COORDINATION AND RIGHTING IN THE STARFISH. 367 



RIGHTING OF SPECIMENS WITH ONE OR MORE ARMS REMOVED. 



The removal of one or more arms gives opportunity to test 

 and observe the correlation in the remaining arms more closely. 

 This study was not carried far, and a single example will suffice. 



Experiment j. A starfish was tested a number of times and it 

 was found that it turned regularly on arms e -f- a. Arms b and 

 d were now severed completely at the base. If the animal now 

 continued to turn on e and a, the only other arm concerned would 

 be c, and it was expected that this would each time release as 

 soon as coordination was estab- 

 lished, allowing e and a to pull it 

 over. It was proposed then to 

 sever the nerve of c in order to 

 destroy its coordination with the 

 other arms, and to see if they com- 

 bined would still be able to pull it 

 over, or whether coordination might 

 be reestablished through the me- 

 chanical pull, without nervous con- 

 nection. In the first tWO trials FlG - 2 - Diagram of righting of 

 f . a starfish with arms b and d re- 

 after the operation the specimen , T 



moved. Nerves of other arms m- 



turned on e and a as expected (Fig. tact. 



2), but in the third trial c failed to 



coordinate properjy and finally it with a pulled over e, which 



was doubled under until these arms had crawled far enough to 



enable it to straighten out. 



This experiment is not mentioned so much for the result ob- 

 tained as to illustrate a possible method of studying coordination, 

 impulses, and the relative use of the different arms in the starfish. 

 It is important that the behavior of each specimen should be 

 studied carefully in the normal condition before the operation 

 is made. 



BEHAVIOR OF COMPLETELY SEVERED ARMS. 



Romanes ('85, p. 294) found that "single rays detached from 

 the organism crawl as fast and in as determinate a direction as do 

 the entire animals," and that "when inverted, separated rays 

 right themselves as quickly as do the unmutilated organisms." 



