PLATE 1 
EXPLANATION OF FIGURES 
1 Seyllium ecanicula. A photograph of a normal specimen upon which no 
experiment had been performed. The lower border of the caudal fin is seen 
lightly resting upon the floor of the tank. 
2 <A photograph of the subject of experiment 22, taken nearly five hours after 
the operation, showing a moderate reaction. *, indicates the region of the 
incision. 
3 A photograph of the same dogfish, taken half an hour later, the tail being 
rather more lifted. 
4 A photograph of the subject of experiment 34, taken about two hours 
after the operation, showing a well marked reaction. 
5 <A photograph of the subject of experiment 24, taken upon the third day 
of the experiment, and showing a well marked reaction of the tail. 
6 A photograph of the subject of experiment 23, the specimen being seen re- 
posing in the attitude adopted by normal dogfish. The photograph was taken 
upon the fourth day of the experiment, no reaction having appeared. 
192 
