Figure 2. Ovary of a Murmansk herring, Jan. 17, 1939. Northern edge of the Murmansk 

 coast -bank. Length of fish 225 mm., stage II-III. The transversal lamellae 

 of eggs, and the cavity of the ovary are visible. The youngest ovocytes are 

 found in the periphery of the ovigerous lamella . 



The phase with follicle tissue in one single layer. The pellicle (membrane) surrounding 

 the egg cell is still slender, without any structure. The nuclei in the follicle epithelium lie at a 

 short distance from each other, forming one single layer. The cytoplasm is granular. Numerous 

 nucleoli are distributed at the periphery. The chromosomes are as before. The diameter of the 

 ovocytes varies from 86.87 mu to 138.7 mu, average 103.66 mu. The diameter of the nucleus, 

 56.21-76.85 mu, average 65.70 mu. During the further growth the ovocytes pass over to next 

 phase. This transition takes place by degrees. 



The phase with formation of yolk. In this phase, the ovocytes form a follicle in two layers. 

 In the inner layer the nuclei have an extended, oval shape, comparatively larger than the slim, 

 compressed nuclei in the outer layer. 



TTie diameter of the ovocytes varies from 240 to 352 mu, average 292.8 mu, the nucleus, 

 96-128 mu, average 113.6 mu. 



In the transitional [Aase the pellicle of the ovocyte is structureless. During the growth of 

 the ovocyte, however, the pellicle gets a fine, radiate structure, i.e., the "Zona radiata" is form- 

 ed. (In his monograph on the cell Vilson (108) remarks that in fish a pronounced zona radiata is 

 formed on the egg itself). The early formation of a zone with radiate structure (zona radiata) is 

 also found in Alosa fallax (Loewe). (In other species of fish, plaice (Frantz), perch (Meien), vobla 

 (Melen), the zona radiata is not yet formed in this phase). 



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