Sheer (biology)
Sheer is a method by which the insides of eggs can be assessed. The term comes from Low German and means pure (in the sense of uniform, clean).
The primary purpose of this screening is to identify unfertilized or dead eggs in order to separate them from those with well-developed embryos . For this purpose, the eggs are usually placed in a darkened room on what is known as a skier lamp, which makes structures inside the egg visible in transmitted light without heating the egg.