The hemicycle design is a compromise between the different Parliamentary systems.
From the en.wikipedia.org
Thus, the session starting on 1 September was moved to the Brussels hemicycle.
From the en.wikipedia.org
A speech by Obama in the hemicycle could add greatly to that informal power.
From the economist.com
Three quarters of Parliament now takes place at its Brussels hemicycle.
From the en.wikipedia.org
John Paul continued with his address after Paisley was ejected from the hemicycle by fellow MEPs.
From the en.wikipedia.org
Both the Brussels and Strasbourg hemicycle roughly follow this layout with only minor differences.
From the en.wikipedia.org
The parliament wants President Barack Obama to visit them, and speak to all Europe from its hemicycle.
From the economist.com
Due to the new members, the Parliament needed a larger hemicycle to hold debates, and more offices for MEPs.
From the en.wikipedia.org
While this is not direct evidence, is does suggest that the hemicycle remains in the comitium of Rome are what is left of a similar structure.
From the en.wikipedia.org
More examples
Semicircle: a plane figure with the shape of half a circle
In legislatures, a hemicycle is a term for a semicircular, or horseshoe shaped, debating chamber (plenary chamber) where deputies (members) sit to discuss and pass legislation. Though composed of Greek roots, the term is French in origin. It may also be known as an amphitheatre.
The group of columns, arranged in a semicircular formation, that divide the east end of a choir from the ambulatory.