Experimental nystagmus is induced by rotation of the animals in a clock-wise and counter clock-wise direction. It seems to be of longer duration in the pigeon than in the rabbit and rat. There are apparently many factors which influence the rotational response, such as weight, age, muscle tonus, position of the head, and previous environmental condition of the animal. The experiments indicate a reduction of the duration of nystagmus with repeated performance, which the author suggests as approximating the commonly called "learning curves." This indicates that the doctrine of the invariability of a reflex response is in need of revision.