FIGURE 2.3 (a) Sperm nearing the egg Of the millions of sperm that started out together, only a few ever get near the egg. The egg is the largest human cell (the only one visible to the naked eye), but sperm are among the smallest. (b) Sperm penetrating the egg This sperm is whipping its tail around furiously to drill itself through the outer covering of the egg.
LENART NILSON/SCANPIX
LENART NILSON/SCANPIX
LENART NILSON/SCANPIX