SEA-FISHERIES LABORATORY. 319 
clogged by an abundant haul of Medusae, or Phacocystis, 
or Chactoceros, that it will only let the water through very 
slowly even when suspended in air. Such a net cannot 
have been filtering satisfactorily during its last haul, and 
it is very difficult to get the meshes thoroughly cleaned. 
The filtration coefficient of a net must thus vary not only 
with age, but to some extent with every individual catch 
that is made, and even possibly with the effect produced 
by previous catches. 
SURFACE AND Derrer Nets. 
On the whole, the results obtained in 1908 confirm 
those noted in the report for 1907. Again the weight net 
(an all other respects agreeing with the fine surface net) 
lowered to a depth of about ten fathoms and gradually 
rising to a depth of a fathom or two below the surface, 
gave in most cases a larger haul than the similar surface 
net. ‘The various points mentioned in last year’s report 
could again be exemplified from the 1908 forms; but it 
seems unnecessary to repeat what has already been 
demonstrated. | 
Form No. 10 is rather interesting, as showing a 
contrast between the surface and the deeper nets at a point 
just outside the bay to the north. It also shows a haul 
taken on the same day inside the bay, and illustrates what 
is often seen, namely, that the plankton is larger in 
amount inside the bay than outside, ‘he surface net mm 
the bay obtained as much material as the weight net 
outside. It will be noticed that few Dinoflagellata were 
obtained in the weight net, and that more were present 
inside the bay than outside. It is also noticeable that no 
adult Copepods were obtained on this occasion in the bay, 
while all three nets outside obtained some. 
Form 23, dealing with the gathering taken off 
