Question

What are the type of mammalian eggs​

Answer 1

These type of eggs has 2 egg-membranes:

(1) Zona pelucida: It is a transparent membrane like covering & is a primary membrane secreted by the ovum or oocyte.

(2) Corona radiata: It is a layer of follicular cells & these cells are attached to the surface of egg with hyaluronic acid. This is constituted as the secondary membrane, which is secreted by the ovary. These eggs do not have tertiary membrane.

Answer 2

Some embryologists described microlecithal eggs as alecithal eggs or oligolecithal eggs or miolecithal (i.e. little yolk) eggs. The eggs of Amphioxus, marsupials and eutherian mammals are of this type. The mammalian eggs contain so little yolk that they are sometimes called alecithal (without yolk) eggs.