The technique of marking the unincubated duck blastoderm with fine particles of Chinese ink leads to the following conclusions:

  1. there exist superficial morphogenetic movements during the first few hours of incubation;

  2. surface material rolls round the posterior, lateral, and anterior margins;

  3. there is a direct continuity between extra-embryonic and embryonic endoblast.

The endoblastic layer forms therefore by surface material rolling round the posterior, lateral, and anterior margins.

You do not currently have access to this content.