IMIS

By electron microscopy of the coxal gills in two species of estuarine amphipod crustaceans, Grandidierella japonica and Melita satifragella, we found a patch-like, specialized tissue area which consisted of unique cells closely resembling the salt-excreting cells in the gill of the brine shrimp and so-called chloride cells in teleost gills. These cells were characterized by an abundance of mitochondria, two kinds of extensive networks of cytoplasmic tubules, well-developed lamellar infoldings of the basal cell membrane, sparse microvillous projections of the apical border, and numerous large vacuoles with several incomplete partitions. The large (60 nm in diameter) and the small (30 nm) cytoplasmic tubular networks were found in the basal and the apical portions of the cell, respectively. The large networks, which were both directly and indirectly (through the lamellar system) continuous with the basal cell membrane, were regarded as extensions of the cell membrane. Both the outer walls and the partition walls of the vacuoles were reinforced with a parallel array of microtubules.