Influence of Temperature on Rate of Regeneration in the Time-graded Regeneration Field in Planarians

INTRODUCTION THERE exists in planarians a time-graded regeneration field for head regeneration (Brandsted, 1946, 1956; A. & H. V. Brondsted, 1952). The characteristics of this field, expressed by rate of regeneration, are species-specific. The existence of this field ensures harmonious regeneration from cuts everywhere in the body, as a cut will always expose a 'high point' where regeneration of a head starts with greatest speed, thus taking the lead in organization and at the same time inhibiting head-forming tendencies elsewhere in the blastema (Brondsted, 1956). The factors underlying these characteristics of the field are unknown; the problems involved are being attacked from several angles in our laboratory. For the sake of this work it is of some interest to know how the different rates of regeneration at various levels in the time-graded fields might be influenced by various temperature levels.