3l6 BULLETIN OF THE BUREAU OF FISHERIES. 



If the ratio of the number of radii present to the number expected represents rela- 

 tive activity, a speculation may be ventured that activity decreases the third year. (See 

 table 5.) It is at least possible that the activity, if variable at all, drops at first spawn- 

 ing, and decreases with age. This sudden decrease, followed by a continued decrease 

 points to the third year as maturity, or the time of first spawning. If this is true, 

 market fish ought to agree in size with fish of this age. 



(4) The oldest fish caught was 8 years old, and at this age the annuli were so close 

 together as to make their enumeration very difficult. It is likely that they seldom 

 exceed this age, although fish of much greater size and probably greater age are reported 

 from more northern waters." 



(5) It may be inferred from observations of the scales that winter habits do not 



differ greatly from those of summer, the annuli alone not being sufficiently pronounced 



to warrant such a belief. At any rate, very little evidence has been gathered from 



scales bearing on this point. 



CONCLUSIONS. 



AGE DETERMINATION. 



Age may be determined in two ways: (i) By counting the annuli, the count 

 being facilitated by (a) polarized light, (6) picrocarmine stain, (c) beginnings of radii; 

 (2) by year groups in length and weight. 



RADII. 



The following observations support the theory that radii are hinges permitting the 

 scale to bend: (i) Scales on inflexible parts of the body have no radii, while their num- 

 ber when present is proportionate to the degree of flexibility. (2) In thick scales the 

 radii are seen to close when the scale is flattened. (3) In broad scales the radii are more 

 numerous than in narrow scales. (4) Very young (uncalcified) scales have no radii; 

 in older scales they appear to begin at some distance from the focus. (5) In cross 

 section they appear as ridges of calcified matter on the flexible uncalcified substratum ; 

 when these ridges approach each other the scale is so bent as to make it more nearly 

 flat. (6) Scales whose anterior angles are prolonged and acute have parallel radii; 

 those with rounded anterior peripheries have divergent radii. (7) Radii stain as uncal- 

 cified parts with picrocannine, the stained uncalcified layer below being visible through 

 the radii fissures. (8) Those radii which do not begin at a point near the focus usually 

 have their beginning at an annulus which is explained by the tendency of a lamina to 

 crease without the support of the next superior lamina. (9) The radii on the several 

 laminae are in straight line one with another. This is explained by the support of the 

 inflexible parts between the radii, i. e., the newly formed laminae will bend in lines coin- 

 cident with those of the next superior lamina, (lo) No previous theory explains them. 



CIRCULI. 



(i) The number, distance apart, and mode of growth of the circuli afiford no evi- 

 dence as to the cause or periodicity of the annuli; (2) they are of uniform distance 

 apart, regardless of the rate of growth, hence they do not represent definite periods of 

 time; (3) their function is probably that of anchoring the scale in the pocket. 



*> Gill* Theodore; Natural history of the weakfish. Transactions of tlie American Fisheries Society, p. 269-276. Washing, 

 ton, 1910. 



