Holmes' Tropisms of Animals. 
13 
THE TROPISMS AND THEIR RELATION TO MORE 
COMPLEX MODES OF BEHAVIORf 
S. J. Holmes. 
The subject of animal behavior has been of interest to human 
beings from the earliest times, but it has not been taken very 
seriously until a comparatively recent date. The ways of animals 
were considered curious, interesting and in many ways useful 
things to know about, but the great theoretical import of animal 
psychology was unsuspected until it came to be recognized that 
our own minds are the outgrowth of the animal mind, and that 
to obtain a truly scientific human psychology it is necessary to 
have a clear insight into the psychology of the lower animal from 
which we are descended. Near the middle of the nineteenth 
century Herbert Spencer enunciated the principal that, “If the 
doctrine of evolution be true the inevitable implication is that 
mind can be understood only by observing how mind is evolved,” 
and he boldly plunged forward upon an undertaking to remodel 
the science of psychology from the genetic standpoint. The result 
was the publication in 1856, three years before the appearance 
of the Origin of Species, of the Principles of Psychology, a work 
which for sheer originality, independence of treatment and pro¬ 
found grasp of the subject stands almost without a rival in the 
history of science. 
Notwithstanding the work of Spencer, genetic psychology 
was given perhaps its greatest impetus by Darwin, not only 
through his influence in establishing the general doctrine of 
organic evolution, but also through his careful work on and illu¬ 
minating treatment of the mental life of animals. The admirable 
and original chapter on Instinct in the Origin of Species, the 
chapters on the comparison of the mental powers of man and the 
lower animals in the Descent of Man, and the work on Expression 
of the Emotions in Man and Animals were all substantial contri¬ 
butions to the science which were very influential in stimulating 
further work. 
It is not my intention to treat of studies of animal behavior 
undertaken from the standpoint of evolution, but to discuss 
another and in many respects complimentary aspect of the sub¬ 
ject, that of analysis, or the effort to discover the causal 
mechanism of animal activities by resolving them into their com- 
1) Adapted from a lecture before the Wisconsin Natural History Society, 
at Milwaukee, Oct. 26, ’ll. 
