190"] Jennings. — Behavior of tJic Starfish. 123 



as a whole. "Whether he would explicitly postulate such an entity 

 for the particular case of the starfish I will not endeavor to 

 assert, but this would seem to be the logical result from his gen- 

 eral discussion. 



It is clear that such behavior presents problems of great in- 

 terest, and for their discussion we need above all things a thor- 

 ough knowledge of the facts. Preyer's account has been ques- 

 tioned ; how far is it correct, especially in the matter of the 

 variability of the reaction ? Does an extended study of the facts 

 justify the deep significance that Driesch has given to this be- 

 havior ? And how far does his general theory assist us in under- 

 standing it ? 



These and other questions will be kept under consideration 

 in the following account. Our method shall be to give an em- 

 pirical analysis, (1) of the various factors which determine the 

 behavior; (2) of the various factors which compose the liehavior. 

 followed by (3) a discussion of the results. The account is 

 based on a very large number of experiments and observations. 

 I have in my notes written records of the way the reaction oc- 

 curred in 1220 cases, and a very large number of observations 

 Avere unrecorded. It is hoped therefore to make the analysis 

 fairly adequate. 



Before beginning our account, it will be well to give outlines 

 of the starfish, with the designation of the five rays that we shall 

 employ throughout our account, as well as to define certain 

 expressions that we shall use. The starfish is given a bisymmet- 

 rical form by the madreporic plate, and the rays may l)e defined 

 with reference to this plate. Placing the starfish with dorsal 

 surface above and with the madreporic plate on that side of the 

 disk which is next to the observer, the ray to the left of the plate 

 will be called a, the next h, and so on to e, at the right of the 

 madi'eporic plate. Figs. 10 and 11 give these designations in 

 dorsal and ventral view ; they will be found useful in following 

 our descriptions of the reaction. 



For brevity we shall often say that the starfish uses certain 

 rays, as a and 6, for turning itself; this will mean that it takes 

 hold with these rays and turns on them, — the other rays .swing- 

 ing over. To say tliat the starfish "turns on," or "turns to- 



