38
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
in a tall, narrow glass jar and the water in it is thoroughly agitated
with a perforated plastic plunger to distribute the eggs uniformly.
A sample is then taken with a volumetric pipette, and the number of
eggs or larvae per ml is determined by counting them on a SedgwickRafter cell. After that the eggs or larvae are again agitated, to ensure
their even distribution in the vessel, and the necessary volumes of
water carrykg larvae are transferred to culture vessels.
We usually begin our experiments with 10 000 to 15 000 straighthinge larvae per liter of sea water. However, because not all fertilized
eggs develop into normal larvae, it is our practice to piace approximately twice this number of eggs into each culture vessel to produce a
sufficient number of larvae. Accordingly, about 30000 eggs per liter
are used in starting cultures. These eggs are placed in containers
filled with 8ea water that is first filtered through an Orlon filter and
then subjected to the sterilizing action of ultraviolet rays. The eggs
are then left to develop undisturbed for 48 hr and no food is added
during this period.
All culture vessels are immersed in a common water bath table,
the temperature of which is controlled within f I.O"C (Figs. 5 and 6).
Usually, neither aeration nor mechanical agitation is employed because
we have established that clean, well-attended cultures do not require
aeration if the water is changed every second day. I n special experiments requiring mechanical agitation we use a number of devices,
including a rotating wheel, paddle-agitator (Fig. 51, or regular shaking
machine.
At the end of 48 hr young larvae, now protected by fully formed
shells, are collected by screening the cultures through sieves having
325 meshes per lineal inch (44 p opening). Larvae retained by the
screen are gently washed and placed in a tall jar. Using the same
method as that employed with eggs, the number of larvae per ml is
determined, and the appropriate volumes of water containing larvae
are placed in each culture jar to create desired concentrations.
Samples of larvae are taken whenever needed, usually at 2-day
intervals. This is again accomplished by collecting all larvae from a
container on a 325-mesh screen and then transferring them to a
graduated cylinder of I-liter capacity from which, after proper
agitation, required samples are taken, while the remaining larvae are
returned to the culture vessel.
D. Larval period
morphosis is affected by many conditions.
Rate of growth of veligers from straight-hinge stage to metaI n our laboratory work
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
in a tall, narrow glass jar and the water in it is thoroughly agitated
with a perforated plastic plunger to distribute the eggs uniformly.
A sample is then taken with a volumetric pipette, and the number of
eggs or larvae per ml is determined by counting them on a SedgwickRafter cell. After that the eggs or larvae are again agitated, to ensure
their even distribution in the vessel, and the necessary volumes of
water carrykg larvae are transferred to culture vessels.
We usually begin our experiments with 10 000 to 15 000 straighthinge larvae per liter of sea water. However, because not all fertilized
eggs develop into normal larvae, it is our practice to piace approximately twice this number of eggs into each culture vessel to produce a
sufficient number of larvae. Accordingly, about 30000 eggs per liter
are used in starting cultures. These eggs are placed in containers
filled with 8ea water that is first filtered through an Orlon filter and
then subjected to the sterilizing action of ultraviolet rays. The eggs
are then left to develop undisturbed for 48 hr and no food is added
during this period.
All culture vessels are immersed in a common water bath table,
the temperature of which is controlled within f I.O"C (Figs. 5 and 6).
Usually, neither aeration nor mechanical agitation is employed because
we have established that clean, well-attended cultures do not require
aeration if the water is changed every second day. I n special experiments requiring mechanical agitation we use a number of devices,
including a rotating wheel, paddle-agitator (Fig. 51, or regular shaking
machine.
At the end of 48 hr young larvae, now protected by fully formed
shells, are collected by screening the cultures through sieves having
325 meshes per lineal inch (44 p opening). Larvae retained by the
screen are gently washed and placed in a tall jar. Using the same
method as that employed with eggs, the number of larvae per ml is
determined, and the appropriate volumes of water containing larvae
are placed in each culture jar to create desired concentrations.
Samples of larvae are taken whenever needed, usually at 2-day
intervals. This is again accomplished by collecting all larvae from a
container on a 325-mesh screen and then transferring them to a
graduated cylinder of I-liter capacity from which, after proper
agitation, required samples are taken, while the remaining larvae are
returned to the culture vessel.
D. Larval period
morphosis is affected by many conditions.
Rate of growth of veligers from straight-hinge stage to metaI n our laboratory work