AMCEBA AND PARAMCECIUM 



35 



a fixed shape to the body, are all specializations which 

 make Paramcecium more complex than Amoeba. But the 

 whole body is still composed of a single cell, and there 

 is, as in Amoeba, no differentiation of the body-substance 

 into different tissues, and no arrangement of body-parts 

 as systems of organs. 



Paramcecium may occasionally be found reproducing. 

 This process takes place very 

 much as in Amoeba. The animal 

 remains dormant for a while, the 

 micronucleus then divides, the 

 macronucleus elongates and 

 finally divides in two, the proto- 

 plasm of the body becomes con- 

 stricted into two parts, each part 

 massing itself about thewithdrawn 

 halves of the macro- and micro- 

 nuclei, and lastly the whole breaks 

 into two smaller organisms which 

 grow to be like the original. 

 After multiplication or reproduc- 

 tion has gone on in this way for 

 numerous generations (about one 

 hundred), a fusion of two Para- 

 mcecia seems necessary before 

 further divisions take place. This 

 process of fusion, called conjuga- 

 tion, may be noted at some sea- 

 sons, 

 their buccal grooves together, 



~, .... FIG. 6. Parama'chim sp. ; 



1 wo Paramcrcia unite with buccal groove a t right. (From 



life.) 



part of the macronucleus and micronucleus of each passes 

 over to the other, and the irjxed elements fuse together 

 to form a new macro- and micronucleus in each half. 

 The conjugating Paramcccia now separate, and each 

 divides to form two new individuals. 



