The Reaction to Tactile Stimuli 
245 
where the two curves 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 
descriptions, 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 upon the basis of completeness of the record and 
duration of the experiment. Owing to the difficulties in the manip- 
ulation of the work and unavoidable hindrances many experi- 
ments 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, cannot, on 
that account, be included in a comparative study of this kind. 
The several columns in this tabulation have significance as follows : 
Column A. The number of the experiment, the data of which 
read to the right. 
Column B. The time that elapsed between the last trial which 
gave no response and the first to which response occurred. 
Column C. The time during which the embryo was asymmetri- 
cal in response. 
Column D. The interval or time that elapsed between the last 
observed response that accorded with asymmetry and the first re- 
sponse that accorded with irregularity. 
Column E. This is the second phase in the development of em- 
bryos of Type III, and the first phase of embryos of Type II. It is 
described above as the period of irregularity in response. 
Column F. The interval or time that elapsed between the last 
observed reaction that accorded with irregularity and the first that 
accorded with the regular form of response as described above for 
Type 1. 
