728 Journal of Cojnparative Neurology and Psychology. 



The tropism theory, at least in its naive form, cannot be made to 

 ai^ply to the behavior of this larva. It has been already shown that, 

 although the general body-surface is sensitive to light, no orientation 

 is produced thereby. Again, if two of the three legs be removed 

 from one side of the body and the animal placed in the light, the 

 normal orientation takes place. The same results are obtained if the 

 ocelli on one side of the body are covered. Obviously, then, compen- 

 sation occurs so that even in the absence of the two legs the function 

 is taken up by the remaining one. 



Harper ('05) determined for the earthworm, Perichceta, that the 

 stronger the light, the more regular the reactions and the fewer the 

 random movements. The meal-worm exhibits the same condition. 



Geotactic responses. The larvae are positively geotropic. An indi- 

 vidual was placed on an incline in a dark-room where the only illu- 

 mination w^as from a red photograpliic lantern. Previously, it was 

 determined that the larva did not react to this light. The larva re- 

 acted to inclinations of 5 degrees or more, by moving down the 

 incline. Compared with phototactic responses, geotactic are insig- 

 nificant. If an individual be placed on an incline with light of 

 even low intensity falling from the lower end, the animal will move 

 up the incline rather than approach the light. 



In this connection, the reactions of those larvse which were found 

 running on the surface of the meal, were examined. It was sus- 

 pected that such larvse were either positively phototactic or negatively 

 geotactic. They proved to be neither. Intensity of light seems to 

 have some effect, for if a strong light be suddenly thrown upon them, 

 they immediately begin to burrow. A mechanical shock produces the 

 same effect. Thigmotactic reactions were tried, such as sifting meal 

 upon them or piling it in front of them as an invitation to burrow, 

 but none did so. 



It is evident that this larva, low in the scale as it is, presents highly 

 complex behavior, the factors of which" are but slightly known. 



New York. October 15, 1909. 



