Appearance of perichromatin granules in decondensing sperm nuclei in fertilized mouse eggs.

A number of granular structures measuring about 35-45 nm in diameter appeared in the dispersing chromatin materials of the decondensing sperm nuclei in fertilized mouse eggs. These granules were contrasted by the bismuth staining en bloc following either formaldehyde or glutaraldehyde fixation, and were encircled by an electron-lucent "halo." The facts indicate that these are perichromatin granules.