Isolate a 1- or 2-day embryo. Clean your dissecting
equipment and prepare a fresh
dish of Howard's. Clean an
egg and allow the embryo to float to the top.
Open the blunt end of the
egg and remove the shell membranes. the embryo
may not be visible to the
naked eye. The blastodisc is located above a small ring
of white yolk. Remove
albumin with wide-mouth pipet and shell with
Drop a filter paper disc around your embryo. Hold on to the
paper with fine forceps and
cut around the ring with your sharp scissors.
Transfer the embryo to a
small petri dish with Howard's Ringer's solution.
Examine both embryos. Pay particular attention to the heart
and circulation, and
to the developing neural
tube. Compare the heart rate between the 2 embryos.
Which side was towards the
yolk? The reddish spots on the 2-day blastodisc are
the blood islands, the sites
of hematopoesis. The embryo is covered with a clear
protein layer known as the
vitelline membrane. This may start to peel away
from the embryo.
For each embryo,determine the
stage. How do these embryos
Clean your instruments well with warm water, distilled water
and 70% ethanol.
Dry before returning to
case. Discard the shells and the yolk/albumin remains.