STUDIES ON THE DYNAMICS OF MORPHOGENESIS 



IN EXPERIMENTAL REPRODUCTION 



AND INHERITANCE 



IX. THE CONTROL OF HEAD-FORM AND HEAD FREQUENCY IN 

 FLANARIA BY MEANS OF POTASSIUM CYANIDE 



C. M. CHILD 



Hull Zoological Laboratory, University of Chicago 



TEN FIGURES 



In the sixth paper of this series (Child 13 c) the existence 

 of a metabolic gradient along the chief axis of the planarian 

 body was demonstrated and in the seventh and eighth papers 

 (Child, '14 a, '14 b) the analysis of the metabohc factors con- 

 cerned in the reconstitution of heads on isolated pieces was begun. 

 In these papers it was shown, first, that pieces of different lengths 

 from different body regions showed different degrees of stimu- 

 lation and that the greater the degree of this stimulation the 

 lower the head-frequency, and second, that it is determined 

 within a few hours after section and during the period of stimu- 

 lation of the piece whether a head shall be formed or not. 



The relations between length of piece, region of body, degree 



of stimulation after section and head-frequency constitute 



one series of data in the analysis of the factors of head-formation. 



From these data the conclusion was drawn that head-freciuency 



rate x 



= '- where x represents the cells directly concerned in head 



rate y 



formation and y the other parts of the piece (Child, '14 b). 



Another series of data to be considered in this and following 

 papers consists in the experimental alteration and control of 

 head frequency. These data afford a means of testing the for- 

 mula stated above and throw further light on the problem in 

 other ways. 



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