of the Fishery Board for Scotland. 



55 



stated. Owing to the great variety of conditions it is necessary to take 

 into consideration the time of year when discussing the reproductive 

 organs and their development. 



The stage of a reproductive organ is indicated in some measure by its 

 colour. A developing ovary is pink. When the yolked eggs become 

 large the ovary becomes white in colour, with the blood-vessels prominently 

 shown. Sometimes the infiltration of oil from the abdominal organs into 

 the ovary after the death of the fish causes the white eggs to become 

 translucent, and in that way the ovary may a,ppear to be further advanced 

 than it actually is. When quite ripe the ovary loses its white colour and 

 becomes translucent. 



The testis when small and developing is pink in colour. When ripe it 

 is white and contains the white pasty milt. 



Up to a certain period of the life of the fish the ovary and testis only 

 grow to a preparatory condition and then rest. Six months before the 

 herring will spawn it will be* found to have laid up a large store of fat in 

 the abdomen. This quantity of fat is not a provision for the growth of 

 the body. The immature herrings, 13 to 21 cm. in length, in December 

 had large quantities of abdominal fat, but they had nevertheless been 

 feeding largely, for their stomachs were full of copepods. The presence of 

 the fat indicates that the food supply has been more abundant, even in the 

 winter season, than was necessary for the growth of the fish. The fish, 

 therefore, has stored up the excess of nourishment in the form of rolls of 

 fat, which are a reserve for the formation of the roe and milt.* When in 

 this condition, that is, where a very small reproductive organ is accom- 

 panied by a large quantity of abdominal fat, the herring is known as a 

 " matje." Spawning, then, appears to take place at a period in the life of 

 the fish when it is able to assimilate more food than it requires for growth. 



Fulton suggests that the fat^found in the abdominal cavity of the 

 herrings caught in autumn is probably used up not only in connection 

 with the development of the reproductive organs, but also for the produc- 

 tion of energy in tiding over the winter, when growth and even the power 

 of digestion is to a large extent in abeyance. 



The presence of much abdominal fat in an immature herring in winter 

 or summer is a probable indication of impending maturity, viz., that the 

 reproductive organs are about to start ripening in order to spawn in six 

 months' time. 



In February the immature herrings which will spawn during the 

 coming summer may thus be detected. In the following Table are set 

 out the conditions as to the quantity of abdominal fat observed in those 

 immature fishes in which the character was noted. The immature 

 developing herrings are omitted. The amount of fat is shown in four 

 quantities — none, some, much, and very much. 



* See also p. 64. 



[Table. 



