1010 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [10] 
fine gauze, weighted with a stone ora piece of lead, the net is let down 
te a limited depth, and left under water a shorter or longer time—say 5 
to 10 minutes—according to the force of the current and the swiftness 
of the boat. Even ata moderate rate of speed the net tightens, and 
everything which fioats into it is retained by the fine meshes. A piece 
of wire-grating closes the opening of the net to larger objects. Draw- 
ing it carefully out of the water it is turned inside out into a wide glass 
jar with fresh sea-water. Aiter having, by microscopic observations, 
obtained a general idea of the various animal forms contained in the 
water, it is not difficult to distinguish them from each other, with the 
naked eye or with a magnifying glass, particularly by their different 
motions. 
“During my first experiments with the above described net I found it 
to be extremely well suited to my purpose. ‘This was, in the first place, 
to find the proportion of oyster larve floating near the surface, in deeper 
water, and immediately above the bottom, at different times, and in 
as many places as possible. It seemed important to me to get an idea 
of this proportion, especially in connection with the following consid- 
erations. 
“The swiftness with which the oyster larva moves about by means of 
the thread-like apparatus, is very insignificant as compared with the 
swiftness of the current of the tide when coming in or going out. As 
regards the radius of distribution of the oyster spat, it is entirely 
dependent on the varying swiftness of the current. Inthe river Scheldt, 
where natural and artificial oyster beds are scattered all over the river, 
oyster spat is probably floating about everywhere as soon as the time 
has arrived for the spat to become detached from the mother oyster. 
Whether oyster spat will settle more freely in one place than in another 
will, therefore, depend not so much on the radius of distribution of the 
oyster larvee of this or that oyster bed as on the peculiar conditions of 
the current. It is, therefore, in the first place, necessary to learn to 
know the swiftness and direction of the currents in the principal por- 
tions of the river Scheldt, and it is consequently a matter for which we 
are very thankful that the minister of public works has given his sup- 
port so freely to this part of our observations. A thorough knowledge 
of the currents, combined with practical experience, will give us a better 
insight into the reason why certain localities are better adapted to the 
settling of the oyster spat than others. In studying this subject, spe- 
cial attention should be paid to the manner in which the oyster larvee are 
distributed over the different depths of water, as unfortunately but 
little is known at present concerning this important matter. Although 
their organs of motion do not enable them to go any great distance— 
which, moreover, is not essential to their distribution—these organs, 
nevertheless, furnish them with an entirely satisfactory power of rising 
and sinking, and of keeping themselves afloat in the water when it is 
not violently agitated. In connection with the conditions of current 
