Ill] OF THE SIZE AND AGE OF HERRING 183 



accretion, each annual increment persisting without further change 

 after it is once laid down. This is what happens in a moUuscan 

 shell, which is secreted or deposited as mere dead substance or 

 "formed material"; but it is by no means the case in bone, and 

 we have httle reason to expect it bf the bony mesoblastic tissue of 

 a fish's scale. It is much more likely (though we do not know for 

 sure) that "osteoblasts" and "osteoclasts" continue (as in bone) to 

 play their part in the scale's growth and maintenance, and that 

 some sort of give and take goes on. In any case, it is a matter of 



Mean ajyparent length of one-year-old herring, as deduced by 

 scale-reading from herring of various ages or ''year-classes'^'' 



fact and observation that the rings alter in breadth as the fish goes 

 on growing f ; that the oldest or innermost rings grow steadily 

 narrower, while the outermost hardly change or even widen a little ; 

 that- the relative breadths of successive rings alter accordingly; 

 and it follows that when we try to trace the growth of a herring 

 through its lifetime from its scales when it is old, the result is more 

 or less misleading, and the values for the earher years are apt to 

 be much too small. The whole subject is very difficult, as we might 

 well expect it to be; and, I am only concerned to shew some 

 small part of its difficulty J. 



While careful observations on the rate of growth of the higher 

 animals are scanty, they shew so fax as they go that the general 

 features of the phenomenon are much the same. Whether the 

 animal be long-lived, as man or elephant, or short-lived hke horse § 



* From T. Emrys Watkin, The Drift Herring of the S.E. of Ireland, Rapports du 

 Conseil pour V Exploration de la Mer, lxxxiv, p. 85, 1933. 



t Cf. {int. al.) Rosa M. Lee, Methods of age and growth determination in fishes 

 by means of scales, Fishery Investigations, Dept. of Agr. and Fisheries, 1^20. 



X The copious literature of the subject is epitomised, so far, by Michael Graham, 

 in Fishery lyivestigations (2), xi, No. 3, 1928. 



§ There is a famous passage in Lucretius (v, 883) where he compares the course 

 of life, or rate of growth, in the horse and his boyish master: Principio circum 

 tribus actis impiger annis Floret equus, puer hautquaquam, etc. 



