In the egg of bird, shell and shell membranes are
Permeable to ${O_2}$ and $C{O_2}$
Permeable to water only
Permeable to air only
Non-permeable
$FSH$ and $LH$ is
The phenomenon of fertilization was first perceived by
The rolling of endodermal and mesodermal cells from the surface of embryo into its interior is called
Egg which contains very little amount of yolk are called as
Middle gastrula is characterised by