SEA-FISHERIES LABORATORY. 115 



estimated by the analyses, and one is not compelled to assume 

 that the dry fat-free, ash-free, residue is proteid having a 

 percentage of nitrogen = 16. As the analyses show this per- 

 centage varies between about 15.5 and 13.7%. The work 

 done by Milroy* indicates that there are interchanges of 

 substance between the flesh of the herring and the reproductive 

 organs during the period of maturation of ova and spermatozoa. 

 The proteids present in these tissues are certainly markedly 

 different in composition, and it is also certain that, in each case, 

 there are differences according to the stage of development of 

 the gonads. What these differences are and what they mean 

 have still to be made out. Neither must one assume that the 

 " oil " in the flesh is always the same chemically, and here 

 again precise investigation of seasonal changes would be very 

 interesting. 



On the whole these seasonal changes in the proportion of 

 oil, water, and proteid, are repeated year after year in much the 

 same way as Fig. 1 indicates. But there are quite marked 

 (though minor) differences between one year and another, and 

 Fig. 2 is meant to show this. The percentages of oil alone are 



Pig. ■> 



* " Food value of the Herring," 2<Wt Ann. R< pi. Fishy. Bd. for Scotland, 

 Pt. Ill, pp. 83— 107, L906. Ibid. 25th Kept., pp. l«)7 208,1908. "Chances 

 in the chemical composition of the Herring during the Reproductive period," 



Biochemical Journal, Vol. Ill, pp. .'507 :!'.)<>. 



