138 GEORGE E. NICHOLLS 
my precautions, two of the subjects of the experimentis subse- 
quently failed to recover from the anaesthetic. 
Finally it was found that a short immersion of the specimen 
in. sea-water in which had been shaken up a small quantity of a 
mixture of chloroform and ether would induce a sufficient de- 
eree of insensibility, and this method was adopted throughout 
my series of experiments in 1911. Under this treatment, none 
of the specimens died. 
The operation was quite easily pertormed, the subject being 
removed from the chloroform water and placed upon the table 
with its tail turned upon the side. The necessary prick was 
inflicted with the point of a very fine scalpel (which had pre- 
viously been sterilized by passing through a gas flame) at a 
point usually considerably less than a third of an inch in front 
of the sinus terminalis. In the dogfish, therefore, the incision 
perforated the caudal fin near its hinder border while in the 
rays the cut was generally made behind the last dorsal fin (figs. 
2, 8). The animal was at once returned to its tank, having 
been out of water for, perhaps, thirty seconds. Recovery was 
usually rapid and, as might be expected, there was no evidence 
of shock. 
None of the specimens died from the effect of the operation, 
nor in the subsequent examination of the tissues in serial sec- 
tions, was there found any indication that morbid or sepiic 
conditions had been set up. Indeed, apart from certain pecu- 
liarities of behavior about to be described, and which I attribute 
to the breaking of Reissner’s fiber, the animals suffered no ap- 
parent ill-effects. 
Nevertheless, two or three specimens were lost during the 
progress of the experiments from causes indirectly connected 
with the experiments. In the second series of experiments a 
number of photographs were taken, of normal specimens as 
well as of the subjects of the experiments. I could find no record 
of previous attempts to photograph living fish, and had accord- 
ingly to make a number of trial exposures. At first, attempts 
were made to obtain the photographs out of doors by daylight. 
Numerous difficulties cropped up however, for none of the out- 
