
NOTES FROM THE MUSEUMS AND THE AQUARIUM. 25 
The most critical time for the young trout after hatching, is the period 
immediately following the absorption of the yolk-sac, when the young fish 
is entirely thrown upon its own exertions for its food supply. At this 
period the mortality in our tanks has heretofore always been high. This 
year, however, the young trout were, immediately after the complete 
absorption of the yolk-sac, removed from the hatchery to a couple of tanks, 
about 18 inches in depth, having a constant stream of fresh-water flowing 
through them. There they have been supplied regularly with sheep’s 
liver-meal, prepared by boiling, thoroughly desicating and pounding the 
liver, and then passing it through a fine sieve. From the first the young 
trout, even the smallest and weakest, began to feed eagerly on this finely 
powdered material. It remains suspended in the water, without becoming 
saturated, and is carried round by the currents in the tank until such 
portions of it, as are not consumed, are carried finally away by the over- 
flow pipes, and thus the accumulation of decaying remnants—which so 
often settles down at the bottom, and which is always a source of the 
greatest danger to young trout on account of their great susceptibility to 
infection from fungoid diseases—is prevented. To these arrangements and 
to this method of feeding we attribute our successful rearing, this year, of 
so large a proportion of Salmo irideus. 
Malapterurus electricus.—Numerous specimens of this interesting 
fish have now been alive in the Aquarium tanks, during the past two years. 
The great difficulty in obtaining specimens lies in their transportation. 
Being inhabitants of fresh water, and of a tropical climate, they require 
special attention as the ship in which they are being brought approaches 
our latitude, as well as frequent changes of pure and well aerated water, 
which is not always to be obtained from a ship’s tanks. Thanks, however, 
to the indefatigable care and attention, kept up for the many weeks of the long 
voyage from West Africa, by Mr. A. Ridyard, the chief engineer of the 
‘Niger,’ one of Messrs. Elder, Dempster & Co.’s large fleet of steamers, we 
have had a regular supply of Electric-fishes in the Aquarium during all that 
time. We have gratefully to acknowledge the lively interest taken by Mr. 
A. L. Jones, and the other members of the firm, who have most liberally 
carried, freight free, anything coming for the Museums, and given every 
encouragement to the officers of their vessels to aid the Institution whenever 
it has been possible compatibly with the exigencies of the service. 
The water in the Malapterwrus-tanks has been changed every day and 
maintained, day and night, at an even temperature of between 70° and 
80°F. When in good health the Electric Cat-fish lies sluggishly on the 
bottom, rising to the surface only when in expectation of being fed. They 
thrive well on, and take with avidity common earth worms, boiled liver 
chopped up, and occasionally a young trout (Salmo, sp.), from 2 to 3 inches 
in length, from those being reared in the Aquarium. 
The fish has small sparkling, diamond-point like eyes, which it apparently 
uses very little ; and it is probable, indeed, that their vision is limited or 
defective, for their optic nerve is extremely attenuated, when compared with 
that in other fishes of corresponding size. If a worm be dropped into the 
tank to fall wriggling to the bottom, the Malapterwrus rarely, if ever, sees 
it. A few moments, however, after the worm has fallen through the water, 
the fish becomes suddenly agitated, apparently through its olfactory organ, 
or, perhaps, by its barbels detecting the undulations communicated to 
the water ; and begins turning rapidly about with tensely extended and 
vibrating barbels, keenly quartering out the tank in quest of the quarry, 
' whose presence it has become sensible of. The sought-for object is, 
however, as a rule, discovered without its coming into actual contact with 
