Fig. 22. High power TEM of part of a pronuclear nucleolus in a stage 1b embryo in vitro, 17 hours post-insemination (original magnification x51,710). The nucleolus is dense, compact and homogenous, and composed of fine fibrils. The chromatin is highly dispersed and finely granular.
(From: Sathananthan and Trounson, 1985. Reproduced with permission of the publisher, John Wiley & Sons )