BILATERAL TENDENCIES IN PYCNOPODIA HELIENTHOIDES. 237 



RATE OF RIGHTING REACTIONS: Experiments carried out on April 4th, 1915. 



Temperature 10 C. 

 Number of Trials. Time. 



ist trial 60 sec 



2d " 60 " 



3d " 60 " 



4th " 30 



5th " . 50 " 



6th " 60 ' 



7th " 40 " 



8th ' 40 " 



9th 40 The first 20 trials are in the same direction, 



loth . 60 , e. g., toward the anterior end. The average speed 



nth 70 O f righting in these trials equals 66 sec. 



I2th " 70 " 



I3th ' 70 " 



I4th " 65 " 



I5th 70 



i6th " 65 " 



1 7th " 75 " 



i8th " 85 " 



1 9th no 



20th " 120 " 



2ist " 70 " Righting movements toward posterior end. 



22d " 50 



23d " 50 " 



24th " -55 



25th " 60 



26th " 60 " , Righting movements toward the anterior end. 



27th " 50 " | The average speed equals 55 sec. 



28th " 40 



29th ' 40 



30th " 60 " 



3ist 90 



32d " 70 " Righting movement toward posterior end. 



33d " 40 



34th " .30 



35th " 30 



36th " 40 



37th " 40 



38th " 44 



39th " 50 " I Righting movements toward the anterior end. 



40th " 55 The average speed equals 52.7 sec. 



4ist " 60 



42d 60 



43d " 65 



44th " 65 



45th " 70 



46th " 90 " 



