Figure 10

Organization of the dorsal ganglion in 3-day-old juvenile of Phoronopsis harmeri . Cross semithin (A) and thin (B-D) sections of the head region. (A) Two dorsolateral groups of perikarya (pink boxes) connect via thick commissure. (B) A portion of one of the dorsolateral group of perikarya: sensory (blue) and nonsensory (pink) perikarya are visible. Perikarya of both types bear centrioles (arrowheads). (C) A portion of the commissure, which consists of nerve fibers of different types. (D) A proximal portion of the giant nerve fiber associated with epidermal cell (blue), which contacts the epidermis surface and bears the centriole (arrowhead). Abbreviations: bl – basal lamina; c – commissure; c2 – mesocoel; cc – coelomic lining; cv – clear (electron-lucent) synaptic vesicle; dcv – dense-core vesicle; er – erythrocyte; es – esophagus; G – Golgi apparatus; gf – giant nerve fiber; m – mouth; mc – mitochondria; mi – microvilli; mnr – minor nerve ring; mt – microtubule; n – nucleus; nf – nerve fiber; tt – telotroch.