In this one lucky shot are illustrated all of the fates that befall the products of animal meiosis in a typical animal.  The animal in question is a nemertean worm, Cerebratulus, which, although perhaps unfamiliar to the man in the street, happens to exemplify the typical animal strategy for gamete creation and fusion.  It makes small swimming sperm and large well-provisioned eggs, which are shed into the sea, where they meet, fuse, and initiate embryogenesis as a zygote.

The products of male meiosis are all equivalent.  Of course, some sperm make it and some – most – don’t.  In the center of this egg is the nucleus of the single sperm that fused with the egg, probably the first one that encountered it, and nearby is the sperm aster (the radial array of microtubules at the very center is created around the sperm’s centrosome).  And just outside the egg, at the very top of the picture, the bright blue wedge is a sperm that bound but couldn’t fuse; most animal eggs have some means to prevent more than one sperm from entering, and this one came too late.

In female meiosis the products are not all equivalent.  The cell that was fertilized here was not yet actually an egg, per se, but an oocyte: the fully-grown gamete-forming cell, which has yet to complete meiosis.  In fact it will never be an egg, strictly speaking, because Cerebratulus is like most animals in that its oocytes wait until they are fertilized before they complete meiosis.  A haploid female gamete never really exists in such a case.

The oocyte has a replicated, diploid genome; this means four copies of every chromosome.  To make an egg – a haploid gamete – it needs to get rid of three of those.  Oocyte maturation consists of two highly-asymmetric cell divisions that create polar bodies – tiny cell-lets only big enough to hold the cast-off chromosome complements.  In this picture, one polar body has already formed; it’s at the top, just outside the egg, and contains a diploid nucleus and so little cytoplasm that it has no future.

The other polar body is about to emerge.  The Cerebratulus oocyte creates a glorious meiotic spindle with an enormous, extensive aster on the cytoplasmic end, and the other end plastered right against the cell surface.  At the time this cell was preserved, it had just commenced anaphase, so the fates of all the chromosomes were settled.

Incidentally, this glorious spindle is the last work of the maternal centrosomes.  They will be discarded into polar bodies or destroyed.  The sperm’s single centrosome is the founder for all of the centrosomes in the new organism.