§3] 



GEOTAXIS 



119 



at any angle. As explained on p. 113, the intensity of gravity's 

 action will diminish as the sine of the angle of inclination of 

 the plate is diminished from 90° to 0°. We determined the 

 deviation of the slug 

 from a vertical position 

 upon plates at various 



inclinations, and after I 1 I I M I I I I I I I M I M Tl Uo" 



the lapse of a constant 

 time (45 seconds). The 

 experiments were per- 

 formed in a dark box. 

 The number of tests 

 made at each inclina- 

 tion was sixty. The 



time required to re- ; 25°| | J^-i^l^n I I I I I I i i I i I 170° 

 spond fully to gravity 

 did not vary appreci- 

 ably with the angle of 

 inclination. The re- 

 sults obtained indicated 

 that the deviation of 

 the slug from vertical- 

 ity diminished with the 

 cosine of the angle 

 made by the plate. 

 The relation between 

 the angular deviation 

 from verticality and 

 the sine of inclination 

 of the glass plate is 

 graphically represented 

 in Fig. 25. The con- 

 clusion from the ex- 

 periments is that the 

 lower limit of the sen- 

 sitiveness of Limax to''^ gravity is extremely small, below 

 0.13 g., and that as the angle of inclination of the plate 

 diminishes the deviation from 45° towards verticality dimin- 

 ishes in accordance with the relation : B = a- sin 6, in which 



90° 80° 70° 60° 50° 40° 30° 20° 10° 0° 



ANGLE OF INCLINATION OF SURFACE TO HORIZONTAL 



Fig. 25. — Curves showing relation 'between the 

 sine of the angle of inclination of a glass plate 

 and the angular position of a slug which was 

 first placed on it in a horizontal position and 

 then left for 40 seconds in the dark. Curve A 

 is constructed by drawing ordinates from the 

 heavy horizontal line, 0°-45°, corresponding to 

 each angle of inclination of the surface (laid 

 off as abscissae) . The lengths of the ordinates 

 are determined by the number of degrees of de- 

 viation of the axis of the slug from 45° towards 

 90°. 45° is taken as a base, since it would be 

 the mean angular deviation from the initial 

 position of a slug crawling undirected upon a 

 horizontal plate. Curve B is constructed by 

 drawing down from the base ordinates propor- 

 tional to the natural sines of the different an- 

 gles of inclination of the glass plate. 



