Fig. 154.—Transverse Section through Auditory Capsules and Brain of Ammocœtes. "Au.", auditory organ; "VIII", auditory nerve; "gl.", ganglion cells of VIIIth nerve; "Au. cart.", cartilaginous auditory capsule; "gen.", cells of old generative tissue round brain and in auditory capsule; "bl.", blood-vessels (All references in this work to "Ammocœtes" or "Petromyzon" appear to refer to the European Brook Lamprey, now called "Lampetra planeri".)