The vibrissae of the California sea lion are richly innervated with myelinated fibers that terminate in three distinctly different endings. Large nerve bundles enter the base of the follicle and immediately branch into smaller bundles that traverse the connective tissue trabeculae below the large ring sinus. Some neurons terminate in a lamellated corpuscle in close relationship to the venous sinuses of the proximal cavernous tissues. The remainder of the nerves continue distally parallel to the glassy membrane terminating in two specific types of endings arranged in a ring about the shaft of the vibrissae at the level of the upper portion of the ring sinus. One type of ending is on the outer surface of the glassy membrane where the myelin sheath terminates abruptly and the sensory ending is flattened into a thick, lancet-shaped structure. A n extension of cytoplasm from a specialized supportive cell covers this terminal segment of the nerve on two sides, while numerous finger-like extensions protrude into the connective tissue from the narrow, uncovered sides. The second type of ending penetrates the glassy membrane, branches, and terminates in close apposition to the Merkel cells in the outer root sheath. Amyelinated nerves of various sizes are frequently observed in the same bundles as the larger myelinated fibers, but to date, the position of their termination has not been established.

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The Poulter seismic method is outlined and an analysis is made of the frequency distribution of seismic energy from different sources. The effect of different sources upon the directivity of the energy in the ground and the improvement that can be obtained in signal‐to‐noise ratio is discussed. Three different methods are described for controlling the frequency of the seismic impulses being introduced into the ground and the resulting improvement in the quality of records is illustrated. The almost complete elimination of multiple reflections by the method is indicated.

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