Holmes' Tropisms of Animals. 
23 
animal reacts in a definite way to objects impressed on its retina 
we commonly say that it sees. These reactions to objects come to 
be very complex and specialized. They come to depend upon 
the size, form and color of the moving object. But it is not 
improbable that they have their primary roots in the positive and 
negative phototaxis of simpler organisms. Josiah Royce in his 
Outlines of Psychology has gone much farther than I should 
venture to do, in that he sees in the tropisms a set of tendencies 
which form a sort of fundamental background even in our own 
psychology. Objects of our own attention exercise a compelling 
force over us making us turn toward them. We involuntarily 
turn toward a person or thing about which we are curious; in 
fact it requires some voluntary effort not to do so. Is this con¬ 
tinual orientation to objects akin to orientation to light or an odor 
in the lower animals? According to Royce these reactions are 
fundamentally the same. Perhaps if we should follow the history 
of behavior closely enough in passing from lower to higher forms 
we should be able to fill in the intermediate steps. At present the 
connection is merely a suggestive hypothesis. 
Most of the work on tropisms that has been done thus far has 
consisted in determining the precise way in which tropisms are 
brought about, and the conditions by which they are modified. To 
find as it were what becomes of the tropisms in the course of 
mental evolution, how they are converted into higher forms of 
behavior, is a more difficult task. Voltaire has made the remark 
that we are governed by instinct as well as cats and goats. It is 
possible that we may be justified in going somewhat farther than 
the celebrated skeptic, in saying that to a certain extent we are 
governed by tropisms as well as insects and worms. 
Zoological Laboratory, University of Wisconsin. 
Madison, Wis., November 7, 1911. 
