28 



LEON J. COLE 



He apparently made no test, however, of the proportion of 

 locomotion forward and backward in the absence of directive 

 stimuli. 



{d)lV 



WV 



Fig. 9 Diagram of a spatangoid. i — -v, Loven's designation of the ambulacral 

 areas; (a) — (e), corresponding arms of the starfish with respect to the position of 

 the madreporic plate, as designated by Jennings (cf. fig. 1); 1 — 5, interambulacral 

 areas, according to Loven. an., anus; mo., mouth; 7n.p., madreporic plate; 

 AA, line marking bilateral symmetry of form. This diagram should be com- 

 pared with fig. 5. 



VI. CONCLUDING DISCUSSION 



Granting that the observations which have been presented 

 establish satisfactorily the fact of "a 'physiological anterior' in 

 the starfish — that a particular part tends to precede most often 

 in locomotion — three possible explanations to account for this 

 phenomenon suggest themselves. First, there may be a defi- 

 nite morphological relation between the bilateral larva and the 

 adult which establishes what shall be 'anterior' in the latter; 

 second, it may depend upon a proportional relationship in the 

 length of the rays; and third, it may be related to the condition 

 of some other set of organs, such as the nervous system or the 

 water vascular system. 



