STUDIES ON REGULATION. IV. 



SOME EXPERIMENTAL MODIFICATIONS OF 



FORM - REGULATION IN LEPTOPLANA. 



BY 



C. M. CHILD. 

 With 53 Figures. 



INTRODUCTION. 



The following observations and experiments on Leptoplana 

 constitute a part of a series of investigations of form-regulation 

 undertaken at the Zoological Station at Naples in 1902-3 during 

 occupation of a table granted by the Smithsonian Institution. A 

 part of the work on Cerianthus has already appeared (Child '03a, 

 '03b, '04a.) 



The work was undertaken primarily for the purpose of examin- 

 ing the relations between form-regulation and the mechanical 

 tensions resulting from the creeping and other movements in some 

 of the polyclad turbellaria. For this purpose is was desirable 

 that the direction of movement should be relatively definite in at 

 least some one of the forms studied. Many of the polyclads 

 show little definiteness of direction in their movements under 

 ordinary conditions. This is notably the case in the species of 

 Stylochus in which, as might be expected, corresponding form- 

 changes are almost completely absent. Leptoplana proved to be 

 the only form readily obtainable in large numbers at Naples 

 which fulfilled these conditions. The creeping movements of this 

 form are relatively definite in direction. 



If form in the Turbellaria is in any way dependent upon the 

 mechanical strains to which the tissues are subjected, it is to 

 be expected that in forms with tough, resistant tissues, the changes 

 in shape resulting from changes in mechanical conditions will 



