STAGE 31 Age 1 d., 13 ½ h.; length 4.2-4.8 mm.

Ext.Crit.: Mushroom -shaped epiphyseal evagination; hypophseal cell plate reacign to caudal border of chiasmatic reidge, but still connected with ectoderm. Nerves beginning to grow out from gangl.VII; appearance of gangl.VIII Neural crest of spinal cord entirely withdrawn from neural tube; *thin layer of nerve fibres extending over 70% of length of spinal cord*.Nasal pit indicated. Central portion of retinal layer concave.

*Segregation of 2^nd branchial portin of mesectoderm * .* 22-23- post otic somites* appearance of "Urwirbelfortsatze" on ventral sides of anterior myotomes.* 1^st pair of aortic arches completed, and beginning of paired dorsal aorta formed *; pronephric sinus formed. 1^st nephrostome funnel completed.