288 BULLETIN OF THE BUREAU OF FISHERIES 



and numerous other statistical relations the age data obtained from the scales give a 

 rational and consistent result throughout." The more recent literature, however, 

 shows a tendency that views with some skepticism certain phases of the scale theory. 

 One or more of the assumptions (p. 278) of the scale method, wliich were taken for 

 granted by most of the investigators of some years ago, are now being subjected 

 to a more critical examination. Further, whereas previously an assumption found 

 vaUd for one species of fish was accepted in many cases without investigation as 

 valid for another, now the tendency exists to consider each species on its own merits. 

 These present tendencies justify a reconsideration of the whole scale theory, but 

 espeoially of the assumption that annuli are age marks — the keystone of the theory. 

 In this section, then, an attempt has been made to review all the criticisms that have 

 been directed against the age hypothesis and the nature and extent of all the 

 evidences, direct and indirect, that support or contradict the hypothesis. 



CRITICISMS 



Brown (1904) comes to the conclusion that the concentric rings (circuli) on 

 gadoid scales do not represent annual increments because (1)' scales obtained from 

 different parts of the body show 90, 60, or 30 rings, according to the part selected 

 and (2) because the scales are shed immediately after spawning. Tims (1906) con- 

 curred with Brown and found further (3) that he could not detect a regular alter- 

 nation of narrow and broad zones on the scales of Gadidse after the first annulus 

 (a photograph of a scale of a cod 2J^ feet long showed no year rings), and (4) that in 

 clupeoid scales the annuli varied in number in scales removed from the same situation 

 from the same fish. This same variation in the number of annuli was found in the 

 marine herring by Buchanan-Wollaston (1924) and Hodgson (1925), in the eel by 

 Gem?oe (1908), in the Atlantic salmon (rarely) by Calderwood (1911), and in the 

 lake herring (rarely) by the writer (p. 271). In the haddock, Thompson (1923) 

 found that all scales of a fish show the same number of annuli, "with the exception 

 of those, which, l^'ing on the head and the bases of the fuis, were as many as two years 

 short and are evidently much later in being developed [p. 16]." Both Buchanan- 

 Wollaston and Hodgson discovered that certain symmetrical scales taken from the 

 region between the dorsal fin and the tail, above the lateral hne, often were found to 

 show a less number of rings than the scales from the anterior part of the body. Either 

 the former scales cease to develop after three or four years or the latter become 

 "ringy." Hodgson (192,5) waites, "The generally accepted theory that all the scales 

 of a fish exhibit the same number of rings is erroneous. This, of course, does not mean 

 that in a complete suit of scales a widely different number of rings can be found, 

 but, rather, that in certain areas, on larger fish, the number of rings may be less than 

 the modal number for that particular herring [p. 3]." The scales of Gemzoe's 65 centi- 

 meter eel showed from 1 to 6 annual rings, the number vaiying with the areas on the 

 body. 



Gemzoe (1908) claimed (5) that the scales of the eel first appear after the second 

 year of life, while Schneider (1909) asserted that the scales of the eel {Unguilla 

 vulgaris Flem.) form in either the third, fourth (usually), or fifth summer. "Als 



• The criticisms are numbered consecutively. 



