Fig. 2. Effect of FGF2 on neural crest cell morphology. Phase contrast photomicrographs illustrate that after 5 days (A-C) neural crest cultures grown in the absence of FGF2 have flattened considerably (A) whereas cells in 1 ng/ml FGF2 retain a more compact cell shape (B) and those in the presence of 10 ng/ml FGF2 have begun to form small nodules resembling cartilage (C, arrowheads). Following 10 days in culture (D-F), cells in control cultures have flattened even further with intercellular spaces appearing (D), whereas in 1 ng/ml FGF2, a concentration that enhances proliferation, there is an increase in cell density (E), while the nodules formed in 10 ng/ml FGF2 have increased markedly in size compared with 5 day cultures (F, arrowheads indicate perimeter of nodule). Scale bars: 100 µm.