FRANDSEN. 



REACTIONS OF LIMAX MAXTMUS. 



199 



Still more conclusive results were obtained by the substitution of wood 

 or vaselined glass surfaces for the clean glass plate. In order to make 

 sure that the animal's power to hold on varied with different surfaces, 

 and to determine approximately the relative strength of the adhesion, Dr. 

 Davenport suggested the use of a delicate spring balance, such as are used 

 in weighing letters. The animal was placed on a horizontal glass plate. 

 When it had oriented itself, and was moving forward, the pan of a letter 

 balance was held against the side of the animal and gradually increased 

 pressure exerted until the animal was made to sli]) along the plate. The 

 maximum reading (in ounces) on the indicator was noted. Then the same 

 animal was placed on a wooden plate and a similar test made under 

 like conditions of movement and activity. The same was done on the 

 vaselined plate. A number of such tests were made on each individual. 

 In order to avoid possible differences in results due to a gradual de- 

 terioration in the condition of the animal, the sequence of the surfaces 

 was varied in the successive sets (three) of trials so that each surface was 

 once employed for the first experiment of a set. This method proved 

 fairly satisfactory and gave in some instances very striking results. 



TABLE VI. 



Amount of PniiSSURE required to dislodge the Slug from Different 



Horizontal Surfaces. 



The results recorded for each individual are the averages of three 

 trials on each of the surfaces used. The table shows a considerable differ- 

 ence in the degree of adhesion to the different surfaces. In the last four 

 cases the animals were all very large. They were in excellent condition, 

 having just been captured, and secreted a sticky slime in large quantities. 



