from 1939, 54 samples, - 9, 000 herrings. The samples consisted of adults, first -time maturing, 

 spawning, and recently spent Murmansk herrings 2-7 years old. 



The material was taken principally in the southern part of the Barents Sea, and in the areas 

 frequented by concentrations of pre -spawning and spawning herring along the coast of northern 

 Norway. During the Greenland Expedition in 1947, 19 samples were taken, consisting of 1, 570 

 large adult herring, 8-14 years old. On the whole more than 16,000 herring have been investigated 

 during the whole period of investigation (1938, 1939, 1947). 



The histology of 133 ovaries, representative of the total mass of the investigated herrings, 

 has been studied. Also, 10 more ovaries of Norwegian herring from the Vesteralen region (the 

 material of Yu'. Yu. Marti) have been used in this study. 



In addition to the usual biological data (length, weight. Intensity of feeding, fatness, con- 

 dition, age), the composition of the blood has also been investigated. The ovaries from each her- 

 ring were weighed, and the index of maturity calculated as per cent of the weight of the fish. For 

 the description of each stage of maturity of the ovaries, macro- and microscopical data were given. 

 In addition, the geographical distribution of the herring in the sea was plotted, according to the 

 stage of maturity all the year round. 



The ovaries in stage I (juvenile) and II were sometimes preserved in whole . A small piece 

 was often cut out from the middle part of the ovary and preserved. For the determination of the 

 synchronous development of the ovocytes, pieces were cut out from the caudal, median and cranial 

 parts of the ovary. TTie ovaries were mostly preserved in Bouin's fluid with 4% of neutralized for- 

 malin, not later than half an hour after the fish had been caught. 



The ovaries wiiich had been preserved in formalin, were also kept in this fluid . Ovaries 

 preserved in the fluid of Bouln or Zenker, were transferred to 80% alcohol or glycerin after 24 hours. 



The preparations were transferred to xylol and ultimately imbedded in paraffin . Sometimes 

 ovaries of the later stages (IV, V) were imbedded in celloidln, because these objects were compar- 

 atively large, and the layers with ovocytes were of varying consistency. By the imbedding of ovaries 

 of stage rv and V into paraffin, the lumps of yolk were very often "stained" during the cutting. This 

 was never observed in the celloidln blocks . 



The sections were 6-7 mu thickness, sometimes in a longitudinal direction. The sections 

 were stained with Heidenhfin's haematoxylin . In a few cases, Mallory's stain was used. The 

 method of fixation and staining gave very satisfactory results. From the photomicrographs, one 

 may be convinced that the basic cell elements (the membranes, inclusions of nuclei and protoplasm, 

 and in some preparations the chromosomes also) are easily discerned. The study of the single 

 cytological elements does not come within our task. 



The photographs and photomicrographs were enlarged for a better comparison of the various 

 stages and to elucidate the different details in the structure of the ovaries . 



The ovocytes were measured by the aid of an ocular micrometer at a six-times enlargement. 

 The divisions of the ocular micrometer for the given enlargement of the Leitz microscope with the 

 tubes in were measured with an objective micrometer. The divisions of the ocular-micrometer 

 were measured for different enlargements. Because of the great variation in size of the ovocytes, 

 it was necessary to use different objectives . 



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