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DEPARTMENT OF THE NAVAL SERVICE 



6 GEORGE V, A. 1916 



females associate with males which are younger than themselves. An examination 

 of the lines of growth upon the scales indicates that the former is the correct explana- 

 tion of the facts, the individuals of the two sexes being the same age. 



The morphology of the scales of the hake differs entirely from that of the scales 

 of the cod, haddock, etc., and bears some resemblance to that of the salmon scales 

 There is no succession of spiral, cyclic, and crescentic rings. The nucleus in the 

 centre of the scale is occasionally a short spiral, and in a few cases is a complete ring, 

 but usually it is a ring with a little break at the anterior end. Such rings, in the 

 form of a somewhat irregular ellipse continue, more or less uniformly spaced, until 

 the end of the ellipse reaches the end of the scale, leaving a perfectly clear strip 

 extending along the long axis of the scale from the centre to the anterior end. The 



Fig. 1. — Length-freqiiency curves for specimens of hake Nos. 53-352. The clear line repre- 

 sents all the feniales, the interrupted line all the males, the dotted line represents the 

 two sexes taken together. Dotted vertical lines represent means. 



rings then continue to the edge of the scale as curved lines along each side. In some 

 cases these lines, or rings, extend right to the extreme edge of the scale at each end, 

 but most scales have a narrow clear area along the posterior edge. 



The lines of growth, instead of being formed by a change in the nature of the 

 rings, are merely shady lines produced by a little irregularity in each ring along the 

 side of the scale and a roughened area across the posterior end. Where these lines 

 reach the clear area on the long axis they are marked by the ring nearer the centre 

 stopping abruptly at the clear space, while the next ring turns and runs along the 

 edge of this space for some distance towards the outside of the scale. It is this change 

 in the rings at the clear space which is considered to suggest the condition in the 

 salmon, where the rings alter in such a way as to form caps. These lines of growth 

 are sometimes very indistinct but are usually quite evident, though a little indefinite. 

 In several scales the distance of the innermost line from the centre would seem to 

 indicate that the first line is missing. 



That these lines represent a periodicity in growth there is no doubt, but whether 

 or not they are annual there is at present no means of determining, though this is 



