OF THE GRIMSBY TRAWL FISHERY. 393 
mature brill in the catches on Hastern grounds to be a very small 
one ; but it varies considerably, since occasionally a very marked 
number of sexually immature forms will be taken. Many immature 
fish are sometimes caught on a shallow ground near Mablethorpe in 
Lincolnshire. On the offshore grounds in any part of the North 
Sea comparatively few immature fish seem to occur. 
The distribution of the sole in the North Sea is so far capable of 
more or less exact definition, in that there is a large area in which 
soles are at ail events very scarce. The species is very rare in 
Scotch waters, but occurs more plentifully southwards along the 
east coast of England. It is found also on the grounds lying off 
the coast of Denmark, and southwards along the Continental margin, 
also in the central parts of the North Sea, south of a line which 
may be drawn across so as to follow the southern edge of the 
Dogger Bank. Thus the Dogger and all the central area of the 
North Sea northwards of this bank may be eliminated as practically 
devoid of soles. None are found, I believe, on the coast of Norway, 
and, indeed, the channel of very deep water which follows the Nor- 
wegian coast-line seems to act as a boundary impassable to all but 
the bathybial* flat-fish, That it should be so by the adults is 
intelligible enough, but it is not so clear why the pelagic ova and 
larvee should not crossit. That they do not do so to any appreciable 
extent is rendered extremely probable by the marked structural 
differences which one finds to exist between the Norwegian turbot 
and their brethren of the North Sea. 
The sole spawns in the North Sea chiefly in May and June, 
though the whole period may extend from April to August. 
Spawning on our own coasts takes, place chiefly on the offshore 
grounds, always in water of some depth, and away from the 
chief haunts of young flat-fish ; but on the Hastern side a great 
deal of spawning is done on the small-fish grounds. Of the very 
young stages I know but little from my own observations, having 
only obtained a few recently hatched larve in the tow-nets. The 
later metamorphosing stages I have never found, either in the 
North Sea or elsewhere, but specimens of about half an inch long 
have been found by Mr. Cunningham between tide-marks in 
Mevagissey Harbour. Soles of about an inch and a half in length 
begin to appear in the Humber in the summer, though not to my know- 
ledge at the extreme margin, but specimens from about two and a 
half to four inches are not infrequent at the margin from spring to 
autumn, and occur also, as I understand, in similar situations 
further south along the Lincolnshire coast. I do not know that 
* The halibut, witch, and megrim are the only North Sea flat-fish of any importance 
which regularly descend to great depths, aud are thus “ bathybial ” in habit. 
