. The Journal of comparative neurology and psychology. arther laterally. In brief,in selachians the cells are much more numerous, extend the wholelength of the tectum and the largest collection is in the posteriorregion; in ganoids and teleosts the cells are fewer, are confined tothe anterior half of the tectum and are collected chiefly at the 6o4 Journal of Comparative Neurology and Psychology. anterior border. In fishes I have seen none of the large cells alongthe course of this bundle caudal to the velum medullare Necturus the cells are found throughout the length of thetectum,
. The Journal of comparative neurology and psychology. arther laterally. In brief,in selachians the cells are much more numerous, extend the wholelength of the tectum and the largest collection is in the posteriorregion; in ganoids and teleosts the cells are fewer, are confined tothe anterior half of the tectum and are collected chiefly at the 6o4 Journal of Comparative Neurology and Psychology. anterior border. In fishes I have seen none of the large cells alongthe course of this bundle caudal to the velum medullare Necturus the cells are found throughout the length of thetectum, are most numerous in the posterior part and are very fewnear the anterior border. Except near the anterior border, everytransverse section of the tectum shows from three to six of thesecells and one or two of the number are situated laterally, somewherewithin the medial one-half of the tectum. One cell was seen at thelateral border of the tectum. In Cryptol^ranchus the arrangement issimilar, but the greater number of cells are in the anterior half of. Fig. G. a, trausverse section of the uiesencephalon of the toad. A sectiontluougli the anterior part of the lateral cavities was drawn and the cellsinserted under the camera from several sections farther forward. The cellsnear the middle lie in the section outlined, those at the sides mostly lie infront of the lateral cavities. B, three sections through the posterior, middleand anterior parts of the tectum of Scyllium. Only the outline of the aqueductis drawn and the cells in their proper position with reference to it. the tectum, while in the posterior half the cells are more strictlygrouped at the median line, i. e., in the roof plate. In the frog thecells are fewer in number and, so far as I have seen, are placed farlaterally in the dome-shaped tectum. In the toad the cells are muchmore numerous than in the frog. They are situated in the anteriorpart of the tectum, there being two large groups in the anteriorbulging wall of the
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