TROPICAL AQUARIUM FISHES 95 
ture as that in the aquarium, which should be of an uniform summer 
heat. Keep no other fish with Cichlids. 
B6 GROUP 
THE GOBY GROUP (Gobiide). These include bottom fish from 
all over the world, occurring in shallow streams or shallow shore-waters— 
marine, brackish and fresh. Little is known of their spawning habits, 
beyond the fact that some spawn among—-and on—the stones on the 
bottom. Others—small species—will spawn on the inside—i. e., concave 
side—of a piece of drain pipe laid on its side in the aquarium and others 
spawn among the weeds (roots) on the sand or mud. Some protect 
their spawn. Others do so but little if at all. Among the Gobiide are 
our well-known “Darters’—familiar to the country schoolboy—also 
the “Miller’s Thumb,” “Tommy Cod” or “Sculpin” (Cottus ictalops, 
Rafinesque) and the most peculiar “Mud-Springer” (Periopthalmus 
koelreuteri) from the Tropical Tide-waters of Africa and Asia. Shallow 
water is a prime requisite for these fish, the last named species requiring 
stones projecting above the water, sloping up gradually, upon which the 
fish likes to climb out of water and “bask.” As to rearing the young, 
aquarists must experiment and persevere, as very few have had much 
success with them and those who have reared any have been European 
aquarists with abundant time and patience. 
B7 GROUP 
LABYRINTH FISH (possessed of an air-cavity or cell beneath 
each gill-cover, in which a supply of air is stored for breathing). These 
fish are all air-breathers, coming frequently to the surface to replenish the 
air in the “storage chamber.”” Most of the Labyrinth fish build “bubble 
nests”, i. e., secrete a “glue” in their mouths, and blow air-bubbles 
coated with this glue, which float in a mass and in which the male 
places the eggs, immediately after fertilization, which takes place in 
mid-water, the parent fish intertwining their bodies immediately under 
the nest of bubbles at frequent intervals, extruding a few eggs at a time. 
Then as the fish relax their embrace, the male catches the eggs in his 
mouth and blows them—each one separately—into the air-bubble nest. 
As soon as all the eggs have been extruded from the female and 
fertilized in the external embrace of the parent fish, the male having 
gathered all eggs into the floating nest, he then drives the female to as 
distant a corner of the aquarium as possible (as he knows that she will 
eat the eggs if she gets a chance) and for about 36 hours the male fish 
guards the nest and eggs and re-arranges the eggs and adds more bubbles 
where required. Towards the end of the hatching process, the male 
spreads the nest out as much as possible, to give the hatching young as 
