150 GEORGE E. NICHOLLS 
noticed on several previous occasions. This specimen, then, gave a 
marked reaction lasting for 13 days. Duration of the experiment 16 
days +. 
The sections showed that, in front of the incision, a secondary sinus 
terminalis had been produced into which Reissner’s fiber is seen to ex- 
tend and, in contact with the hinder (meningeal) wall of which, it 
flares. Apparently it has just become attached thereto (fig. 31). 
Behind the incision the fiber has apparently entirely disappeared. 
9. This specimen, for nearly a week after the operation (performed 
on July 12), showed a curious restlessness, not once being observed at 
rest until the morning (10 a.m.) of July 18. This activity was fol- 
lowed by an equally marked lethargy. The specimen took up a posi- 
tion in the darkest corner of the tank, where it lay with the body 
bent upon itself at-a sharp angle and the tail supported against the 
sloping part of the tank. Not until July 22 was the specimen seen, in 
repose, away from the wall of the tank when it was found resting with 
the end of the tail slightly lifted: the flexure of the body was nearly — 
straightened out. It was killed on July 23 the experiment having 
lasted 11 days. 
In the sections the fiber (in front of the lesion) is found to extend 
backwards nearly to the place where the filum terminale was severed. 
It is probable, therefore, that the fiber had nearly recovered from the 
effect of the operation but the experiment was ruined by an accidental 
cut made, far forward in the trunk region, when exposing the spinal 
cord. The fiber in the piece examined is much swollen and continu- 
ously twisted (text-fig. 2), undoubtedly due to a (backward) re- 
traction from this distant cut. 
20. The incision was made at 11.15 a.m. on August 3, 1911, and, by 
noon, the tail was lifted slightly so that the lower border of the caudal 
fin no longer rested upon the tank floor. When disturbed, the fish 
swam with a quick wriggling action (cf. 2) and came to rest in a curi- 
ous attitude in a corner of the tank, the anterior part of the trunk 
being poised vertically, supported by the adjacent walls of the tank, 
while the posterior part lay out horizontally upon the tank floor (cf. the 
ray, fig. 11). After being again disturbed, it once more came to rest 
in this peculiar attitude and so remained until 3 p.m. at which time 
it was again compelled to move. It was observed to swim in quick 
rushes, even leaping partly out of the water, and the wriggling move- 
ment was very noticeable. Ten minutes later it had settled down 
with the end of the tail slightly lifted but resting lightly against the 
tank wall. It was disturbed yet again and was subsequently induced 
to settle well away from the walls of the tank and the tail was then 
seen to be held at least an inch and a half from the floor, and it con- 
tinued in this attitude until 4.15 p.m. when it was accidentally dis- 
turbed. During the next half hour it was repeatedly set in motion 
by the movements of another dogfish which shared the tank. It 
settled down six several times in the same attitude (with head and tail 
lifted) once or twice essaying the half vertical position which it had 
