1. We have studied the brain stems of kalong, tuber-nosed bat, greater horseshoe bat and vampire bat, all belonging to the order of Chiroptera, and have found that the former two (A-group) showed considerably contrasting findings to the latter two (B-group).
2. In A-group, the pyramidal tract is very strongly developed and the solitary tract seems to be in somewhat better development than in B-group. In the latter group, the pyramidal tract is so weakly developed so as to appear rudimentary, but the solitary tract is only a trifle poorer than in A-group.
3. The genu, in A-group, runs along the medial side of the abducens nucleus and is of considerable length, while in B-group, it runs levels far more cranial than the abducens nucleus along the lateral side of the position taken in by the abducens nucleus in the caudal sections and is much shorter than in A-group.
4. The facial nucleus occupies about the same position near the ventral edge of the sections, both in A-group, where the pyramidal tract is strongly developed and in B-group, where the tract is only rudimentary.
5. As detailed in the discussion above, our findings confirmed us in the difficulty of our accepting the KAPPERS' so-called neurobiotaxis theory.