The cerebellar vermis can be seen in this bisected brain. The vermis is composed of about a dozen lobules, separated by fissures. The most caudal lobule is the nodulus. The primary fissure is the embryonic first fissure, and it is the deepest fissure. The primary fissure divides the cerebellum into a rostral lobe and a caudal lobe. (The nodulus and the two flocculi constitute a third lobe.)