Which of the following is $NOT$ true for gastrulation?

The zygote passes through several developmental stages until implantation. Describe each stage briefly with suitable diagrams.

After gastrulation,the roof of the archenteron is formed by:

Women who consumed the drug thalidomide for relief from vomiting during the early months of pregnancy gave birth to children with:

After one month of pregnancy,the embryo's $A$ is formed. By the end of the $B$ month of pregnancy,the foetus develops limbs and digits. By the end of $C$,most of the major organ systems are formed,for example,the limbs and external genital organs are well-developed. By the end of $D$,the body is covered with fine hair,eyelids separate,and eyelashes are formed. Here $A$ and $D$ refer to:

If you remove all cells that form the endoderm from an egg in the gastrula stage,the new organism will lack which of the following?