COORDINATION AND RIGHTING IN THE STARFISH. 



365 



same time, but were not attached. Soon these latter straightened 

 out again and the attachment of c was loosened. Twenty 

 minutes later c and d bent over together and succeeded in obtain- 

 ing a hold between b and a (Fig. iB}. By their concerted effort 

 they succeeded in pulling the body over, e crossed over a (Fig. 

 iC), and at the end of 44 minutes from the time it was placed 

 on its back the starfish had completely righted itself, turning, 

 as seen, on arms a and b. It now remained quiet for two or 

 three minutes, and then began crawling with b in advance, the 

 movement being, however, very slow, as if there were not com- 

 plete coordination of all the arms. 



a 



FIG. i. Diagrams of righting movements of a starfish having the radial nerves 

 severed at the bases of all the arms. Arms attached to substratum are indicated 

 by X- Arrow shows direction of turning. 



Experiment 2. (Specimen No. 14.) -In eleven preliminary 

 trials this animal righted itself in from one to five minutes, the 

 average being 2.6 minutes. In ten of the trials it turned on arms 

 a + e. An incision was now made on the oral side at the base 

 of each arm, severing not only the radial nerve and water canal, 

 but also the muscles and other internal organs, and leaving 

 only the aboral arch of the external skeleton intact. It was now 

 placed on its back in the water. It is unnecessary to give in 

 detail the movements of the arms; it is sufficient to say that 

 they at once began active but entirely uncoordinated movements. 



