160 GEORGE E. NICHOLLS 
32. The incision was made at 7 p.m. on August 10. Upon recovery, 
the specimen showed an unusual swimming reaction, then settled down 
with the tail lifted dorsally. It was killed at 7.40 p.m. Duration of 
experiment 40 minutes. 
The sections are practically worthless, merely establishing the fact 
that the incision had severed the terminal filament. 
36. The incision was made at 6.15 p.m., August 15, and was followed 
by a very slight uplifting of the snout. The left pectoral fin was 
also raised. Presently the fish settled normally but later the right 
pectoral was lifted. The specimen attempted to settle upon the tank 
walls but failed to maintain this position. At 7 p.m. the ray appeared 
in no way abnormal and at 7.45 p.m., it was killed. Duration of ex- 
periment 23 hours. 
The fiber was cut, but both free ends seem to be entangled in a 
large clot and there is no evidence that any retraction took place. 
37. The incision was made at 7 p.m. and was followed, almost at 
once, by an elevation of the snout. Like the ray just described, it 
appeared to prefer a vertical position but was unable to maintain 
itself upon the tank walls for any length of time, invariably sliding 
downwards until it was supported by the outwardly (dorsally) bent 
tail (fig. 11). Any reaction affecting the tail, therefore, was masked, 
if it occurred. The ray was killed at 6 p.m. on August 16. Duration 
of experiment 1 day 23 hours. 
In front of the place of the lesion a somewhat limited retraction 
occurred, but the fiber appears to have become caught in an elongated 
clot which extends for some distance*forward along the lumen of the 
central canal. From the anterior end of this clot the fiber emerges as 
a swollen and indistinctly spirally wound thread (fig. 23). 
38. The incision was made at 11 a.m., August 16, but was not fol- 
lowed by any visible reaction. The specimen was killed at 11.45 
a.m. Duration of experiment 45 minutes. 
The tail of this specimen had, at some time, suffered mutilation but 
the wound had completely healed and a secondary sinus terminalis 
had been produced. The experimental incision had severed the fiber 
but the cut ends had not retracted, being held, apparently, by the 
pinching together of the walls of the filum terminale. 
39. The incision was made at 11.15 a.m., August 16 but produced 
no evident reaction. The ray was killed at 5.30 p.m., next day. 
Duration of experiment 1 day 6} hours. 
There was no forward recoil of the fiber from the point where it 
was cut experimentally. During the dissection made to expose the 
spinal cord, however, an accidental cut was made far forward in the 
spinal cord which evidently broke the fiber in that region and it appears 
slack and swollen even as far back as this terminal piece. 
40. The cut, made at 12.15 p.m., August 16, accidentally removed 
the end of the tail (a piece about one-sixteenth of an inch in length). 
The fish took up a vertical position, with the body supported by the 
out-turned tail (cf. no. 30) which, as already pointed out, masks the 
