334 ROBERT M. YERKES 



tium." The glass T rests upon a piece of plate glass two-thirds 

 of which is covered, as is indicated in the figure, by layers of 

 white blotting paper to the thickness of 5 millimeters The 

 remainder of the base-plate is left uncovered in order that a 

 piece of rubber, R, may be inserted under the T as insulation 

 for two copper electrodes, E. 



Wooden tubes which serve as artificial burrows appear at 

 En.T. and Ex.T. The former may be designated the entrance 

 tube and the latter the exit tube. The "tubes" are made by 

 boring a 13 millimeter hole the length of a block of soft wood 

 14 by 4 by 4 centimeters. The block is then split. The ends 

 of the hole are bevelled and sandpapered and the lower half 

 is lined with white blotting paper. 



A strip, 1 centimeter wide, of No. ^ sandpaper extends across 

 one arm of the T, as shown at P, (figure 1 ) ; and just beyond 

 the outer edge of the sandpaper, resting on the plate glass base, 

 is the piece of corrugated rubber, R, in two of the grooves of 

 which lie the copper electrodes, E. 



In the early experiments with worm No. 2, a piece of glass 

 carrying a strip of blotting paper which had been soaked in 

 strong salt solution, 3 took the place of the rubber and the 

 electrodes. 



This apparatus was designed to test the ability of earth- 

 worms to "learn" to follow a simple path and to avoid an in- 

 jurious chemical (or electrical) stimulus by reacting negatively 

 to a peculiar tactual stimulus which regularly preceded the 

 chemical. The experimenter had in mind two questions : First, 

 can the worm profit by experience; second, can it "associate" 

 the tactual stimulus with the chemical and acquire the habit 

 of regularly responding to the sandpaper as tho it anticipated 

 the effect of the salt. 



In September, 191 1, a number of manure worms were col- 

 lected at Cambridge, Massachusetts, for this investigation. 

 Those selected for use were kept in earthenware jars, 10 centi- 

 meters deep by 7.5 centimeters in diameter, in a moist mixture 

 of earth and horse manure. Number 2, the subject of this 

 report, was, from the first, an active, vigorous individual, which 

 reacted well in the apparatus and evidently throve on the treat- 



* The solution was made by dissolving 60 grams of c. p. sodium chloride in one 

 liter of distilled water. 



