116 Part IIT.— Twenty-fourth Annual Report 
V.—ON THE SPECIFIC CHARACTERS OF GADUS LUSCUS, 
GADUS MINUTUS, and GADUS ESMARKII. 
By H. Cuartes Wititamson, M.A., D. Sc., Marine Laboratory, 
Aberdeen. 
(Plates VIIT.-X.) 
CONTENTS. 
PAGE. 
Introduction, - = : = d E 116 
List of Body- amencione, - - - - - 5 119 
List of Enumeration- Char acters, - : : < : 121 
Discussion of the Averages, - - > = - 12] 
The Numbers of Fin-rays, - - = - - = 124 
The Numbers of Ver tebrae, - - - - - 129 
The Reproduction of the Three Species, - - - - 130 
The Skulls of the Three Species, - - 5 - - 131 
A Discussion of the Species, - - - - : 133 
A Specific Description, - - - - : - 135 
The Diagnosis of a Species, - . - - - 136 
General Appear ance of the ‘I'hree Species, - - - 136 
Key, - ; - - - 138 
Literature, - - - - - - - : 139 
List of Tables, - - - - - 141 
Tables, = . - - - - - 142 158 
INTRODUCTION. 
The present research is a continuation of the paper contributed to the 
Twentieth Annual Report of the Fishery Board for Scotland, Part II1., 
entitled, ‘“ A comparison between the cod (Gadus callarias), the saithe 
(Gadus virens), and the lythe (Gadus pollachius) in respect to certain 
external and osteological characters.” In that paper a beginning was 
made with the review of the species of the genus Gadus. In several 
instances the accepted specific descriptions are unsatisfactory ; so much so 
is this the case that difficulty is experienced in separating certain species. 
A certain amount of confusion has existed in the diagnosis of G. luscus 
and G. minutus ; and the third species, G. esmarkiz, which has, through 
Dr. Fulton’s trawling experiments, been shown to be common in Scottish 
waters, might in its smaller stages be mistaken for a young minutus. The 
three species under review are the three smallest species of the genus; 
in the former paper the three largest members were dealt with. A 
systematic study of the three forms has become necessary in order to 
definitely fix the specific characters, It is very seldom that a single 
member of a species will exhibit all the distinguishing characters well. 
it has thus been necessary to examine a considerable number of specimens 
of each species. The main purpose is to arrive at an accurate and suitable 
specific description, and with this end in view, both the characters in 
which they agree, as well as those wherein they differ, must be studied. 
A minute comparison is therefore instituted between the three forms, and 
by the method which was adopted in the previous research, The method 
has been to make a number of measurements on the body of the fish, in 
order to determine the comparative magnitude of corresponding distances 
