DR. DAVY ON THE TORPEDO. 539 



and moving about actively. They imparted smart shocks to the fingers or finger 

 pressing the upper surface, and another of the same hand the under surface of the 

 electrical organ : they distinctly affected the galvanometer, and feebly magnetized 

 needles through the medium of a spiral. These trials were made at 2 p.m. At 10 p.m. 

 all the fish were alive and vivacious ; an hoar after I found them all dead. 



The third fish I have to notice was a Tremola, seventeen inches long and twelve 

 and a quarter broad. When brought, on the evening of the 6th of November, in a 

 vessel of salt water, soon after it had been caught, it was tolerably vivacious ; yet it 

 did not affect the galvanometer. Before it was quite dead, the abdomen was opened, 

 and the foetal fish were extracted. They were ten in number, all of them about the 

 same size. In all of them the outer yolk-bag had disappeared, as represented in 

 Plate XXIII. figg. 2, 3, 4. Touching them with the hand, in the act of removing them 

 from the uterine cavity, I received a distinct shock, sharp though not strong. Put 

 into fresh sea-water, as they were extracted, some of them immediately, and in a few 

 seconds all of them, were active and swam about : and making trial of one of them 

 instantly, (the apparatus being in readiness,) it powerfully affected the galvanome- 

 ter, and made a needle slightly magnetic. To ascertain the state of the internal yolk- 

 vesicle, one of these fish was killed by putting it into fresh water, about half an hour 

 after its extraction. It immediately became very restless, and endeavoured to escape : 

 then, in less than a minute, it became quiet, and its water-valves ceased to act. Two 

 or three times, at intervals, it was again restless : in about twenty minutes it was 

 motionless and dead *. The appearance of its internal yolk-vesicle is represented in 

 Plate XXIII. fig. 3. 



Three of these fish remained alive till the 22nd of May, in sea water, which was 

 changed daily, or every second day. Of the others, one only died a natural death ; 

 the rest were killed at intervals, for the purpose of examining the size of the internal 

 yolk-vesicle, which very slowly diminished during this period, and, as well as I could 

 judge, in a very regular manner ; supposing, when first extracted, that in all, the 

 internal yolk was nearly of the same size. Plate XXIV. fig. 1. shows the diminution 

 it had undergone on the 22nd of May, when the three residual fish died, apparently 

 from the carelessness of a servant giving them turbid salt water, and weaker in salt 

 than they had been accustomed to. 



During the whole of this period of five months and more, they ate nothing, though 

 very small fish, both dead and alive, were put into the water. They retained, and 

 indeed increased in activity, and even in their electrical energies, of which I made 



out through the branchial apertures, but occasionally is discharged (the latter being closed) in considerable 

 quantity through the superior apertures. Block erroneously supposes that these latter are the normal outlets. 

 He says, " lis servent k I'animal k rejetter I'eau qu'il avale, soit en prenantsaproie, soit celle qui entre par I'ou- 

 verture des ouies." — Histoire Naturelle des Poissons, torn. iii. p. 667. 



* Is it found in the Nile, as asserted by some authors ? The above fact would seem to indicate that the 

 Torpedo cannot exist in fresh water. 



