16 LEON J. COLE 



in the axes of bilaterality, it seems very doubtful whether the 

 tendency to bilaterality in this respect can have significance in 

 accounting for the noticeable bilaterality with respect to loco- 

 motion, in spite of the fact that the evidence seems to show that 

 on the whole there is a slight tendency for arms e and a to be 

 longer than the others. One is inclined to believe rather that 

 both these results may be a more or less complete expression of 

 factors or tendencies of development or organization. 



3. Persistence of the irnpulse 



Reference has already been made (p. 5) to the 'impulse' of 

 a starfish to move in a certain direction, once it has estab- 

 lished movement in that direction — a sort of momentum of 

 physiological reaction which causes a certain behavior to persist 

 for a time even against an adverse stimulus (Jennings '07, p. 

 115). This fact has more recently been confirmed by Cowles 

 ('11, p. 103), who remarks: 



A characteristic of the starfish is that when once the impulse to 

 move in a certain direction is formed, the starfish is quite persistent 

 in its behavior and continues to move in that direction; so when the 

 creature reaches the wall it ascends owing to the persistence of the 

 impulse .... 



This inherent stubbornness of Asterias forbesi may be seen 

 in table 3, which displays in detail the results of the whole series 

 of trials made in the present experiments, in the order of their 

 sequence. Here it is evident that the precaution taken to break 

 up the locomotive impulse (cf. p. 5) was inefficient, for although 

 there is some variation in the part advanced in successive trials, 

 in general the same one remains the temporary 'anterior' for 

 a considerable number of trials. Specimen No. 4 may be taken 

 as an example. In this case the subject first crawled with the 

 interradial area ea as 'anterior,' then followed seven trials with 

 e in advance, next one with de, one with d, another with de, 

 three with e, again de, three more e, and so on. The degree of 

 this persistence is shown by the records better than it can be 

 described. 



