STUDIES ON REGULATION. 



V. THE RELATION BETWEEN THE CENTRAL NERVOUS 



SYSTEM AND REGENERATION IN LEPTOPLANA: 



POSTERIOR REGENERATION. 



BY 



C. M. CHILD. 

 With 47 Text Figures. 



A. INTRODUCTION. 



It is beyond the purpose of the present paper to review the whole 

 question of the relation between the nervous system and morpho- 

 genesis or the sustaining effect of "trophic" stimuli upon form. 

 It is hoped, however, that the observations and experiments to be 

 described, together with the interpretation offered, may serve 

 to throw some light upon this most interesting, but difficult 

 problem. 



The question of the relation of the central nervous system to 

 regeneration in the lower animals has been touched upon by vari- 

 ous authors. As regards Planaria, a species which has been the 

 object of study by many investigators, opinions differ to some 

 extent at the present time. It is well known that in this form 

 removal of the cephalic ganglia does not interfere with complete 

 regeneration, the ganglia themselves being regenerated from por- 

 tions of the nervous system which may be present. As regards 

 other parts of the central nervous system, however, Bardeen ('03) 

 holds to the opinion that some portion of the nerve cords or of one 

 of them must be present in order that regeneration may occur, 

 while Morgan ('98, '00, '01, p. 44,) believes that regeneration may 

 occur in pieces from the lateral region of the body which contain 

 no part of the longitudinal cords. In an interesting paper dealing 



