, Volume 155, Issue 3, pp 399-418

The onset of differentiation in the epiblast of the chick blastoderm (SEM and TEM)

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Chick embryos have been examined by scanning and transmission electron microscopy from the unincubated to the late head process stages (Hamburger and Hamilton stages 1–5). Regional variations in cell structure have been found to develop very shortly after incubation begins and these become more clear cut with further development. In particular, those cells which are destined to invaginate possess fewer microvilli but more globular projections and more vesicles, than the cells which are destined to form the ectodermal covering of the embryo.

We are indebted to Mr. R. F. Moss and Miss D. Bailey for their skilled technical assistance, and we wish to thank Mrs. J. Astafiev for preparing Fig. 34. We are also most grateful for the generous co-operation of Dr. A. Boyde in training one of us in the use of the scanning electron microscope and in making time available on the instrument.