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Summary Stage Literature (155) Attributions Wiki

Name: NF stage 21

XAO ID: 1000037

Definition: "Nieuwkoop and Faber stage 21, corresponding to an embryo of age 22 hr 30 min at 22-24 Celsius and having the following external morphological criteria: Suture of neural tube completely closed. Delimitation of frontal field by pigment lines. Primary eye vesicles showing through in the form of two separate, obliquely placed oval spots; beginning of protrusion of eyes. Lateral outline of embryo just becoming concave, ventral outline flat. Length: 1.9 - 2.0 mm."

Preceded By: NF stage 20 Succeeded By: NF stage 22