A brain-Hatschek's pit connection in amphioxus.

In the adult lancelet, Branchiostoma belcheri, there is a lobe of the right ventral margin of the brain that extends around the right side of the notochord and makes contact with Hatschek's pit, which also is to the right of the midline. This structural system resembles the hypothalamo-adenohypophyseal system of vertebrates and appears to make possible seasonal nervous regulation of the release of gonadotropin. Copyright 1999 Academic Press.