136 Part ITI.—Twenty-fourth Annual Report 
from one another. Each species might appear in several sub-genera. 
For example, the members of the cod family discussed in the previous 
paper and in this, include G. callarias, G. virens, G. pollachius, 
G. luscus, G. minutus, and G. esmarkii. Now, these may be divided 
into two groups, as follows:—(a) Group of large fish, callartas, virens, 
and pollachius; (b) group of small fish. Thus, if the fish is over 17 
inches in length it will probably belong to the first group, if less than 
that it may belong to either group. 
Nothing should appear in a specific description except what can be 
readily gauged without the aid of any accurate measurements. A 
measurement shown as a percentage of the length is a poor guide except 
when its fullest range of variation is taken, for its value. The average is 
of no value by itself, z.¢., as a specific character. It may be used to show 
broad relationships. 
Even in the case where two species are so distinct that a glance is 
sufficient to separate them, still it is often very difficult to get readily 
gauged characters sufficient to describe the species. The attempt is made 
to describe a solid by means of a few characters, which are usually mere 
distances. 
The Diagnosis of a Species. 
The simplest mode of diagnosing a species is by means of a key of the 
genus. Accompanying the key there should be a particular description of 
the general appearance of each species. The key should be full, so that 
the species may be determined by different routes. There is hardly a 
single character which can be absolutely depended on. The specimen 
which it is desired to diagnose may be affected in such a way as to render 
a character, even an important one, doubtful. For example, a G. esmarkit 
may be found in which the mouth is fixed wide open, the hyoid and 
branchivstegal apparatus having become rigid. In such a specimen it 
could not be determined whether the lower jaw projected in front of the 
upper or not, and in this way a very valuable character becomes unavail- 
able. In another case a G. ménutus has been observed in which the 
lower jaw projected out in line with the upper jaw, if it did not actually 
pass it slightly. The sum or resultant of the characters has therefore to 
be relied upon for the sure diagnosis. 
General Appearance of the Three Species. 
Luscus, fig. 2, pl. vili.; Minutus, fig. 1, 2b.; Hsmarki, pl. ix. 
They are all three small fishes. The laigest size of Juscus and minutus 
appears to be 17 inches (42cm.), and Fulton gives 10 inches as the length 
of the largest esmarkit recorded so far. 
Luscus and minutus are deep fishes. While dwscus is the deeper of the 
two, still considerable variation exists in minutus in this character. In 
one catch of minutus obtained in February it was possible to divide the 
fishes into two groups, in one of which the members were distinctly 
deeper than those in the other group. The deep group consisted of 15 
females measuring from 21cm. to 24cm., while the narrower specimens 
numbered 42. Of the latter, 7 were males measuring from 17‘5cm. 
to 22cm., and the remainder, 35 females, measured from 20cm. to 25cm. 
in length. All the fishes had well-developed reproductive organs, and the 
only difference appeared to be that in the deeper fish the ovaries were 
rather larger than in the other lot. Ina deep fish variations in depth are 
readily noticed. Where the character is large the variations are compara- 
tively large. Hsmarkit is a more slender fish than the preceding. 
