Harvard Psychological Studies, Volume 2

by Unknown

TABLE IX. GEOTAXIS IN FRONT OF WINDOW

	10				12				14				16				18				Totals
	+	–	±		+	–	±		+	–	±		+	–	±		+	–	±		+	–	±
5°	14	5	1		11	7	2		11	9			13	7			8	10	2		57	38	5
10°	13	7			12	7	1		13	6	1		16	4			14	6			68	30	2
15°	17	3			14	6			16	3	1		17	3			9	11			73	26	1
20°	12	8			17	3			18	1	1		19	1			14	6			80	19	1
25°	18	2			19	1			19	1			17	3			16	4			89	11

From this table it appears that the crayfish is positively geotactic, and that the positive geotaxis increases regularly with the increase in inclination. As a check on these results another set of experiments was undertaken with different animals under different conditions. The board was placed on a level table in the centre of a darkened room, and the operator stood behind a screen so as to be quite hidden from the animals. In order to observe the orientation a 2 c. incandescent electric light was suspended directly above the spot where the animals were set, at a distance of 60 cm. above the board. Each animal of a group of five was set five times in each of four positions, viz., head down the incline, head up the incline, and at right angles to it with first the right and then the left side down the slope. The results were as follows: