158 GEORGE E. NICHOLLS 
several hours. On July 13, the tail was seen turned to one side and 
supported upon the side of the tank, the animal being very sluggish. 
Next morning, appearing normal, it was killed. In this case, then, 
the reaction appeared about 6 hours after the operation, was exhibited 
continuously for 24 hours and intermittently during the three following 
days. Duration of experiment 6 days. 
In this case the tail piece was cut transversely, which sections it 
was found are quite unsuitable. Behind the incision, the fiber seems 
to have largely withdrawn into the sinus terminalis in which a coiled 
mass can be recognized. In front of the lesion, the fiber, somewhat 
swollen and lying unevenly (fig. 24), appears to extend backwards 
almost to the point where it had been broken. 
6. The incision made at 9 a.m., July 9, was followed very quickly 
by an uplifting of the tail which amounted to as much as 23 inches or 
even 3 inches from the tank floor (the specimen being only 9 inches 
in length). The head was also raised, the tip of the snout being lifted 
at least 1 inch, so that the long axis was very markedly curved. In 
addition, there was a transverse flexure of the body, the lateral borders 
of both pectoral fins being sharply upturned, also. By 2.30 p.m., the 
trunk had become flattened and the ray had settled down normally 
excepting that the tail was still raised and at a sharp angle to one 
side. Next day the tail had resumed its normal (horizontal) position. 
In its marked lethargy and in adopting an unusual attitude in swim- 
ming (when disturbed) it resembled the preceding specimen (5). On 
July 12, at 10 a.m., the tail was again seen to be well raised: disturbed, 
the specimen would rise to the surface and float in a nearly vertical 
position for-as many as 20 minutes at a time. On each occasion, it 
returned to a vertical position of rest. On July 13, it was observed 
at rest upon the floor of the tank with its tail displaced to one side 
(the right) but horizontal. Next day it appeared normal and, dur- 
ing the morning, was killed. In this instance, there was a well marked 
reaction manifested almost immediately after the operation and con- 
tinuing for 24 hours or so but thereafter only appearing intermit- 
tently. Duration of experiment 5 days +. 
The sections are quite unsatisfactory. Behind the lesion, the fiber 
appears to have been caught by the pinching together of the walls of 
the filum terminale and has not retracted. In front of the region of 
the incision, however, the fiber has been withdrawn forward out of the 
terminal piece sectioned. Sections were prepared of the penultimate 
piece and these revealed a very delicate filament lying slackly near the 
anterior end of this piece. 
15. The incision was made on August 2, at noon, the needle being 
thrust into the very extremity of the tail. There was no reaction and. 
the ray was killed at 7.30 p.m. Duration of experiment 75 hours. 
In this specimen the sinus terminalis does not extend downward 
behind the notochord but lies wholly dorsal to that structure. The 
cut, therefore, failed to penetrate the sinus terminalis and the fiber 
was undamaged. 
