FISHES OF PENNSYLVANIA, 139 

hard or rocky bottoms; the eggs are small and numerous, and are be- 
heved to be deposited in deep water; Dr. Dall estimates that some indi- 
viduals contain several millions of eggs; in Alaska the eggs are of a 
creamy yellow color, and the fish are found full of spawn from Novem- 
ber to January. From the observations mentioned, it will be seen that 
the spawning period extends at least from November to March, accord- 
ing to Dr. Dall the males are usually much smaller than the females 
and have a smaller liver; in some males he found two or three gall blad- 
ders opening into a common duct, but he never observed this phenom- 
enon in the female; the eggs are laid separate or loose upon the bottom 
of the river. According to Baron Cederstrém, a medium-sized female 
of the European burbot, which is a near relative of the American species, 
contained about 160,000 eggs; in the European burbot, some eggs are 
clear, some yellowish and others almost colorless; the period of incuba- 
tion occupies from three to four weeks; the eyes appear in fifteen or six- 
teen days; the embryos swim by quick movements of the pectorals, 
usually toward the surface of the water, whence they fall passively to the 
bottom. 
The burbot is extremely voracious, and feeds upon bottom fishes and 
crustaceans. It destroys the pike and sucli spiny fishes as the yellow 
perch and sunfish. In Alaskan rivers it feeds upon whitefish, lampreys 
and other species; large stones have sometimes been found in its stomach; 
Mr. Graham took a stone weighing a pound from the stomach of a burbot. 
In the Great Lake region the burbot is considered worthless for food, 
occasionally the livers are eaten; in Lake Winnepiseogee, when caught 
through the ice in winter the fish is highly esteemed; in the fur countries 
the roe is an article of food. On the Yukon river the liver is eaten and 
the flesh is hked by some persons; in Montana the burbot is in great 
demand for food; the quality of the flesh appears to depend chiefly on 
the nature of the habitat of the fish. 
This is the only member of the cod family permanently mesuiTi in 
the fresh waters of America. 
