84 'Journal of Coinpnrnfive Neurology aud Psychology. 



ton suggests/ it must be found in the earliest reflexes of the embryo 

 as observed in these experiments, and if it is possible to trace the 

 development of a "simple reflex" into a form of acknowledged in- 

 stinctive behavior, this link in the development of behavior would 

 seem to appear in the development of the swimming movement as 

 described in the following pages. 



In view of this bearing of the experiments upon the subject of 

 animal behavior certain results of the experimental part of my in- 

 vestigations are here made known before the anatomical phase of 

 the work has been completed. 



Methods. 



The embryos were removed from the egg membranes at various 

 stages in development, ordinarily before they showed any sign of 

 irritability to tactile stimuli. They were then placed in shallow 

 Petri dishes, a single specimen in a dish, and tested from time to 

 time for reactions. Usually an experiment continued until the 

 animal began to swim. 



The stimulus employed was a touch with the end of a rather fine 

 human hair, mounted in such a way as to render the touch very 

 gentle. The extreme sensitiveness of some very young eml)ryos is 

 remarkable. Even the touch of a fine piece of lint will at tiuies 

 evoke a vigorous response, as if it were a violent irritant. 



Without critical consideration the tactile nature of this mode of 

 stimulation might be held in doubt. The touch of a hair such as 

 was used in these investigations might easily cause a considerable 

 pressure, so that there might be a question whether the responses 

 were to a strictly tactile stimulus or to a mechanical stimulus upon 

 the muscles or central nervous system. Indeed, in the very early 

 phase of development, when the irritability was for some reason 

 unusually low, some of the reactions, I believe, may have been to 

 direct pressure upon the muscles or central nervous system. But 

 such instances, if they occurred at all, in these investigations, were, 



'Sherrington, Charles S. "The Integrative Action of tlie Nervous System," 

 p. 8. 



