REACTIONS OF WHIP-TAIL SCORPION TO LIGHT 



255 



APPARATUS 



The apparatus used in these experiments needs Httle explana- 

 tion other than the diagram of figure 2. At one end of a table 3 

 meters long, a circle 50 cm. in diameter was marked out and 

 graduated in degrees. One axis {pp') was drawn through the 



Fig. 2 Plan of apparatus. About as a center a circle 50 cms. in diameter 

 was described and graduated in degrees. This is termed the 'observation circle.' 

 The axis pp' of the circle is parallel to the edge of the table and the axis yy' is 

 perpendicular to pp'. On the axis yy' two 15 watt Mazda lamps, A and B, were 

 set up, each distant 35 cms. from the center of the circle. On the axis pp' a 

 similar. lamp was mounted on a movable frame, C. Affixed at right angles to the 

 base of the frame, C, was a scale, V, reading as a vernier against the scale, S. 

 on the edge of the table. Light proof cases, s, s, s, enclosed each light except for 

 diaphragms 3 cm. by 3 cm. so placed that the beams of light transmitted each 

 centered at 0. 



center of the circle parallel to the edge of the table, and another 

 axis {yy') at right angles to the first. Fixed lights were located 

 at either end of the axis yy', equidistant (35 cm.) from the 

 center of the circle. A movable fight was arranged to slide 

 along the axis pp'. The frame on which this movable light was 

 carried had a scale comparable to a vernier which could be 

 read against a scale on the edge of the table. Each of the three 



