REGULATION AND FISSION IN PLANARIA. 



complexes of the whole, thus a piece from the anterior regions 

 of the body is functionally much more "anterior" than a piece 

 from the middle of the body; consequently in the new wholes 

 formed from these pieces we shall find relative differences in size 

 of various parts. In the "anterior" piece, for example, the 

 anterior region will be much larger than the posterior and in the 

 piece from the middle of the body the two will be about equal. 



3 



a 



w 



b 



4 



FIGS. 3-5. 



In normal animals the pharynx is situated in the middle of the 



body but in those new animals formed from the pieces the 



physiological or functional middle does not coincide with the 



