The amniote chicken egg looks unassuming, but is extremely cool. It contains a huge single-celled yolk (the ovum) and enough water and nutrients to support the developing chick until it hatches. Around 350 BC, Aristotle studied the embryonic development of Gallus gallus, or the domestic chicken, by cracking open an egg every day during the three-week incubation period. He was the earliest known embryologist. Ever since then, the domestic chicken has been a favorite model for studying vertebrate development. In 1951, Hamburger and Hamilton took extremely detailed photos of chick development and assigned stages to each visible step in the process. Below are pictures of embryonic chicks at various HH stages of development (HH = Hamburger and Hamilton), labeled by budding embryologists in the Swarthmore Developmental Biology class.

Our Chick Embryo Pictures!

Figure 1. HH Stage 4 -- Definitive primitive streak. Labeled by Lauren Fety.	Figure 2. HH Stage 11 -- Thirteen somites; five neuromeres of hindbrain. Labeled by Laura Twichell.
Figure 3. HH Stage 20 -- 40-43 somites; rotation completed; eye pigment. Labeled by Jake Beckman.	Figure 4. HH Stage 25 -- Elbow and knee joints. Labeled by Ann Marie Lam.
Figure 5. HH Stage 25 -- Elbow and knee joints. Labeled by Mari Velez.	Figure 6. HH Stage 26 -- First three toes. Labeled by Anisha Chandra.

Go to the References and Cool Links Page!

© Anisha Chandra, Swarthmore College, 2004