THE STRUCTURE AND GROWTH OF THE SCALES OF THE 

 SQUETEAGUE AND THE PIGFISH AS INDICATIVE OF LIFE 

 HISTORY. 



By HARBEN F. TAYLOR," 

 Scientific Assistant, U. S. Bureau of Fisheries. 



Contribution from the United States Fisheries Biological Station, Beaufort, N. C. 



INTRODUCTION. 



Since the invention of the microscope, fish scales have been the subject of numerous 

 investigations and heated controversies '' relating almost wholly to structure, phylo- 

 genetic relations, and taxonomic value. It was not until 1898 that scales were thought 

 to bear evidences of the age and life history of the fish, when Hoffbauer (1898, 1900) 

 observed on the scales of carp concentric rings which he supposed to be growth rings. 

 The discovery of these rings and their supposed relation to age and life history has 

 actuated a renewal of investigations in England, Germany, Scotland, Norway, and other 

 countries. 



These concentric rings (or annuli, as they are called in this paper) are supposed 

 to be produced by varying rapidities of growth. This theory has been applied minutely 

 to investigations of Atlantic salmon and English brook trout and, to some extent, to cod, 

 flounder, sole, eel, halibut, smelt, herring, mackerel, and other fishes, and by it an elabo- 

 rate life history of the salmon has been worked out. 



The theory has been objected to, especially by Tims (1906) and Brown (1903). 

 The uncertainty existing as to regeneration and constancy of growth has given rise to 

 grave doubts as to the reliability of these indications of age and life history. The 

 fact stands out, as Masterman (1913a) shows, that these indications of age have never 

 been satisfactorily tested; the relation of the annuli to growth has been a supposition, 

 and investigations have been limited to a small number of species. 



In America Cockerell, only, has worked on the taxonomy of scales, Nickerson, 

 Ryder and Cockerell on their phylogenetic relations, and it is only recently that work 

 on life history has been begun by Gilbert and McMurrich on the Pacific coast salmon, 

 and Thompson on the hahbut. 



It is the purpose of this paper to embody the results of investigations directed toward 

 explaining the various scale characters employed in the determination of life history, 

 their origin, constancy, bearing on life history, the various methods of detecting them, 



« The writer acknowledges with thanks the assistance in writing this paper and valuable suggestions as to illustrations by 

 Dr. J. J. Wolfe. 



*> For an excellent review of the literature of fish scales, see Thomson (igo6). 



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