BRADLEY M. PATTEN 439 



the eyes were both found to be satisfactory and one or the other was 

 used, without preference, in the series of experiments. 



1. Asphaltum varnish was apphed with a camel's hair pencil to 

 the surface of the eye and allowed to dry until sticky. A cap of tin- 

 foil cut to fit over the eye was then set in the varnish and allowed to 

 dry in hard. Finally another coat of asphaltum was put over the 

 cap, especial care being used to seal the edges tightly. 



2. Rubber adhesive tape was given two coats of asphaltum varnish 

 on the fabric surface. When the second coat had dried, the tape was 

 cut into caps of the desired size, which were pressed firmly over the 

 eyes. The caps were then sealed on with asphaltum varnish and 

 allowed to dry. 



Subsequent microscopical examination of cleaned exoskeletons of 

 animals in which the eyes had been capped in these ways gave no 

 indication of light leakage. Furthermore, either type of covering 

 could be removed, leaving the eye uninjured for control experiments. 



The first animals handled after the capping of both median eyes 

 and both lateral eye groups showed still a well defined sensitiveness to 

 light. After careful rechecking of the work for possible light leakage 

 around the caps showed that the eyes were effectively covered, a 

 systematic search was begun for cutaneous photosensitive areas. ^ 

 Animals were placed under vertical illumination of just sufficient in- 

 tensity to make their outlines discernible and searched with a point of 

 intense light obtained by placing a tungsten flashlight bulb in place 

 of the ocular of a compound microscope and converging the rays through 

 the objective (3). As might be expected, the areas of the body cov- 

 ered by thick, heavily pigmented chitin were insensitive to light. 

 This narrowed the search to two locahties: the "feeling legs" (see 

 Fig. 2) which had already been demonstrated to be sensitive to touch 



^ The possibility that blinded scorpions might be reacting to the heat of the 

 light was tested in the following way. Animals were illuminated from one side by 

 hght of 120 candle meters. On the opposite side, 20 cm. distant from the scor- 

 pion, was placed a flatiron emanating heat rays plainly discernible to the back of 

 the hand. The light drove both normal animals and animals with their median 

 and lateral eyes capped toward the iron until they burned their feelers on it. 

 In spite of their crudeness these experiments served to rule out the possibility of 

 a heat reaction playing any part under the conditions of these experiments. 



