400 'Journal of Comparative Neurology and Psychology. 



home, a new incline was attached to the side of the stage which 

 was opposite the one to which the old incline was attached. If 

 after a lapse of five minutes no ants went down this second incline, 

 conditions were considered right for the test. The light was now 

 transferred to the opposite side of the stage. In each case the 

 halting movements of the ants showed that they were disturbed 

 (Fig. 6). In most cases, some of the ants w^ould finally go down 

 the new incline and in a few cases, after the lapse of several min- 

 utes, all of them would go down the new incline. These experi- 

 ments were tried on all of the ants used in the experiments on 

 heliotropism (p. 371). 



Similar experiments were conducted with marked individuals 

 of the species, Formica fusca var. subsericea Say, Myrmica 

 punctiventris Rog. The results harmonized with those derived 

 from experiments conducted with ants working in concert (Fig. 

 14, B\ Fig. 17, B, H, M); only, in almost every case, after a greater 

 or less lapse of time, the ant would usually find its way down the 

 old incline to the nest; and after a still greater lapse of time find its 

 way back to the stage. 



Fig. 16 illustrates how ants are disturbed by altering the 

 position of the light better than a multitude of words. From the 

 beginning to B the ants had been working by daylight, the light 

 coming from two windows, one on the south and one on the west. 

 From B to C the ants were working at night, the illumination 

 being furnished by electric lights and coming from the northeast. 

 From C to the end, the conditions w^ere the same as from J to B. 



To determine whether this effect was due to the intensity of the 

 light, to the direction of the rays or to heat, the following series of 

 experiments were conducted with Formica fusca var. subsericea 

 Say. 



That the effect described above was not due to heat, was proved 

 in the following manner. A cardboard stage was arranged with 

 its left side connected to the table by a cardboard incline. At the 

 right and left of this stage was placed a heat-filter, consisting of a 

 tall museum jar 34 cm. x 16 cm. x 7 cm., filled with cold distilled 

 water. At the beginning of the experiment, a 32 c.p. incandes- 

 cent lamp was placed behind one of these filters (usually behind 

 the one near the incline). After the ants had traveled the path 

 long enough to make the trips regularly and rapidly, the lamp was 

 transferred to a point behind the opposite filter. In every case 



