FRANDSEN. — REACTIONS OF LIMAX MAXTMUS. 



219 



more or less positive response. In the case of animal No. 3, removal of 

 the eyes did not seem to altogether prevent, though it considerably 

 reduced, the negative response. Thereupon, the ventral tentacles were 

 also amputated and the result then was a slight positive response. Since 

 there is probahly some shock to the nervous system by the amputation, 

 these results ought to be corroborated by other experiments where the 

 eyes are covered over with some substance to shut off the rays of light. 

 This, I have not yet succeeded in doing satisfactorily. 



The experiment of removing only one of the ocular tentacles was tried 

 on two different animals with the following interesting results. 



TABLE XIV. 



Comparison of Effect of Amputation of Right and Left Dorsal 



Tentacles. 



In the case where the right tentacle was removed, the animal still 

 responded negatively with considerable precision. Amputation of the 

 left tentacle, in the case of No. 2, on the other hand, resulted in a slight 

 positive phototaxis. While these two cases by themselves have little, if 

 any, significance, taken in connection with facts now to be discussed, they 

 seem to indicate a greater degree of sensitiveness to strong light on the 

 part of the left side of the animal's body than the right. 



It will be remembered that our thigmotactic experiments pointed to a 

 possible asymmetry in the sensitiveness of the right and left tentacles of 

 the slug. Do we find a similar asymmetry in the responses to light? 

 Table XV. gives the responses of right and left sides respectively for the 

 18 series. Column 1 gives the number of the series, column 2 the in- 

 tensities of light, columns 3 and 4 the total angular migrations in a positive 

 and negative direction for the series when the right side was exposed to the 

 light, and the fifth column the algebraic average (positive or negative) 

 phototactic response of the right side. Similarly, the next three columns, 

 6, 7, and 8, give the responses of the left side. Column 9 represents 

 the total movement of the series in degrees to the right. This result was 

 obtained by adding the total positive responses of the right side (column 3) 



