RESPONSES TO LIGHT OF THE ROACH. 385 



ing does not affect the retentiveness of larval roaches. Several 

 of my larval roaches moulted during the progress of these 

 experiments; but, except when the experiment was performed 

 before the body had become sufficiently hard to permit freedom 

 of movement, I never once detected any interference with the 

 retentiveness of the roach. When the health of a roach is im- 

 paired and especially when it is dying, there is a marked falling 

 off in its ability to retain the results of experience. 



What is the meaning of this refusal of these roaches to enter 

 the dark chamber? Can it be that a few electric shocks have 

 produced such physiological changes in these insects that whereas 

 once they reflexly sought the darkness now they reflexly shun it? 

 Or, is it a case of having learned to avoid a particular dark place 

 on account of certain unpleasant experiences? To find an 

 answer to this question use was made of discrimination box 

 number three. As has been stated above, this was a glass box 

 25 centimeters long, 8 centimeters wide and 8 centimeters high, 

 in one end of which was a dark chamber 15 centimeters long. 

 The lighted portion of trie box communicated with the dark 

 chamber by means of a door 3 centimeters wide and 2 centimeters 

 high. Roaches that had thoroughly learned to avoid the dark 

 chamber were tested in box number two and then transferred, at 

 once, to the lighted portion of box number 3. Immediately 

 such a roach would enter the dark chamber. It was then replaced 

 in the lighted portion of box number 2, where it refused to enter 

 the dark chamber and could not be induced to do so by the 

 method mentioned above. Adult females, adult males, larval 

 females one half inch long and larval females one fourth of an 

 inch long were put through this test. With all such roaches that 

 had thoroughly learned to avoid the dark chamber of discrimina- 

 tion box number two the responses were as stated. Roaches 

 which had not thoroughly learned the refusal reaction and adult 

 females with amputated antenna?, on being returned to the 

 lighted portion of box number two, usually entered the dark 

 chamber. To my mind this test is a conclusive proof that the 

 change in the behavior of these insects is not due to a physio- 

 logical reversal of the phototropic responses of the roaches; but 

 a case of learning, by experience, to avoid a specific dark place 

 because of certain disagreeable experiences connected with it. 



