1914] JOLIVETTE—PILOBOLUS 117 
of “heterogene induction.” According to Nott, the reaction of 
an organism to one of two stimuli excludes the effect of the second 
stimulus. His work was concerned with two very different kinds of 
stimuli, light and gravity. The reaction to the stimulus of light 
excluded any response to the stimulus of gravity. Recent workers, 
GUTTENBERG (2) and Ricuter (5), have interested themselves 
along the same lines. GuTTENBERG maintains that if the light 
stimulus be diminished’ sufficiently, a resultant reaction between 
light and gravity will occur; that Nott and the earlier workers 
had used light that was too intense. To RicHTER’s (5) criticism 
that his results were due to impure air, GUTTENBERG (3) responded 
by further work under improved conditions and reached essentially 
the same results as before. 
In experiments on simultaneous stimulation of Pilobolus by 
lights of the same kind or of different kinds, we are dealing, unlike 
either of the foregoing cases, with simultaneous stimuli of one 
Kind, namely, light alone. It was possible to have the stimuli at 
least approximately equal, and it was possible to have the arrange- 
ment such that neither source of stimulation had any advantage 
over the other. Further, the organism worked with was a simple 
one, the reaction concerning only a single cell. And the net result 
of the reaction was shown so plainly in the distribution of the dis- 
charged sporangia that it seems impossible that any indefinite- 
ness or uncertainty could be entertained as to the reaction. The 
sporangia clustered always about one or the other of the two 
Sources of illumination. There was no sign of a resultant reaction. 
Even if the individual sporangiophore did not receive equal illumina- 
tion from the two openings, if there were any resultant reaction, it 
would be expected that the sporangium would be found in a position 
between the two lights, depending on the ratio of their intensities, 
differences of composition, and the like. Thus, it would be expected 
- that all of the sporangiophores would be located between the two 
sources of illumination. Such a condition did not obtain in any 
case where the two light stimuli were used, whether or not they 
were the same as far as distribution in the spectrum was concerned. 
The Sporangiophore reacted to one or the other of the two stimuli. 
The results obtained at least suggest that one stimulus does not 
