Snark Eggs are stationary alien organisms filled with Snarks. They consist of a spherical body hung in mid-air with a yellow laser beam projecting out of its top and two other purple beams randomly emitting from its sides. If the player touches the object or crosses one of the purple beams, the Egg explodes and releases Snarks.
Snark Eggs appear only in the chapter "Forget About Freeman!". Several block an optional path that leads to an area with supplies which is also covered with web-like alien materials. The player has to destroy one egg that blocks the entrance to the canals in order to progress.
Behind the scenes
It is speculated that Snark Eggs may be biological bombs installed by the members of the Xen military as traps. This, however, remains unconfirmed.