TROPICAL AQUARIUM FISHES 57 
The development of the embryo under the microscope is plainly 
observable and is extremely interesting. The hatching time is from 
three to fourteen days, according to temperature.’ At a temperature 
ranging from 70 to 75 degrees Fahrenheit they should take from four to 
five days. This is considered to produce stronger fish than a slow hatch- 
ing. The hatching trays and young fish should be kept in a light place 
and, if possible, where they may be protected from a temperature below 
60 degrees. Goldfish at any age should be partially protected from the 
direct glare of the sun, so that they may at will go into the sun or shade. 
A few sticks to form a rough lattice over the tray or tub will do very 
well. In case of rain the sticks, unless already weatherbeaten, should be 
removed, as water from new wood is injurious. If the fish are in a 
position where they get only about two hours of morning sun, no pro- 
tection from light need be considered. Goldfish do’ not prosper in too 
much heat, and temperatures above 85 degrees, even temporarily, are to 
be avoided if possible. Fish under eight weeks old can stand more heat 
than can older fish. 
When the alevin or newly hatched embryo bursts from the egg it is 
a very weak creature. Jt appears a mere thread with a pair of eyes at 
one end and small lump in the centre. This is the umbilical sack and 
serves as subsistence for the first few days. At first the alevin can only 
swim by a few jerky motions, and has the power of sticking wherever it 
touches. At the age of one day they are to be found hanging on the 
plants and the sides of whatever receptacle they are in. In from two to 
three days they are swimming freely. When the umbilical sac has been 
absorbed, which is in about three days, the babies will need some food 
which has been previously prepared. The first natural food is a large 
variety of microscopic animals known under the general heading of 
infusoria. These are present in all exposed water which has stood a few 
days, but in order to have sufficient for fishfood it is necessary to have 
conditions favorable to their culture. This consists mainly of vegetable 
decay. Dried and powdered lettuce leaves or duckweed, sprinkled 
thickly on the water produce good results in a few days, kept in a warm 
place and a subdued light. Also a quantity of hay over which boiling 
water is poured will soon produce the creatures. A low-power micros- 
cope or cheap magnifying glass should be employed in this work. (See 
page 140). After the culture is apparent and the fish are swimming 
freely, occasional dips of culture water should be put in with the young 
fry. Sometimes the infusorians can be found freely in standing pools, 
particularly where the water is not very clean, and where there are no 
daphnia or other crustaceans. One species, Brachionus rubens, some- 
times occurs so thickly that the surface of the water appears to be covered 
