The phenomenon of fertilization was first perceived by

Cleavage is a unique form of mitotic cell division in which

The permeability of the human placenta to macro-molecules is evidenced by the presence of following in foetal blood

After implantation, finger-like projections on the trophoblast are called $…A….$ which are surrounded by  $…B..$ and maternal blood. Here $A$ and $B$ refers to

In which animal the testes are abdominal during embryonic stages but migrate to scrotum just before birth where they remain throughout life