de 
largely to the elucidation of the migrations of the herring. It will here suffice to men- 
tion that it proved possible to determine, that the herrmg along the hundred fathom 
curve consist for the most part of Norwegian fish, with occasional admixture of Shet- 
land herring, which as a rule keep to the west of the bank. Fig. 31 shows the fishing 
grounds where one of the larger series of experiments was made, in 1905. The herring 
here were found, when taken in on the bank, Stations 3—16, in the autumn (August- 
November) for the most part in spent condition, whereas the herrmg on the Revkant, 
Stations 17—36, exhibited genitals in a far less developed state of maturity. Even late 
in the autumn, for instance at the end of October, the ovaries were found to be at stage 
III*). The first group belong to the summer spawning Shetland herring, the last to 
the Norwegian spring spawning fish. 
a 183 23 
& ART ER 
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SALUT 
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à be EAP 
100 
aw 
CA e9vit @ 36x 
nz oldvn rn 35x 
2e HE 2° 3 
Fig. 31. Grounds worked by the cutter ‘“Fridtjof”, 1905. 
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“avn 
0° 
1 40 
The study of herring from the Dogger Bank and Skagerak also furnished consider- 
able information as to the composition of the samples; it appeared, however, very desir- 
able to check these results by comparison with HEınckeE’s methods of investigation. 
*) As regards maturity, the following 7 stages have been fixed, chiefly on the basis of a 
suggestion made by HEıncke. 
Stage I. Immature fish which have never spawned, with very small genitals immediately 
below the spinal column. The female exhibits claret coloured, torpedo-shaped ovaries about 
2—3 cm. long and 2—3 mm. thick. No. eggs visible to the naked eye. The male has whitish or 
greyish brown knife-shaped testicles, 2—3 cm. long and 2—3 mm. broad. 
Stage II includes both immature fish with genitals beginning to develope, and spent fish with 
genitals beginning to prepare for a new spawning. Ovaries somewhat more than half the length 
of the abdominal cavity, about 1 cm. in diameter. Eggs small, but visible to the naked eye. 
Testicles of the male are whitish, with some blood-red spots, and of the same size as the ovaries. 
Stage III. Genitals thicker, or swollen, occupying about the half of the whole abdominal cavity. 
Stage IV. Genitals occupy ?/; of the abdominal cavity. Eggs not yet transparent; milt 
white and swollen. 
