of the Fishery Board for Scotland. 



127 



are very transparent. Secondly, 1 have not found that the external layers 

 in the otoliths of plaice killed between November and April were dark 

 opaque layers, but, on the contrary, in otoliths at this period the peri- 

 pheral layers were of the more transparent kind. Thirdly, the conclusions 

 of Reibisch seem to me to be in contradiction to the facts concerning the 

 first or central region of the otolith, and Reibisch excludes the deposit 

 of the first year from consideration on the ground that during this year 

 the young fish are exposed to very varying conditions of whose influence 

 on the organism we know next to nothing. I fail to see the force of this 

 remark ; it seems to me we have as much ground for reasoning about the 

 first year as about any other. Now, though the eggs are produced early in 

 the year, when the water is cold, the young plaice do not complete their 

 metamorphosis until May or June. The first specimens which I received 

 this year from Dr. Fulton were caught at four to eight fathoms on May 10. 

 In these the only part of the otolith formed was the central kernel, and 

 apparently not the whole of that. Therefore, it is evident that the opaque 

 portion of the first year's zone, outside the nucleus, is formed in summer, not 

 in winter, in warm water, not in cold ; and the condition of the otolith 

 with only the first year's zone, from fish caught in February or March, 

 equally proves that the more transparent zone is formed in winter, not 

 in summer. 



This interpretation might seriously affect the conclusions of Reibisch 

 concerning the age of the fish which he examined, as it seems probable 

 that he has interpreted, in some cases, as the commencement of the fourth 

 year's deposit, a zone which in reality represents a whole year of age. 

 Thus fish which he has taken to be three years old might in reality have 

 lived four years. 



Jenkins investigated the determination of age from the otoliths in 

 herring and other Clupeidse. He finds that in the herring there are 

 layers in the otolith as in the plaice, but with some differences. The 

 central nucleus is always transparent, not opaque ; the opaque zones are 

 much broader in proportion than in the plaice, and separated by very 

 narrow transparent zones, which, according to Jenkins, are formed at the 

 beginning of the new year. It would seem more probable that, as in the 

 plaice, these form the end of the year's deposit. Jenkins' paper is illus- 

 trated by photographs of the object, in which the different zones are not 

 always very distinct. The structure could, I believe, have been shown 

 more satisfactorily by drawings. Jenkins finds that the herring of the 

 Western Baltic have the following lengths at successive years of age : — 



1st year, ..... 11-3-12'lcm. 



2nd ,, ..... 15-6-16 - 4cm. 



3rd „ 19-0-19-8cm. 



4th „ 21-7-22-5cm. 



5th „ 23-7-24-5cm. 



Jenkins rejects the conclusion held by nearly all naturalists who have 

 investigated the herring, that two season-races can be distinguished, on 

 the ground that ripe or nearly ripe or spent herrings can be found in 

 the Western Baltic at all times of the year. 



He has misunderstood a statement which he quotes from myself, that 

 two spawning periods have undoubtedly been observed in the same 

 neighbourhood, stating that it is in contradiction to Heincke's assertion 

 that herring spawn is never found twice in the year on the same spot. 

 There is really no contradiction. Anyone acquainted with the subject 

 knows that spring or winter spawning herring and summer or autumn 

 spawning herring are captured by fishermen in large numbers in the same 



