417 
turned upon its side, and the necessary prick inflicted with the point 
of a very fine knife at the appropriate spot. 
The animal was rarely out of the water for so much as thirty 
seconds; recovery was very rapid and there appeared to be no appre- 
ciable shock. None of the specimens died from the effects of the 
operation nor, in the subsequent examination of the tissues by serial 
sections, was there found any indication that morbid conditions had 
been set up. Indeed, apart from certain peculiarities of behaviour 
about to be described, the animals suffered no discoverable ill-effects, 
and were found to feed as freely as is usual for such forms in captivity. 
As the material was to be used later for the investigation of 
problems connected with regeneration, it was necessary that I should 
have specimens killed at fairly frequent intervals. Three separate 
tanks were placed at my disposal and, that the specimens might be 
left as much undisturbed as was possible, the experiments were so 
timed that very few were in progress together, and a tank rarely con- 
tained more than two subjects simultaneously. Further, by so arranging 
that the fish put together were either of different species or markedly 
different in size or colouration, identification was rendered a very 
simple matter and the necessity for attaching tags or marking the 
specimen in any way was altogether avoided. 
The total number of fish upon which the experiment was per- 
formed was eleven, eight of which were skates while the remaining 
three were dogfish. 
Two of these, as already stated, died without recovering from 
the anesthetic. The first, a dogfish (1)*) although living when returned 
to the tank was apparently insensible and was allowed to remain in 
that state for several hours. As it failed to recover several attempts 
were then made to resuscitate it, all of which proved fruitless. It 
was apparently still living when left for the night, but in the morning 
it was found dead and had evidently been so for some hours. Accord- 
ingly it was regarded as useless and was not preserved. 
The second case of the same kind was that of a skate (3) which 
after remaining insensible for between two and three hours was 
removed from the tank and plunged for two or three minutes into a 
mixture of spirit and chloroform to ensure that it was dead. It was 
then eviscerated and the central nervous system largely exposed, the 
dissection being performed under the fixing fluid (aceto-bichromate). 
1) The arabic numerals in brackets () refer to the number of the 
experiment. 
Anat. Anz. Bd, 40. Aufsätze. 27 
