8 
are required, and thus in her cperations, though there is 
enormous destruction, there 1s no waste. 
Part of this great fact you can demonstrate for your- 
selves. If you will take common water snails, put a few of 
them in an aquarium, and allow them to spawn there, you 
will have at the end of twelve months, provided all goes 
right, hundreds of tiny snails; but if you take half-a-dozen 
of these out soon after being hatched and put them in another 
aquarium, giving them plenty of room, you will find at the 
end of twelve months that they are full-grown specimens. 
Anyone who has kept fish in a parlour aquarium must have 
noticed that the fish do not grow. In the Southport 
Aquarium we were able to observe this matter very fully. 
We obtained a quantity of young turbot about the size of 
the palm of the hand, and placed a number of them in the 
small table tanks, and a further number in the hall tanks, 
these latter tanks being about 1oft. square by 6ft. deep. At 
the end’of a year I was struck with the fact that those we had 
in the table tanks were only the size they were when caught, 
while those in the hall tanks weighed 3 or 4lb. I had some 
of these removed and put in the big tank 3o0ft. long. At 
the end of another year those in the table and hall tanks 
were still about the same size; they had made very little 
srowth; but those in the big tank ranged from 8 to tolb. 
each. At the end of another’ year those in the table and 
hall ‘tanks’ were ‘still stationary, while those in the large 
