author's abstbact of this paper issued 

 by the bibliographic service, march 8 



STUDIES ON THE DYNAMICS OF MORPHOGENESIS 

 AND INHERITANCE IN EXPERIMENTAL 

 REPRODUCTION 



X. HEAD-FREQUENCY IN PLAN ARIA DOROTOCEPHALA IN RELATION 

 TO AGE NUTRITION AND MOTOR ACTIVITY 



C. M. CHILD 

 Hull Zoological Laboratory, University of Chicago 



THREE FIGURES 



Analytic investigation of reconstitution or regeneration in iso- 

 lated pieces of Planaria dorotocephala has shown that the process 

 is by no means uniform in different pieces, even in those from the 

 same animal. The structures produced at the anterior ends of 

 pieces present the most interesting conditions as regards varia- 

 tion, for they constitute a graded series ranging from normal 

 heads at one extreme, through various degrees of incomplete head 

 development, to a completely headless condition in which the 

 wound at the anterior end merely heals and nothing further 

 occurs. In spite of the fact that they actually constitute a graded 

 series, it has been found convenient for purposes of analysis to 

 divide the different types of anterior end into several groups rep- 

 resenting different degrees of departure from the normal and 

 approach toward the headless condition. These different groups 

 have been named, defined, and figured in earher papers (Child, 

 '11 a, '15 b, p. 106, '16). Investigation has shown further that 

 the character of the anterior end developing in an isolated piece 

 varies in a definite way with the length of the piece or the frac- 

 tion of body length represented by it and with region of body 

 from which it is taken (Child, '11 b, d). Moreover, it has been 

 found possible to control and alter experimentally to a very high 

 degree the character of anterior end produced. The results of 

 experiments with KNC (Child, '16) and temperature (Behre, '18) 



403 



