of the Fishery Board for Scotland. 207 



60 grammes) contain the highest percentage of fat in their muscles. 

 From a careful examination of all the tables, one is led, however, to 

 believe that practically until full maturation of the ovaries, there is an 

 increase in the weight of the fish, while after spawning the loss of weight 

 is greater than can be accounted for from the discharge of the ova. 



It is quite probable that the decrease in fat of the muscles is accom- 

 panied by an increase in water. It is unfortunate that, especially in the 

 case of the herring muscle, it is difiicult to obtain reliable figures for the 

 water percentage. There can be no doubt, however, that there is an 

 increase in the water percentage of the muscles in spent fish. As regards 

 the fat, there can be no doubt that there is a gradual loss of this import- 

 ant food material during the later stages of maturation, succeeded by a 

 serious loss after the spawning of the fish. This loss after spawning is 

 evidently a very rapid one as, although there must be a short period after 

 spawning when the spent fish contains practically the same amount of fat 

 as the full fish, it is rare that one observes this in analyses, and when one 

 does so it is possibly in some cases due to the fact that one is examining 

 a spent fish that is in the period of recuperation. 



When one remembers that the fat is the stored material which will bo 

 used up before the proteids of the muscles after the food intake becomes 

 insufiicient to cover the body requirements, one is led to suppose that, 

 for some time before full maturation of the ova, the fish either ceases to 

 feed or, what is more likely, takes an insufficient supply to prevent a 

 loss of the body fat. Tiie analyses which I have made support, therefore, 

 in the main, Heincke's conclusions as to the various stages in the 

 reproductive life of the herring {Twenty-fourth Annual Report of the 

 Fishery Board for Scotland, Part III., p. 102). If my supposition be 

 correct, then the fish is at its best, regarded as a sourse of nutritive 

 material, at a period somewhat short of full maturity of the genitalia. 



The herring is, however, very unlike the salmon in that there is 

 certainly no prolonged period during which the fish refrains from food. 

 There is only probably a short period in the reproductive life of the 

 herring comparable to that in the case of the salmon, and that is the 

 month, or probably two months, just preceding spawning, when the fish 

 has not only to obtain the necessary energismg material for work from 

 its own tissues, but has also to supply the growing ovaries or testes from 

 the same source. It is, however, after spawning that the muscles of the 

 fish lose the largest amount of their stored nutritive material, and it is 

 then that the most undoubted loss of weight occurs, over and above that 

 which can be accounted for by the complete discharge of the ovaries. 



There are two periods during which it would be most interesting to 

 know the changes which the nitrogenous constituents of the nmscles are 

 undergoing, namely, in the first place, during the later stages of matura- 

 tion and earlier period in the spent condition (a condition of starvation), 

 and secondly, in a later stage after spawning when recuperation is taking 

 place. 



I am at present investigating this subject of the alterations in the 

 chemical nature of the proteids of the herring's muscles during different 

 periods of reproductive activity. 



I would like to thank the various fishery officers for the care and 

 trouble taken in the packing and preservation of the fish. Without their 

 valuable assistance it would have been impossible to get the fish in pro- 

 per condition for chemical investigation. 



