species of fish, in this case the Atlantic herring, are not caused by a spawning in distinct periods, 

 but occur because the sexual products do not mature at the same time in the individual populations 

 of herring. 





Figure 1. Ovary of Murmansk herring, a: 21 Jan. , 1939, NW edge of the Murmansk Bank, 

 length of fish 248 mm., weight 126 gm., age frf, stage III, x 100. b: 1 March 

 1937, western part of the Murmansk Bank, stage IV, x79. B: April 4, 1939, 

 Ringvassi^y, fish length 239 mm., weight 89 gm., age Sf, stage VI. 



In the sections are seen: i) numerouo empty follicles, 2) a complex of ovo- 

 cytes in stage II, 3) a ripe ovocyte, which has not been spawned, x 100. 



From a study of our preparations Meien (49) came to the conclusion that the Murmansk her- 

 ring and the Caspian genus Alosa (very nearly related systematically) resembled each other very 

 much in the morphology of the ovocytes, but had different types of spawning. In Clupea harengus 

 there is a total sfiawning; in Alosa, a partial one. The difference is ascribed by Meien to the 

 different ecological conditions of the spawning. 



205 



