THE FUNCTION OF REISSNER’S FIBER ans 
ence for the dark corner of its tank and adopted the somewhat un- 
usual action in swimming noted in no. 5 (Raia clavata). During the 
11 succeeding days, it was observed at frequent intervals but was 
apparently normal throughout this period. On July 22 it was killed 
Duration of experiment 13 days +. 
This tail was examined by means of sections cut transversely which 
proved to be quite unsuitable for the purpose of this investigation. 
The fiber is found in the more anterior sections, where it appears not 
markedly swollen and has apparently nearly made good any retraction 
which may have taken place after the operation. 
8. The incision was made at 10 a.m., July 13. By 10.30 a.m. the 
specimen had completely recovered from the anaesthetic and had at- 
tached itself to the (vertical) glass plate forming the front of the 
tank, the tail being lifted slightly and turned to the left. This con- 
dition persisted for an hour or so but by midday the ray appeared nor- 
mal. It was killed at 11 a.m., July 14. Duration of the experiment 
25 hours. 
There was no considerable retraction of the severed ends of the 
fiber, in either direction from the lesion, these being entangled appar-: 
ently, in the clot which occupies the central canal for some distance. 
From this clot the fiber may be traced tautly stretched and:of normal 
diameter. 
10. The incision was made at 11.30 a.m., July 13, and was followed 
very quickly by a marked uplifting of the tail. An hour after the 
operation the ray was found adhering to the wall of the tank with the 
tail swung out dorsally and to the left. The reaction continued to be 
marked during the three following days. By the morning of July 17, 
however, the ray was seen with the tail carried normally and, there- 
after, the specimen appeared normal until July 23 when it was killed. 
Duration of experiment 10 days. 
' For some distance in front of the experimental lesion, the central 
canal is found empty of fiber. The free end of the fiber is found, 
about half an inch in front of the lesion, swollen and thrown into a 
loose tangle (fig. 26), from the anterior end of which the fiber emerges 
much less swollen and fairly straight. No part of the fiber shows any 
trace of spiral twisting. 
11. The incision was made at 10a.m., July 20, with a fine knife from 
the right side, care being taken not to penetrate completely through 
the tail. The usual reaction did not appear, but there was some dis- 
placement of the right pectoral fin which was brought up sharply 
dorsally. Next morning the ray appeared entirely normal. Itwas 
killed at 4 p.m., July 22. Duration of experiment 2 days 6 hours. 
The sections show that the incision missed the filum terminale and 
the fiber, therefore, remained unbroken. 
19. The incision was made at 4.10 p.m., August 2. The specimen 
was kept under observation until it was killed on August 9 but during 
the whole of this time nothing unusual in its behavior was noted. 
Duration of experiment 6 days 20 hours. 
