STAGE 26. Age 1 d., 5 ½ h.; length 3.0-3.3 mm.

Ext. Crit.: *Ear vesicle protruding*. *Pronephros distinctly visible*; Myotomes showing through for the first time. *Fin somewhat broadened at dorso-caudal end of body*. Beginning of spontaneous movements.

Int. Crit.:  First indications of olfactory lobe formation in antero-lateral portion of telencephalic wall; beginning of evagination of pineal body. In posterior 1/5, spinal cord not yet completed and central canal still unconstricted. *Lateral wall of primary eye vesicle showing local protrusions on inner surface*.
*Head somite 1 disintegrated; 17 somites segregated*. *Wolffian duct anlage extended to level of trunk somite 3*.
*First contact of ectoderm and entoderm in 2^nd visceral pouch (formation of hyoid arch)*. Postanal gut indicated.