journal of morphology of material i amindebted to dr william m wheeler in an early embryonic stage fig ii when the neural ridgesare just forming and are widely separated there appear in theanterior portion of the neural plate on either side of the median no i optic vesicles in amphibia 191 line and just within the cephalic fold paired depressions awhich are sharply contrasted with the surrounding parts by amuch deeper pigmentation a transverse section through theseareas shows the condition represented in fig iii the hypo blast is a single layer forming the roof of the 2akg87n.jpg from hot show stagedeo asmay View Photo