CODS. 
465 
they sometimes choose to enter fresh water". Strictly 
speaking, we can hardly call them deep-sea fishes; but 
some species descend to a depth of at least 500 or 600 
metres. Their pronounced gregarious habits and their 
voracity make them an easy prey; and as the flesh of 
most of them is well-known for its wholesome qualities 
and good flavour, many of them are the objects of most 
productive fisheries. 
The difference between the species of the genus is 
so slight that to divide it into subgenera, for which end 
several systems have been suggested, has hitherto proved 
almost impracticable. Still, the species compose several 
form-series, which, when we take into account the chan- 
ges of growth, appear to be stages of development, more 
or less advanced in different respects, and issuing from 
a starting-point that has probably been common to this 
genus and the following one. The first series contains 
one species in the Scandinavian fauna, Gadus poutassou, 
which is without pyloric appendages, and thus conies 
nearest the Hake ( Merlucius merluccius), which has only 
one appendage to the intestine. The Poutassou is also 
remarkable for the great length of the base of the first 
anal fin; and the history of development brings to light 
in the true Cods the general rule that the relative length 
of this fin decreases during the growth of the fish. In 
some of the species, however, the Coal fishes and Whitings 
for example, the length of the first anal fin is persist- 
ently at least more than half the distance between this 
fin and the tip of the snout; while in others the first 
anal fin invariably measures less than half this distance, 
this last group containing the true Cods. In two re- 
spects, which are indicated by different changes of growth 
of fair constancy, the Coalfishes and Whitings differ so 
greatly from each other that they may Avell be regarded 
as representatives of distinct groups in the system. The 
relative length of the snout increases with age, but that 
of the lower jaw decreases. In these respects the Coal- 
fishes occupy a lower rank in the scale of development 
than the Whitings. Again, the Coalfishes and their allies 
are distinguished from the true Cods by the greater 
length of the lower jaw (a relatively shorter snout) in 
the former; and the Haddock, which in this respect 
(with the relatively longest snout) stands highest in 
the generic development, thus claims a group for it- 
self in our fauna. 
These series of forms may be arranged according 
to the following characters: 
I: Length of the base of the first anal fin 
less than half the distance between this 
fin and the tip of the snout: 
A : Least depth of the tail at least about 
half (more than 49 %) of the length of 
the lower jaw.. Gadus ceglefinus. 
B: Least depth of the tail distinctly less 
than half (less than 46 /) of the length 
of the lower jaw: 
a: Least depth of the tail more than 
*/ 4 of the length of the pectoral fins 
or than 30 % of the length of the 
lower jaw: 
a: Length of the head more than 
v 4 of that of the body: 
aa: Least breadth of the inter- 
orbital space more than 28 % 
of the length of the head.. Gadus ogac. 
,3(3: Least breadth of the inter- 
orbital space less than 28-%, 
of the length of the head.. Gadus callarias. 
(3: Length of the head less than 
24 % of that of the body : 
aa: Length of the snout less 
than 2 / 3 of the postorbital 
length of the head; least 
depth of the tail more than 
41 % of the length of the 
lower jaw Gadus gracilis. 
(3(3: Length of the snout more 
than 68 % of the postorbital 
length of the head ; least 
depth of the tail less than 
40 % of the length of the 
lower jaw Gadus navaga. 
b: Least depth of the tail less than 
23 % of the length of the pectoral 
fins or than 29 % of the length of 
the lower jaw Gadus saida. 
II: Length of the base of the first anal fin 
more than half the distance between this 
fin and the tip of the snout: 
1 : Length of the base of the first dorsal 
fin more than 30 % of that of the base 
of the first anal fin, and the length of 
the base of the second dorsal fin more 
than 50 % of the latter: 
A: Upper jaw projecting beyond the 
lower jaw (length of the snout and 
the upper jaw-bone — distance be- 
tween tire tip of the snout and the 
a In Brown-Goode ( Fisheries and Fishery Industries of the United States, sect. I, pp. 202 and 223) we find instances given of the 
presence in North American rivers both of the Cod and the Toincod ; and according to Malm the Cod makes its way up the River Gotha as 
far as Hising Bridge, and is taken not so seldom off the Public Iron Stores of Gothenburg, where it keeps to the salt water at the bottom 
of the river. In Day (1. c., p. 271) the Earl of Ducie gives some personal observations on this point from Norway. He says that the 
Pollack occurs in Midlungen and, together with the Cod and Green Cod, in Sorejde Fjord — like Midlungen a salt-water tarn with fresh water 
at the surface — and that at least the Pollack ventured up into the fresh water to bite. 
Scandinavian Fishes. 
59 
