals with mutual interchange of 

 nuclear substance is to give to the new Paramoecia pro- 

 duced by the conjugating individuals a body which 

 contains part of the body-substance of two distinct indi- 

 viduals. If the two conjugating individuals differ at all 

 and they always do differ, because no two individual 

 animals, although belonging to the same species, are 



