The extent of the floor-plate of His and its significance.The summary of this paper is as follows: 1. A differentiated floor-plate extends no farther cephalad than the fovea isthmi. Increased morphologic significance is believed t o attach to this depression. 2. The plan of arrangement of the longitudinal zones of His as set forth by him and generally accepted is interpreted as giving a wrong morphologic basis for the brain. 3. Theoretic considerations based partly on the 'blastopore theory' indicate: a) that the floor-plate corresponds to a 'sutura neurochordalis' (His) ; b) that the floor-plate and notochordal plate are primarily coextensive; c) that the neurochordal suture does not extend to the anterior end of the neural plate; d) that the primary motor and sensory zones are continuous from side to side cephalad of the anterior end of the floor-plate. 4. The following interpretations are accepted: a) that the optic chiasma marks the anterior end of the neural plate; b) that the motor zone terminates with the midbrain; c) that the floor-plate terminates at the fovea isthmi; d) that the boundary between motor a n d sensory zones terminates near the mammillary recess. 5 . A rational basis for the division of the brain into epichordal and prechordal portions is afforded by the interpretation presented. 6. A number of facts of cephalic and encephalic morphology may be better interpreted on the basis suggested in this paper.

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The following is a preliminary communication of the results ohtained by us in a study of the relations and connections of the sound-transinitting apparatus in certain American Urodeles.Since it is in the class Amphibia that a sound-transmitting apparatus first appears, a knowledge of the relations liere is of double value,-in aiding the interpretation of homologies in the lower forms (fishes), and in contributing toward the solution of the difficult questions surrounding the significance of the reptilian coluiiiella and the auditory ossicles of the Mammalia. Furthermore, the functioii of the Amphihian columella is unknown, and as a preliminary to esperiinental work its relations in a large series of forms were ascertained.Gauppl has alreadj-called attention to the apparently different relation that the coluniella has to other structures in Urocleles, which led him to beliere that there were two different connections of this element found in these forms, and later? he restated this opinion. Driiner3 has

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