THE GENERAL, SCHEME 



"adult" size (Fig. 2). Sometimes the parent animal breaks 

 up by multiple fission into a relatively large number of very 

 small daughter cells resembling spores (Fig. 3). 



Reproduction by fission is so easy that in the course of 

 evolution the animal kingdom held on to it for a long time, 

 and many animals higher than the unicellular animals made 

 use of it. Some of the worms, for example, split in two trans- 

 versely by forming an extra head from some of the segments 

 near the middle of the body (Fig. 4). This head, with the 

 rest of the worm that lies behind it, drops off and wriggles 

 away, while the original worm forms a new tail at its trun- 

 cated posterior end. Sometimes the worm breaks up into a 

 whole chain of segments each of which becomes a new worm. 



Reproduction by budding also continued in higher ani- 







^Ti^^te^^^j^ 



'■' \ 



Fio. 2. A one-celled animal, AcanthocystiSy reproducing itself by 

 budding. 3 buds are seen. Greatly magnified. After Schaudinn. 



{ 5 } 



