238 H. P. KJERSKOG AGERSBORG. 



47th 80 [ Righting movement toward the posterior end. 



1 Abnormal turn toward right angle of anterio- 



48th 180 



) posteno ends. 



49th " 50 " Righting movements toward anterior end. 



50th 60 The average speed equals 55 sec. 



The total average speed of the normal turns equals 57.1 sec. 



trials. At this point the writer thought that the star was learning 

 to do the righting more quickly than at first, but the subsequent 

 trials disprove it. After this last trial, three of equal speed follow, 

 each taking only 40 sec., but after these there is a slowing up in 

 speed, an indication of fatigue. The speed is now gradually 

 diminished until at the twentieth trial, when it takes two minutes 

 in righting itself. Following this is a righting toward the opposite 

 side, at a speed of 70 sec., but the succeeding ten trials are all 

 again in the same direction as at first, and with an average 

 speed of 55 sec., per righting. Then follows another turn 

 toward the posterior end, with a speed of 70 sec. This 

 is followed by fourteen turns toward the anterior end with 

 an average speed of 52.7 sec. Now follows the abnormal 

 turn described above, a turn toward the right side, with a 

 speed of three minutes, followed by two turns toward the 

 anterior end with an average speed of 55 sec. per righting. 

 Here ends the experimenting on right movements on this par- 

 ticular individual. The total average speed per normal rightings 

 is 57.1 sec. per righting. The series of rightings in one direction 

 indicate fatigue toward the last, or a decrease in speed of righting; 

 a turn toward the posterior end is followed by an increased speed 

 in the succeeding rightings toward the anterior end, which, 

 however, soon decreases. Whatever this may indicate, one 

 thing is apparent: that Pycnopodia is able to right itself in more 

 than one way, but that it turns more easily and far more fre- 

 quently toward the anterior than toward the posterior end; 

 that it never turns twice in succession toward the posterior end. 

 These trials on righting reactions were made on a small indi- 

 vidual of four inches in diameter, and which had 13 rays. This 

 specimen was kept in a cage of six by four by one feet in size. 

 The cage consisted of a wire-aquarium which was anchored to a 



