of the Fishery Board for Scotland. 117 
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 defined. 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 when 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. 
Tue Fisues 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 luscws and minutus were got chiefly in 
the neighbourhood of Aberdeen. The G. esmarkit 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. 
Tuscus and nuinutus 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.8.E. of Cruden Scaurs, Aberdeenshire. Out of 38 
brassies, 36 were luscus and 2 minutus. Usually only an odd example 
of Juscus 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 fow minutus were 
caught on a haddock line near Aberdeen. 
In the following Table are set out the various points at which Juscus 
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°3, 11°4 and 16’6em. respectively. 
| TABLE. 
