Excerpt from chapter III: Subject of animal behavior has been of in- terest 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 animals from which we are descended. Near the middle of the nineteenth century Herbert Spencer enunciated the principle 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 1855, four years before the appearance of the Origin of Species, of the Principles of Psychology, a work which for sheer originality, independence of treatment and profound grasp of the subject stands almost without a rival in the history of the 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 illuminating treatment of the mental life of animals.