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. It 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 wall 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, Brachiomcs ruhens, some- 

 times occurs so thickly that the surface of the water appears to be covered 



