5/0 Wisconsin Academy of Sciences, Arts, and Letters. 
The Response of Pilobolus to the Stimuli of two Suc¬ 
cessive White Lights of Equal Intensity. 
The object of our next series of experiments was to deter¬ 
mine to what extent the sporangiophores can change their aim 
during the morning, and whether the discharge of the spo¬ 
ranges can take place while a heliotropic reaction is in progress. 
The sporangiophores in a culture are not all at the same 
stage of development at the same time. This is well seen 
in the evening when the tip of the sporangiophore is swelling 
to form the sporange. Upon some sporangiophores, the only 
indication of a sporange at this time is a, small yellow- knob, 
while on others immediately adjacent the sporanges are full- 
sized and turning dark. The latter are something more than 
an hour ahead of the former. In consequence of these differ¬ 
ences, the sporanges do not mature at the same time and are 
not discharged at the same time. It requires at least an hour 
for the discharge of the entire crop. Alt any particular mo¬ 
ment during the time of discharge, some are on the point of 
discharging, others will discharge in a few minutes, and still 
others may not discharge for an hour. 
The cardboard box used in the preliminary experiments 
upon simultaneous stimulation was used for these experiments. 
The two holes in the end of the box were 1.25 centimeters in 
diameter, 7.5 centimeters apart, and 5.5 centimeters from the 
bottom,. In order that the results might be as clean-cut as 
possible, the distance from the culture to the'openings was 
made comparatively small—15 centimeters. The culture was 
laid on its side on the bottom of the box, with the surface of 
the culture facing the openings and equidistant from them. 
The culture was propped securely at the sides to prevent- its 
rolling over should the box happen to be jarred. As before, 
the sporanges were caught on a glass plate placed inside 
against the end of the box. The form of chart from which 
the records were made is given in Figure 15. A vertical 
line down the center of the field divides it into right and left 
halves and each half is subdivided by a vertical line through 
