The groups of experiments herein reported were carried out in order to determine what connection the superior olive makes with other centers through the olivary peduncle. An abstract of this work appeared in theAnatomical Record.1The experiments were undertaken with the supposition that the superior olive probably does send fibers into the reticular formation which make connections with various motor centers in addition to the usual connections believed to exist with the nucleus of the abducens nerve. In the cat (fig. 3), the superior olive consists of a large lateral S-shaped segment and a smaller medial or accessory segment which is a straight piece. Ventral to these are the preolivary nuclei of Cajal,2and medial to them in the trapezoid body is the nucleus of the trapezoid body. I have adopted these terms because there is evidence that the (medial) nucleus of the trapezoid body differs essentially