It is well known that the astrocytomas differ histologically among themselves, and that this difference in structure, in what appears to be a relatively uniform group of tumors, may sometimes be surprisingly great. This has been apparent to one of us for some time, since a routine study of these tumors will soon convince anyone of their variation in structure. This observation is by no means new, for Cushing and Bailey (1) in their original descriptions recognized both a fibrillary and protoplasmic type of astrocytoma, each with its more or less clearly defined clinical syndrome. That this is not all that can be said for a differentiation of the astrocytomas seems to be clear.