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Part III. — 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. caUarias, 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, callarias, 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, i.e., 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 t o render 

 a character, even an important one, doubtful. For example, a G. esmarkii 

 may be found in which the mouth is fixed wide open, the hyoid and 

 b^anchiostegal 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. minutus 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, pi. viii. ; Minutus, fig. 1, ib.\ Esmarkii, pi. ix. 



They are all three small fishes. The laigest size of luscus and minutus 

 appears to be 17 inches (42cm.), and Fulton gives 10 inches as the length 

 of the largest esmarkii recorded so far. 



Luscus and minutus are deep fishes. While luscus 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 app'eared to be that in the deeper fish the ovaries were 

 rather larger than in the other lot. In a deep fish variations in depth are 

 readily noticed. Where the character is large the variations are compara- 

 tively large. Esmarkii is a more slender fish than the preceding. 



