CHAP. VI. ] DEEP-SEA DREDGING. 261 
water. It is of great importance not to give any 
rotatory motion to the sieves in this part of the 
process, for such is very ruinous to fragile organisms. 
The sieves should be gently churned up and down, 
whether singly or together. The result, of course, is 
that the rougher stones and gravel and the larger 
organisms are washed and retained in the upper 
sieve. The fine mud or sand passes through the 
_whole of the sieves and subsides into the bottom of 
the tub, while the three remaining sieves contain, in 
graduated series, the objects of intermediate size. 
The sieves are examined carefully in succession, and 
the organisms which they contain gently removed 
with a pair of brass or bone forceps into the jars 
of sea-water, or placed at once in bottles of weak 
spirit of wine. 
The scientific value of a dredging operation de- 
pends mainly upon two things,—the care with which 
the objects procured are preserved and labelled for 
future identification and reference, and the accuracy 
with which all the circumstances of the dredging, 
position, depth, nature of ground, bottom tempera- 
ture, date, &c., are recorded. With regard to the 
preservation of the animals, I cannot here go into 
detail. There are many ways of preserving, special 
to the different invertebrate groups; and ‘ taxi- 
dermy ’ is in itself a complicated art. I will merely 
mention one or two general points. A specimen in 
almost every group is of infinitely greater scientific 
value if it be preserved entire with its soft parts. 
For this purpose the most usual plan is to place it 
at once in spirit of wine diluted to about proof. 
Care must be taken not to put too many specimens 
