¢ 
May 22, 1873] 
NATURE 
69 
A towing-net dragged by means of a line from the 
side or stern of the boat may be used, but is not so 
much under control, and seldom produces so much spoil : 
such a net, however, attached in a tide-way during the 
night to some stationary object, and made with the pre- 
cautions mentioned above, will often do good work, es- 
pecially if its specific gravity be adjusted so as to sink 
very slightly below the surface. As a rule, indeed, the 
hours from dusk to midnight seem to be the best for cap- 
turing pelagic species near the surface. In tidal pools on 
the shore the same appliances are required as for fresh- 
water ponds, : 
Ostracoda and other deep-dwelling species’ require, of 
course, the use of the dredge ; and where Microzoa only 
are the objects sought, the dredge may conveniently be 
made of a size much smaller than those in ordinary use. 
The mouth need not be more than 6in. in its largest 
diameter, the bag being made of coarse canvas or “ cheese 
cloth,” and from 18in. to 2ft. long. The material so 
dredged up, after having been passed through suitable 
sieves, so as to separate the coarser portions, should be 
washed in a muslin bag for the purpose of removing all 
the impalpable mud, which often constitutes a very con- 
siderable proportion of the bulk : this operation may most 
easily be performed over the side of the boat in the sea, 
or in some large vessel of sea-water. The washed mate- 
rial is then to be put up in canvas bags, duly labelled, and 
hung up in a warm position to dry ; the more rapidly this 
part of the process is conducted the better chance will 
there be of preserving the internal parts, as ‘well as the 
valves of the Ostracoda, in good condition. But should 
it be wished to secure the animals actually alive, the best 
plan will be, after washing the mud as above explained, 
to immerse a quantity of it in a basin of sea water, allow- 
ing it to stand for an hour or more, when many of its 
inhabitants will have made their way to the surface of the 
water. They will, indeed, continue to come to the surface 
for many hours, but the later ones will probably be sickly 
or dead. 
But besides Ostracoda, there are often great numbers 
of Copepoda in or on the ooze and sand of the sea-bed. 
These require for their separation a different method of 
procedure ; the following, so far as I know, being the 
most convenient. After the process of sieving described 
in the preceding paragraph, all the minute swimming 
animals will be found in the water in which that operation 
has been conducted ; all that is necessary, therefore, is to 
pour the water off through a muslin net in which the 
Microzoa will be retained—in a dirty state, however, 
which will render careful washing desirable, or still 
better, the transference of the whole to a bottle of clean 
sea water for an hour or two; in this way the little crea- 
tures will clear themselves of adherent dirt better than we 
can do by any amount of washing. 
Avery rich field for the collecting of Copepoda is found 
in the groves of Fuci and Laminariz so common on rocky 
shores at and beyond low-water mark. The fronds of 
these weeds having been dragged up in any convenient way, 
are to be .washed, a handful or two at a time, by brisk 
agitation in a tub of sea water, after which the water is to 
be filtered as directed above. It is best not to macerate 
weeds in the water for any great length of time, because 
much mucus exudes from the Laminariz, enveloping the 
Entomostraca, and rendering it an extremely difficult and 
tedious matter to examine the gathering properly. It 
should be mentioned that, although all weeds harbour 
numbers of Entomostraca, Laminaria saccharina is, as 
a rule, by far the most productive, apparently on account 
of the rugosities of the frond affording more efficient shel- 
ter to their minute inhabitants ; sheltered pieces of coast 
and land-locked bays are much the most productive 
hunting grounds, 
Treatment of Dredged Material—The separation of 
Ostracoda, Foraminifera,and other Microzoa from dredged 
sand or mud, is best accomplished by the process of 
“floating.” For this purpose the material should be 
thoroughly well dried and sifted, so as to insure the fine 
division of the whole mass, then placed in a vessel of 
water and thoroughly stirred. By this means all the 
lighter organised particles—chiefly Ostracoda, Forarnini- 
fera, minute Mollusca, fragments of Polyzoa, &c.—will, 
owing to their contained air, be brought to the surface, 
and may be removed in any convenient way, but best, 
perhaps, by pouring off the supernatant water through a 
very fine gauz2 sieve. Some of the larger and heavier 
species will, however, sometimes remain at the bottom, 
and must be picked out with the help of a hand lens. 
Fossiliferous Clays and Shales.—These, after repeated 
maceration in water, should be passed, time after time, 
through fine sieves, so as to wash out the impalpable sus- 
pended mud ; at last drying the residuum and floating 
out the organic particles, as previously directed. When 
much fossilised, however, the Microzoa will not float. In 
this case they must be picked out one by one from the 
residuum left after the repeated washings. 
Preservation of Specimens,—Soft-bodied species, ¢.g., 
Copepoda, Cladocera, &c.,are best preserved in methylated 
spirit, either of full strength or diluted with anequal quantity 
of water, the latter, in my opinion, being preferable, as it 
does not so readily evaporate entirely if left unattended to 
in small bottles fora length of time. . The great disadvan- 
tage of alcohol is that it coagulates the albuminous tissues, 
rendering the animals almost opaque, at the same time 
destroying the natural colour ; but most other preserva- 
tive solutions possess these properties to a greater or less 
extent, and have likewise other drawbacks, such, for 
instance, as becoming cloudy, permitting the growth of 
fungi, &c. When, however, it is especially wished to 
preserve the colours, a mixture of equal parts of glycerine 
and distilled water answers admirably. Indeed, the only 
hindrances to its general use as a preservative for Micro- 
zoa are its strongly solvent action on calcareous tissues 
and its inconvenient stickiness. For microscopic mount- 
ings (of non-calcareous objects) some kind of “ glycerine 
jelly” answers admirably ; especially that described by 
Dr. Carpenter in his book on the microscope, which 
preparation is, however, improved by saturating with 
arsenious acid the water used in its manufacture. Ostra- 
coda and other dry specimens require, of course, no 
preparation beyond mounting on slides of wood or card- 
board. An excellent plan of mounting, so as to show at 
one view all the Ostracoda or Foraminifera obtained in 
any locality, is shown in the accompanying diagram, the 
Orr MarspDEN, 10 FATHOMS. 
Muppy Sanp. 
slides being made of the ordinary size, of stout card- 
board or millboard. The central part of the slide is cut 
out, and the marginal portion mounted on another slide’ 
having a dull black ground. The slide is ruled trans- 
versely, so as to divide it into any convenient number of 
spaces, and if needful, ruled also with one line length- 
wise down the middle. Each space is marked with a. 
figure or letter of the alphabet referring to the species 
mounted within it, and an index to the whole kept in a 
book of reference. The diagram is a facsimile of a 
mounting so prepared in my collection. 
GEORGE S, BRADY 
