STUDIES ON THE DYNAMICS OF MORPHOGENESIS 



AND INHERITANCE IN EXPERIMENTAL 



REPRODUCTION 



VII. THE STIMULATION OF PIECES BY SECTION IN PLANARIA 



DOROTOCEPHALA 



C. M. CHILD 



Frovi the Hull Zoological Laboratory, University of Chicago 



FOUR FIGURES 



I. METHODS 



By means of the direct susceptibility method it is possible to 

 follow the changes in rate of metabolism resulting from section 

 in pieces. This method, which has been described in detail else- 

 where (Child '13 a), consists in determining the susceptibility 

 of individuals or pieces to concentrations of KCN, alcohol, and 

 so forth, which kill within a few hours. In such concentrations 

 the higher the general rate of metabolism the greater the suscepti- 

 bility and the shorter the life of the animal or piece in the solution. 

 In this way the susceptibility serves as a means of distinguishing 

 and comparing the general rate of metabolism in different indi- 

 viduals, regions, or pieces. Since the changes in susceptibility 

 following section depend upon size of piece and region of the body 

 from which it is taken it has been found most satisfactory to 

 determine the susceptibility of series of pieces, representing both 

 different fractions of the body length and different regions of the 

 body, at various intervals after section. Of course a different 

 series of pieces must be used for each susceptibility determination 

 but by standardizing the material used and the external conditions 

 a remarkable uniformity of results is possible. 



The method of experiment is as follows: The bodies, exclusive 

 of the heads, of ten worms of equal length and similar physiologi- 



413 



