THE FUNCTION OF REISSNER’S FIBER Laz 
The tail had clearly been truncated earlier in life but had com- 
pletely healed and a secondary sinus terminalis had been formed. 
The experimental cut failed to break the fiber which is seen of normal 
size and tautly stretched. 
52.°The incision was made at noon and was followed by a scarcely 
perceptible reaction. The ray was killed at 3.30 p.m. Duration of 
experiment 33 hours. 
The fiber was severed by the incision but the free ends, which are 
slightly knobbed and swollen are entangled in a clot and thus, presum- 
ably, retraction has been prevented. 
53. The incision was made at 12.05 p.m. and was quickly followed by 
a fairly definite reaction which, however, was not evident at 2.30 p.m. 
when the specimen was killed. Duration of experiment 25 hours. 
The fiber is seen cut and slightly slackened but the free ends have 
been withdrawn only for a short distance from the lesion. 
62. The incision was made at 8.30 p.m., August 21, and was seen 
to be followed by a marked swimming reaction but the specimen was 
not seen in repose, after the operation. It was killed at 10.30 p.m. 
Duration of experiment 2 hours. 
The sections are poor but serve to show that the filum terminale 
was cut. No fiber can be made out in such parts of the central canal 
as I have been able to examine. It is probable that the fiber has re- 
tracted forward, beyond the anterior limit of the piece of tissue 
sectioned. 
63. The incision was made at 11.10 a.m., August 22, and was fol- 
lowed by a marked swimming reaction. At 11.40 a.m. it settled down 
but the tail was not displaced. It was killed immediately. Duration 
of experiment 30 minutes. 
The fiber had been cut and had, apparently, retracted forwardly, 
completely from the filum terminale in the piece of tail examined. 
66. The incision was made at 11.35 a.m. and was followed by a 
marked reaction. The ray was killed at 12.20 pm. Duration of 
experiment 45 minutes. 
The fiber was cut and had retracted some distance forward. In 
the sections it may be seen lying slackly in an undulating course but 
is not appreciably swollen. 
C. Raia clavata 
5. The incision was made at 10 a.m., July 8. By 5 p.m. the hinder 
part of the tail was seen to be lifted and this reaction was manifested 
throughout the evening and became still more marked next day. On 
July 11, the specimen appeared very lethargic and, on every occasion 
after being disturbed, returned to rest in the darkest part of its tank. 
In swimming, the specimen would remain poised nearly vertically, 
with a curious hovering movement, for 10 minutes or more at a time, 
its tail being turned sharply dorsally. At rest, so far as could be seen, 
the tail was disposed normally, but next day it was held uplifted for 
