Aquatic Lite 73 
again living free at the bottom, and the 
green  sea-lettuce (Ulva _ latissima) 
buoyed with bits of cork to cover two- 
thirds of the surface and allowed to hang 
down ten inches from the top on the side 
of the jar nearest the light. The animals 
ANS S 
Northern white coral (colonies rang- 
ing in size from 2 to 6 inches in diame- 
ter). 
Brown anemones (3 or 4). 
White anemones (3 or 4). 
Tunicates (Molgula) (3 or 4). 
Killifishes, 2 inches long (2 or 3). 
Variegated minnows, 2 inches long (2 
OF 8). 
Prawns, 1% inches long (2 or 3). 
Young eels, 3 or 4 inches long (1 or 
25) 
ud snails (Nassa obsoleta) (1 to 12). 
Owesier (i). 
Little-neck clam (J’enus mercenaria) 
(it). 
Warning has been given the beginner 
by some aquarists to limit his animals one 
to the gallon of water. It can be seen 
from the list just given that a gallon will 
accommodate more than one animal— 
even more than four—but in experiments 
with marine aquaria too much modera- 
tion cannot be urged at the start. 
Sea-lettuce is absolutely essential for 
the balanced aquarium. Other plants 
may be used with it, as the red alga called 
“Flame weed” (Grinella americana) ; 
end dead, sun-dried hydroids such as 
Sertularia argentea and S. pinnata, make 
good ornamental effects. 
Other animals which can be success- 
fully confined in balanced aquaria are 
small mussels—say a quarter of an inch 
in length, rock barnacles, annelids (espe- 
cially the tube dwellers), and very small 
crabs. Large crabs tear the plants and 
catch the fishes, but small specimens of 
the mud and spider crabs one-half inch 
or so in diameter, are interesting (crabs 
being truly comical animals) and desir- 
able, for they pick up scraps from the 
bottom; and the small hermit crabs are 
especially good scavengers. 
It is well to place an inch or two of 
fine pebbles, white sand, or bird gravel on 
the bottom of the jar, and a few stones 
must be added for the attachment of 
anemones, and for the crabs to hide 
under. Care must be taken to wash the 
sand thoroughly. Bird gravel is very 
dirty, and will ruin the aquarium if put 
in before cleansing. 
Hermit crabs should be provided with 
empty shells of a suitable size, so that 
when they outgrow the home they are 
living in and go house hunting for a large 
one, the new dwelling will be at hand. 
They are pugnacious, and two will fight 
hard for the possession of a desired 
shell. 
Little-neck clams and oysters, whose 
siphons are always busy, are valuable as 
clarifiers. 
Snails which consume vegetation are to 
be guarded against. The periwinkles do 
not thrive so well in standing water, but 
no balanced aquarium is complete with- 
out a few mud snails (Nassa obsoleta). 
These do not harm the vegetation appre- 
ciably, preferring animal food, and _ be- 
sides being excellent scavengers, are al- 
ways interesting to watch, with their long 
inquisitive siphons traveling on before 
like an elephant’s trunk, and specimens 
are often seen carrying around a little 
roof garden of minute green plants, an 
occasional snail being so thickly covered 
with the fine marine alga known as 
Enteromorpha that it might be mistaken 
at first glance for a sea mouse. ‘The mud 
snail, found all the way from Massachu- 
setts to Florida, is the commonest of 
smali Atlantic Coast mollusks. 
Young specimens of starfishes may be 
