244 
G. E, Coghill 
Type 11. Embryos which for a relatively short period at first 
respond irregularly with movements of the head toward or away 
from the side touched, and then enter upon a relatively long period 
of response like that of Type L 
Type IIL Embryos which are at first asymmetrical in response, 
that is to say, they move their head in one direction only, regardless 
of the side touched, and then enter upon a short period of irregu- 
larity like the first period of Type II, and finally upon a relatively 
long period of response like that of Type 1. Or individuals of 
this type may pass directly from the period of asymmetry to the 
regular form of Type 1. The accompanying charts illustrate the 
behavior of typical specimens from each of these three types. The 
first column on the left in these charts records the serial number of 
the trials made, and the record of each trial is represented in the 
corresponding horizontal line to the right. The figures in the 
second column from the left record the time in hours and minutes 
that elapsed since the last preceding trial in each case. The dia- 
grams in the third column from the left represent the form of reac- 
tion in the various trials. Where there is more than one diagram 
in a space these are to be read from lefr to right, and each represents 
a distinct phase in a series of movements. The arrow occasionally 
placed in these spaces indicates that a cephalo-caudal progression 
of the movement was distinctly observed. Where an occurs 
the specimen swam, and the following diagram in the same space 
indicates the composition of the swimming movement. It should 
be noted that these diagrams of the movements are simply free- 
hand representations of the reaction according to written descrip- 
tions made at the time of trial. They cannot 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 move- 
ment 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; coincidence 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, 
