The structure formed as a result of the fusion of gametes in a species is known as:

The fertilized egg divides by the process of

Who first observed the process of fertilization in sea urchins?

$A$: Fertilizins are glycoproteins present on the surface of the egg membrane.
$R$: They help in the agglutination reaction by interacting with anti-fertilizins on the sperm surface to facilitate fertilization.

Cleavage was first observed by

The embryo at the $16$-celled stage is called: