558 Wisconsin Academy of Sciences, Arts, and Letters. 
The accuracy of response to red light was tested in one ex¬ 
periment. The culture was placed 20 centimeters from an 
opening one centimeter in diameter. A red glass was placed 
inside the box against the opening. The target shown in 
Figure 1 was used to count the sporanges. The number of 
sporanges on the glass after twenty-four hours was SO. 1.2% 
of these were on area 1, corresponding to the opening; 13.7% 
were on area 2; 28.7% on area 3, 18.7% on area 4, and 37.5% 
on area 5. The reactions toward red light are evidently very 
vague and uncertain. 
The results which have now been described indicate that 
Pilobolus aims point blank at a source of light, making no al¬ 
lowance for the distance through which the sporanges must 
travel; that is, it does not aim higher for a distant source of 
light than for a near one. To test this point still further, 
the -culture was placed in the same box with its center on a 
level with the middle of a four-centimeter opening. As in a 
previous experiment, it was placed on successive days at dif¬ 
ferent distances along the median line of the box. The glass 
upon which the sporanges were received was, however, always 
placed at a distance of 25 centimeters from the culture; thus 
if the sporangiophores aim higher as the distance from the 
source of light increases, the sporanges should strike the glass 
above the target when the culture is sufficiently far from the 
source of light. 
The target used in counting the sporanges is shown in Figure 
10. In this case the field was divided off into horizontal strips 
one centimeter wide, and they were numbered upward and 
downward from a line running through the center of the open¬ 
ing, the strip above being marked + and that below—. An 
area 14 centimeters wide was found to include nearly all the 
sporanges; those beyond this area were counted under the head 
“7+” 
The culture was placed successively at 25, 35, 40, 50, 65, 80, 
90, 100 and 110 centimeters from the opening, being left 
twenty-four hours in each position. With the culture at 25 
centimeters from the opening, the center of distribution of the 
