stimuli mechanically as directed by his instincts. Now, as is well known, the development of instinct in animals is a dreadfully slow process. There is no known case of the development of a single instinct in domestic animals in all the history of their domestication. Whatever instincts they possess they brought with them from the wild thousands of years ago. Therefore, all Rollo's actions were ganglionic discharges ;mechanically determined by the instincts that had been developed and fixed in the species thousands of years ago. Very well. It is clear, therefore, that in all his play with me he would act in old-fashioned ways, adjusting himself to the physical and psychical factors in his environment according to the rules of adjustment which had obtained in the wild and which had become part of his heredity.
Rollo and I did a great deal of rough romping. He chased me and I chased him. He nipped my legs, arms, and hands, often so hard that I yelled, while I rolled him and tumbled him and dragged him about, often so strenuously as to make him yelp. In the course of the play many variations arose. I would make believe to sit down and cry. All repentance
