488 Jourj^al of Comparative Neurology and Psychology. 



low temperature. The reflex, though generally of shorter dura- 

 tion than when produced by heat, was, nevertheless, unmistakable. 

 The characteristic spinning motion, and the final rigid extension 

 of the wings could often be observed. These flies soon became 

 motionless, but they did not die. They could be revived by rais- 

 ing the temperature. 



Since extremes of both heat and cold produced, through the 

 nerves concerned with temperature, such marked motor reflexes, 

 I decided to try the effect of intense light acting through the optic 

 nerves. The positive phototropism of Drosophila to light of 

 various intensities has been described in a former paper (Carpen- 

 ter '05). In using the highest intensity at that time available, 

 an arc light of 250 candlepower, it was noted that after continued 

 exposure at a distance of 40 cm. an insect became extremely 

 active, flying and hopping about irregularly, and giving little or 

 no evidence of a directive control. It seemed probable that this 

 excessive activity might have led to a true convulsive reflex had 

 the intensity of the light been still further increased. For the 

 purpose of testing this Prof. C. W. Hottes, of the Botanical 

 Department of the University of Ilhnois, kindly placed at my 

 disposal an arc light of 480 candlepower, conveniently suspended 

 in a dark room. A small glass box was constructed, consisting of 

 two compartments separated by a vertical glass plate. In one of 

 these compartments the flies were placed; the other was filled 

 with water to serve as a heat screen. A thermometer was placed 

 just behind the heat screen in contact with the vertical glass plate 

 separating the two chambers. 



When flies contained in this apparatus were brought to a dis- 

 tance of from 2 to 3 cm. from the arc Hght their movements at 

 first, while rapid and irregular, were not true convulsive reflexes. 

 The front wall of their compartment had an initial temperature 

 of 25° C. ; after about a minute this temperature rose, in spite of 

 the heat screen, to 30° C. The flies then gave the convulsive 

 reflex, tumbhng and whirling about on the floor of the compart- 

 ment, and showing no signs of orientation. Up to this time there 

 had been no evidence of a reversal of their phototropism from 

 positive to negative. Removed from the influences of the light 

 and heat they resumed their ordinary activities. 



To determine whether or not the intense light was a factor in 

 inducing this convulsive reflex the flies were subjected to the same 



