36 SCIENCE SKETCHES. 
median in position. Pectoral fins inserted low. 
Lateral line present. Outline of belly rounded. 
Vertebre in large number, usually about sixty. 
The stomach in all the Saldmonide is siphonal, 
and at the pylorus are many (15 to 200) com- 
paratively large pyloric cceca. The air-bladder 
is large. The eggs are usually much larger than 
in fishes generally, and the ovaries‘are without 
special duct, the ova falling into the cavity of the 
abdomen before exclusion. The large size of the 
eggs, their lack of adhesiveness, and the readi- 
ness with which they may be impregnated, render 
the Salmonide peculiarly adapted for artificial 
culture. 
The Salmonide are peculiar to the North Tem- 
perate and Arctic regions, and within this range 
they are almost equally abundant wherever suitable 
waters occur. Some of the species, especially the 
larger ones, are marine and anadromous, living and 
growing in the sea, and ascending fresh waters to 
spawn. Still others live in running brooks, en- 
tering lakes or the sea when occasion serves, but 
not habitually doing so. Still others are lake 
fishes, approaching the shore or entering brooks 
in the spawning season, at other times retiring to 
waters of considerable depth. Some of them are 
active, voracious, and gamy; while others are com- 
paratively defenceless, and will not take the hook. 
They are divisible into eight easily recognized 
genera, — Coregonus, Plecoglossus, Brachymystax, 
Stenodus, Thymallus, Oncorhynchus, Salmo, and 
Salvelinus. These groups may be discussed in 
order. 
