170 GEORGE E. NICHOLLS 
ately thin. From this terminal region the fiber is certainly 
absent; the sinus terminalis itself shows signs of disturbance 
and contains the remains of a clot which is certainly not the 
result of the experimental incision, which did not destroy the 
pla mater. 
The specimen must have been one which had been brought in 
recently, probably the previous day, for during my stay at Ply- 
mouth I made use of all the moderately small specimens which 
were available within a very short time of their capture. Since 
in this specimen, the fiber is absent from the region of the sinus 
terminalis and the latter chamber itself is somewhat disrupted 
(for which injury my experiment was not responsible) it is 
almost certain that the ray had been damaged in the trawl, 
probably on the previous day. 
That there was no reaction in evidence when the specimen was 
selected for the experiment is doubtless to be explained by the 
fact that the reaction frequently appears intermittently. More- 
over, the experiment was the last undertaken and was performed 
in some haste so that the usual precaution of keeping the speci- 
men under observation for some hours prior to the operation 
was not taken in this instance. 
The reaction seen in this experiment, therefore, is almost 
certainly to be attributed to an accidental breaking of the fiber 
at some time prior to the experiment and is in no way due to the 
experimental incision which did not disturb the central nervous 
system. 
Two other specimens (3, 49) reveal the fiber broken as the 
result of some accident, but in these cases the snapping of the 
fiber must have taken place in the trunk (or head) region and 
must have occurred only a very short time indeed before the 
operation. 
In the case of the former (no. 3, the subject of the first ex- 
periment performed upon a ray) an overdose of chloroform was 
administered and for some 3 hours following the operation there 
was no sign of returning animation. At the end of that time it 
was decided to discontinue the experiment and the central ner- 
vous system was exposed and hardened. As it happened, this 
experiment, while affording no information upon the function 
