Macroscopic criteria (cont'd) 



16. Degree of extrusion of the ripe eggs. 



17. Presence of single white, opaque, and degenerating eggs . 



18. Presence of single ripe eggs which have not been spawned. 



Microscopical criteria: 



1. Visibility of single eggs with a magnifying glass or microscope. 



2. Presence of a certain complex of ovocytes in various phases. 



3. The degree to which the single egg cells are filled with yolk. 



4. Characteristic features in the egg pellicle (microscopical). 



5 . Presence of empty follicles . 



The majority of the criteria mentioned above are thus macroscopical . 



In 1909, Frantz (84) described the maturity stages of the plaice from a microscopic point 

 of view. From that time, the histological method was steadily used in similar investigations, 

 especially by the Soviet investigators (Gerbil'skiy, Meien, Gryazeva and others) in competition 

 with the macroscopical method. 



There is no need for giving a thorough characterization of the maturity scales. Many of 

 them are too old, and those which are still of any value will be treated critically in the present 

 paper. 



All the known scales of maturity are given in Table 8, with information on the criteria on 

 which they are founded . 



The first scales were merely based on the visual description of the gonads (color, the con- 

 sistency of the gonads, visibility of the ovocytes with the naked eye, and so on), and the evaluation 

 is accordingly very subjective. 



Several investigators found the scales of maturity at hand insufficient, and tried to adapt 

 them for other species of fish. The scale of Heincke was supplemented by Maier (1906). 



In turn Lea (1910) improved the Heincke -Maier scale, and at last Vukotich in 1915 changed 

 and adapted the scale for the Caspian herring. These authors did not add anything new to the 

 scheme of Heincke . 



Maier supplemented the scale of Heincke and adapted it to the plaice, assuming that the new 

 scale might be used for all kinds of fish. In our opinion it was a mistake of Maier to extend one 

 scheme to be valid for "all fishes", as it is even impossible to work out a satisfactory scale for 

 one family, genus, or species of fish. 



"The egg of each species has its own specific character of development" (Vilson 109). In 

 the development of the species and subspjecies, the maturing of the gonads as a whole proceeds in 

 different ways. This is conditioned by the great biological differences within the species itself, 

 and still more within large taxonomic groups. This circumstance is evidently explained by the 

 presence in one species only, viz. Clupea harengus , of seven different scales of maturity. Most 

 of the authors certainly do not bring in any new facts, and their scales are not essentially different 

 from the scheme of Heincke , 



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