420 
was raised in the middle line forming a very distinct arch. This 
transverse folding was accentuated by the upturning of the margin of 
the pectoral fins. For fully five hours after the operation was per- 
formed this attitude was maintained and then the trunk slowly settled 
down into the normal position. The uplifting of the tail with its 
curvature towards the left persisted, becoming intermittent, but was 
still to be observed upon the fourth day. 
As already mentioned, the reaction was associated with abnormal 
lethargy, and many of the specimens would not bestir themselves for 
hours together, unless disturbed. Then they would swim, often poised 
almost vertically, with a curious hovering movement, maintaining this 
attitude not infrequently for so long as from ten to twenty minutes. 
On settling down again, whether in a vertical pose against the tank 
wall or horizontally upon its floor, the tail would lie for a few moments 
normally. Then, with a movement so gradual as to be almost imper- 
ceptible, the tail would drift upwards and to one side into the cha- 
racteristic position. 
One skate alone (11) failed to react in the usual way, but instead 
the outer flexible part of the right pectoral fin was held up at a 
slope nearly approaching the vertical and was kept in this position 
during the remainder of the day of the operation. By the following 
morning the fin had settled down and the fish had apparently become 
normal. 
In the control specimens the same vertical pose in swimming was 
not infrequently assumed, but it rarely lasted for so long as five 
minutes and was generally adopted if the fish had encountered some 
obstacle which it endeavoured vainly to surmount. 
The blundering of the animal into the sides of the tank and other 
bodies which was recorded by SARGENT (1904) as a marked reaction 
to be observed in the specimens upon which he had operated, is, I 
believe, simply a result of the transference of the specimens to new 
(and more confined) quarters. In most cases, my specimens (both for 
control and those actually operated upon) had been removed from the 
much more spacious tanks of the aquarium, while a few were freshly 
taken from the sea and, during the progress of the experiments, all 
were kept in comparatively confined quarters in tanks in the laboratory. 
All the specimens (dogfish as well as skates) rushed about wildly 
when first put into the small tanks and frequently collided with the 
bounding walls or other fixed structures (such as the outlet pipe), 
and this was true equally of the control specimens and of the actual 
subjects of the experiments. It became, however, an occurrence of 
