1. The basophilic granule of blood and marrow cells does not show the brown color reaction with benzidine solutions that is characteristic of the neutrophilic and eosinophilic granules. It differs from these types also in other important microchemical and physical particulars. 2. The hemic basophil which bears these granules is peculiar from a purely cytological standpoint, while physiologically it appears to be devoid of any functional activity comparable with that of the other granulocytes. 3. The peculiarities exhibited seem in every instance, at least for mammalian blood, best explained as evidence that the basophil is a degenerated or degenerating cell. It is probably derived from the eosinophilic cells and perhaps in rare cases from those of neutrophilic type.