of the Fishery Board for ^Gotland. 



135 



The teeth of the outer series in the upper jaw are a little larger than 

 the inner ones. 



The snout is almost equal to the length of the diameter of the eye. 

 [This character is preferably expressed as follows : — The diameter of the 

 eye is equal to or exceeds the length of the snout.] 



The eye is very large, being a little less than one-third of the length of 

 the head. 



The barbel is slender, being about half as long as the eye. 



The fin-formulae were— 1 D, 15- 16 ; 2D, 23-25 ; 3 D, 22-25 ; 1 A, 

 27-29; 2 A, 23-25. 



In the " Scandinavian Fishes " the fin-formulae are given as follows : — 

 1 D, 14-16 ; 2 D, 22-26 ; 3 D, 22-27 ; 1 A, 26-30 ; 2 A, 24-38. 

 Pect., 19. Ventr., 6. Vertebrae, 52. 



Attention is called in the latter work to the lateral line which is u dark 

 (though not very distinct) and anteriorly slightiy curved." 



The numbers of fin-rays and vertebrae found in the esmarkii examined 

 for the purpose of this research are set out in Table III., p. 145. 



Gunther drew attention to the cysts that are found in the eye of 

 esmarkii. They are arranged in the iris, may be few in number, or they 

 may occupy almost the whole of the iris, in this way appearing as a ring 

 of white balls. These cysts occur in minutus also. 



In 1893 Professor M'Intosh described a "peculiar Poor Cod" which 

 is, he informs me, a Gadus esmarkii. Professor M'Intosh has kindly 

 permitted me to have a drawing made of this specimen, and it is 

 reproduced in pi. ix. 



Since then Dr. Fulton has obtained it in large numbers. Schmidt has 

 described in detail the post-larval and young stages of G. esmarkii up to 

 a length of 5"4cm. He remarks that in an example of 19mm. the eyes 

 are but relatively small, their diameter being of the same size or but little 

 larger than the distance from their anterior margin to the end of the 

 snout. 



A Specific Description. 



For the purpose of determining the specific description a large number 

 of measurements was made on specimens of each species. These show 

 that external measurements made on a single fish may be of little value 

 from the point of view of specific diagnosis, since the variation of each 

 character is large, and, so far as is apparent, independent of, or at least 

 not necessarily correlated with, any other contiguous character. The 

 amount of variation which may occur in the characters, while the general 

 specific identity is retained, is large. Specific identity means identity of 

 function. The specific characters mean a difference in the life and habits 

 of the animal which we may not be able at present to estimate. The 

 correlation between the specific characters and the life of the fish is a 

 field hitherto practically unexplored. Thus there are perplexing simi- 

 larities and differences between fishes. The former mean that the fishes 

 perform similar functions, but at the same time in certain other functions 

 they occupy different spheres in the economy of the sea. 



In working out the specific characters it is well to consider the points 

 in which the species agree, in order that these may form part of the 

 generic or sub-generic description. The object of the specific description 

 is to enable an observer to diagnose a single fish, and for that purpose a 

 chart is required. 



The Genus may be divided into certain sub-genera. The species may 

 be arranged into two or more groups, each characterised by some common 

 character. The species in each sub-genus may then be distinguished 



