Carnegie Stage 1c

Fig. 5. TEM of a late stage 1c embryo in vitro showing two pronuclei in the central cytoplasm with a interpronuclear zone, 24 hours post-insemination. Cytoplasmic organelles are abundant around the pronuclei particularly dense mitochondria (M). The lower paternal pronucleus shows a protuberance (arrowhead). The envelope of the maternal pronucleus above is beginning to dismantle. This occurs just before syngamy. Both pronuclei have dense, compact nucleoli and a few intrapronuclear annulate lamellae (IAL).

GC, Golgi complex; S, vesicular smooth endoplasmic reticulum.

(From: Sathananthan, 1984. Reproduced with permission of the publisher, Churchill Livingstone.)