CoGHli.L, The Reaction to Tactile Stimuli. 87 



tions of the reaction according to written descriptions made at the 

 time of trial. They can not be considered as absolutely accurate 

 in every detail, but they do represent truthfully the general order 

 of the development of trunk movements in these animals. 



The curves of the charts represent the side touched and the 

 direction of the initial movement in the reaction relative to the 

 side touched. The solid line records the direction of the movement 

 of the head; divergence to the left from the vertical records a 

 movement toward the side touched ; divergence towards the right, 

 away from the side touched ; conincidence with the vertical, undeter- 

 mined. The broken line records the side touched; divergence to 

 the left signifies a touch on the left side of the head ; divergence to 

 the right, a touch on the right side ; a blank, no record. Obviously, 

 where the two cur\'es are parallel the movement recorded was to the 

 left; where they diverge or converge the recorded movement was 

 towards the right. 



The apparent incompleteness in the serial numbers of the trials 

 in the first column of some charts is due to the fact that in these ex- 

 periments alternate or occasional trials were being made with refer- 

 ence to touch on the tail bud. The charts represent perfect series 

 of trials with reference to touch on the side of the head. 



The charts presented here are selected from a series which, with 

 descriptioins, has been deposited with the Wistar Institute of Anat- 

 omy and Biology, for the advantage of students who may be inter- 

 ested in a more exhaustive report of my experiments than this paper 

 affords. 



The accompanying table presents schematically some of the data 

 upon which this classification into three types is based. It is the 

 tabulation of the records of 36 specimens which have been selected 

 solely uj)on the basis of completeness of the record and duration 

 of the experiment. Owing to the difficulties in the manipulation 

 of the work and unavoidable hindrances many experiments were 

 not carried continuously through the entire period which is here 

 under consideration, and, although contributing materially to the 

 evidence on the problem as a whole, can not, on that account, be in- 

 cluded in a comparative study of this kind. 



