419 
Skates appear normally, in captivity at any rate, to be rather inactive, 
but in the specimens operated upon this lethargic condition was very 
pronounced. They retired to the darkest part of their tank and moved 
very little unless they were roused. The control specimens were more 
active but when at rest were observed to have settled down apparently 
quite indifferently upon any part of the tank. 
It was in most cases within an hour or so of the onset of this 
lethargy and, therefore, well within a couple of hours of the operation, 
that the characteristic reaction first appeared. 
In normal specimens at rest, the tail is practically invariably, so 
far as my observations go, extended in a straight line which is the 
continuation of the long axis of the body. If the control specimen 
be resting upon the floor of the tank its tail lies horizontally. Upon 
the rocky uneven floor of the aquarium the horizontal level is main- 
tained, so that when in such a position the tail stands out unsupported 
there is neither a drooping nor an elevation of the tail. If, as fre- 
quently happens, the skate adheres to a vertical surface the tail will 
hang vertically. 
In the case of six out of seven skates in which Reıssner’s fibre 
had been severed all this was altered. Generally speaking, within 
a couple of hours of the operation the whole tail was found to be 
curved sharply dorsalward at a considerable angle to the line of the 
long axis of the body. It was also often deflected well to one side, 
but the duration of the reaction varied enormously. In most cases it 
lasted almost continuously for about twenty-four hours, but in one 
case (8) it lasted barely an hour, while in others (5, 6 and 9) it continued 
intermittently during the second, third and even into the fourth day. 
In (8) not only was the reaction of very short duration but it 
was also so very slightly marked that my record of the experiment, 
made at the time, contained a note to the effect that the incision, 
which was made very far back, would probably prove to have failed 
to break the fibre. The real explanation will be deferred to the next 
section, in which the results of the examination of the material under 
the microscope will be described and discussed. 
In (6) on the other hand, the reaction was very pronounced. This 
specimen, which was asmall Raja clavata (about nine inches in length), 
maintained the uplifted condition of the tail for hours together, the 
extremity being raised between two and three inches from the floor 
of the tank. Not only so but the snout was also raised at least an 
inch, the curvature of the long axis of the body thus being very striking. 
Further, there was a decided transverse curvature of the body which 
27* 
