The fine structure of spermatids and spermatozoa of the soil mite Caloglyphus anomalus was observed. Early spermatids contain mitochondria, Golgi complexes, endoplasmic reticulum, and free ribosomes. During spermiogenesis chromatin condenses into 200–300 A thick threads, the nuclear membrane disappears and a highly folded surface membrane forms as an endoplasmic reticulum and/or Golgi complex derivative. In late spermatids inner portions of the surface folds sink into the cytoplasm and are found in mature spermatozoa as membrane sheets situated in concentric whorls around the chromatin threads. These observations are compared to previous fine structure studies on grain mite spermatozoa and spermatozoa wherein similar nucleocytoplasmic mixing and internalized membrane formations occur in efforts to demonstrate its possible significance in these unusual type spermatozoa. Assuming that these spermatozoa are not degenerative or otherwise nonfunctional, this is another example of an unusual nonflagellate type spermatozoa similar to closely related arachnids and crustacea.