a 
seventh day, however, it was found in a corner of the tank at rest, 
with its body and tail bent in a sharp curve and the end of the tail 
supported on the sloping surface where the floor of the tank passed 
into the wall. The curvature of the body was here a simple one with 
the tail swung sharply to the right, whereas in the other specimen (2) 
the curve was a meandering one and the tail lay out to the left. By 
the tenth day the trunk had become straight and the curvature was 
localized in the tail, which was now bent markedly to the left. Not 
until the eleventh day would it come to rest except in the corner, but 
upon that day it was observed lying well out in the tank and it was 
seen that “the tail was lifted quite free of the floor. It was still in 
that condition when, on the next day, it was killed. 
During the whole time that the experiments were in progress a 
close watch was kept upon the specimens in the aquarium, chiefly 
that the behaviour of many, presumably normal, specimens might be 
observed both in action and in repose. Upon July 15th a large 
Scyllium canicula was seen with its tail lifted well free of the gravelly 
bed of the aquarium. The same specimen was noticed again and again 
and finally about a week later it was captured. Upon close examination 
it was discovered that the upper lobe of the caudal fin was not quite 
complete, a narrow strip of skin from its hinder border having been 
removed, so that the free ends of the dermal fin rays could be seen 
projecting freely1). The fish, which measured twenty-five inches in 
length and had been in captivity for some time, was then removed to 
one of the tanks in the laboratory where it could be kept under ob- 
servation more easily and is the specimen (F) referred to below. 
It was found that when at rest it invariably kept the tail slightly 
lifted and when disturbed swam with a wriggling movement that had 
also been remarked in specimen (2), while on settling down again the 
tail rested for a few moments horizontally and was then slowly lifted. 
After being kept under close observation for two days it was killed 
and the entire central nervous system preserved. The examination 
of the hinder part of the spinal cord which was afterwards made by 
means of serial sections proved indisputably that the fibre of REISSNER 
had been accidentally broken in life, and it was found lying in loose 
undulations in the canalis centralis, extending nearly to the broken end 
of the filum terminale, as shown in the photomicrograph reproduced 
(Pr Bigs IR f:). 
1) It is probable that the tail of this specimen had been pinched 
by the trawl. 
