Cephalothrix linearis, light micrographs of Azan stained transverse sections of the brain.

a: The 4 cephalic cords (cc) are frontally covered by an enormous layer of cell somata (cs). b: The brain (br) is composed of a central neuropil (np) surrounded by cell somata (cs). The somata are separated from the neuropil by an inner neurilemma (in). A ventral commissural tract (vct) connects the two parts of the brain. c: The posterior part of the brain is divided into dorsal (dl) and ventral (vl) lobes. d: the ventral lobes are confluent with the lateral medullary cords (mc), two proboscidial nerves (pn) and esophageal nerves (en) are present. A dorsal nerve (dn) extends to the posterior underneath the basal lamina of the epidermis. fg foregut.