1 2 3


4. 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 forceps.

5. Drop a filter paper disc around your embryo. Hold on to the filter
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.

6. 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.

7. For each embryo,determine the H&H stage. How do these embryos compare to
the stained specimens?

8. 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.

3-day chick embryo

Instructor's prep list

©Cebra-Thomas, 2000

Last Modified: 13 April 2000

[Lab Protocols | Students | Cebra-Thomas | Course | Links ]