of the Fishery Board for Scotland. 



103 



A callarias, 69 cm. in length, was caught near Aberdeen. It had been 

 mutilated All its fins had been trimmed. The pectoral and ventral fins 

 had been cut off short, movable stumps only being left. All the dorsal 

 and anal fins and the tail fin had been partly cut away. One eye had 

 been destroyed. All the fins had healed and the fish was well nourished. 

 The stomach contained crabs. 



The tables given above are useful in showing characters which are 

 hidden when the fish is examined ; but they are mainly of service in 

 estimating the exact value of the characters which have otherwise attracted 

 attention. In a group of fishes, as that of the genus Gadus, it is not 

 possible to separate the different members by a simple scheme, because 

 the character which may be of value for separating two species may be 

 quite neutral in the other eleven members of the genus. It is therefore 

 necessary to take the characters of the fish seriatim, making each one a 

 basis for classification. It has usually been thought necessary to sub- 

 divide the genus by the test of a single character — for example, by the 

 question of whether the upper or the lower jaw forms the more anterior 

 point of the fish when the mouth is closed. Then in each sub-group the 

 individual members were separated by other characters. Theoretically 

 this is a convenient arrangement, but in practice it is of little value in 

 some cases. For the first selected character may not be readily 

 recognisable in some specimens, and in that case the diagnosis may not be 

 obtained. 



A character which is very noticeable in examining different members 

 of the genus Gadus is the varying size of the eye. The size of the eye 

 has been compared by previous authors to the length of the snout and to 

 the length of the barbel. The species may then be grouped according as 

 the eye is less than, equal to, or greater than the snout. An examination 

 of the tables given above will reveal how the species will range them- 

 selves under this classification. But while in one species the result will 

 be at once apparent, in another the relationship may be doubtful. That 

 is due to the range of variation in each character. For example, in 

 callarias the diameter of the eye equals 3 , 3-4 , 6, while the length of the 

 snout is 7'5-8*9. In this fish the eye is always less than the snout. 

 But in merlangus the relationship is more obscure, the eye measuring 

 4 , 9-8 , l, while the snout equals 6-9. In such a case it is necessary to 

 refer to the measurements* of each fish, and find out the relationship of 

 the eye and snout in each individual specimen. The result of that 

 enquiry is to show that in merlangus the eye was, in the majority of 

 cases, less than the snout, but it may be equal with it, or it may exceed 

 the snout by a very little. In those fishes in which the lower jaw 

 projects in front of the upper the tables do not show the size of the snout. 

 They give the position of the orbit with reference to the tip of the 

 mandible. The distance between the mandible and the premaxilla must 

 be subtracted from the orbit distance in order to get the length of the 

 snout. In all cases the corroboration of the character must be made on the 

 fishes. This character, the relation of the snout and eye, is a good one 

 for certain fishes, and of less value for others. There is probably hardly 

 a single character or comparison between two characters but may be of 

 more or less value for diagnosis. 



There is a certain amount of evidence to indicate a change in the size 

 of certain characters with an increase in the length of the fish. Thus the 

 eye was found to be larger in small seglefinus, virens, pollachius, and to a 

 certain extent merlangus, than in big fishes of these species. In the com- 

 parison in length between the pectoral fin and the first dorsal fin of 

 # The measurements made on the fish a»*e not published here. 



