of the Fishery Board for Scotland. 



li- 



on specimens of each species, and also to determine to what extent the 

 dimensions vary in the same species. The number of fin-rays in the 

 unpaired fins and the number of vertebrae formed the basis of comparison. 

 In the selection of the measurements a wide choice exists. It is 

 important to have measurements and characters in which the different 

 forms agree accurately denned. Such characters should not be included 

 in the specific description ; they belong to the sub-genus. The intro- 

 duction into a specific description of the relation between the sizes of 

 two characters, both of which do not lend themselves to accurate defini- 

 tion, should be avoided. 



There are certain characters selected, to which one is guided by the 

 general appearance of the fish. A glance at the forms wheu compared 

 side by side will often indicate possible specific differences. These points 

 of difference sometimes vanish when a number of fishes have been 

 examined ; they may be found to be peculiar, individual, and not specific. 

 Many and varied characters may be from time to time adopted, to be 

 dropped again on account of the difficulty of suitably measuring the 

 quantities. 



Most of the measurements which were made will be discussed in 

 detail. The values of such characters for specific distinction is in that 

 way determined. 



All the measurements have been expressed in terms of the length of 

 the fish. 



The Fishes Examined. 



All the fishes which have been studied for the purpose of this 

 research were obtained in the North Sea, with the exception of 4 speci- 

 mens of Gadus minutus which were kindly sent from Plymouth* by Dr. 

 H. M. Kyle. The specimens of luscus and minutus were got chiefly in 

 the neighbourhood of Aberdeen. The G. esmarkii were obtained during 

 Dr. Fulton's trawling investigations in the North Sea. Some were 

 obtained off Aberdeen and in the Moray Firth, others were captured in 

 the vicinity of the Shetland Islands. The esmarkii were got in the 

 small-meshed cod-end with which the ordinary trawl was covered. The 

 luscus and minutus were taken in the ordinary trawl. 



Luscus and minutus are often confused, and are known collectively 

 under the names "Brassies," "Miller's Thooms," " Skelchies," "Davies," 

 etc. They were obtained on or near hard ground within a radius of 25 

 miles from Aberdeen. Luscus was obtained on one occasion in quantity 

 at a point 6 miles E.S.E. of Cruden Scaurs, Aberdeenshire. Out of 38 

 brassies, 36 were luscus and 2 minutus. Usually only an odd example 

 of luscus was obtained among frequent little lots of minutus. Luscus and 

 minutus are frequently got on the haddock lines, but only in small 

 numbers. On 11th June, 1906, one luscus, and four minutus were 

 caught on a haddock line near Aberdeen. 



In the following Table are set out the various points at which luscus 

 and minutus appeared among the fishes taken in the trawl of the s.s. 

 "Fifeness," Aberdeen, during the spring of 1905. 



* These were 4 females measuring 11, 11 % 11'4 and 16 '6cm. respectively. 



[Table. 



