Fig. 3. Untreated neurosphere in the chick embryo neural tube 24 hours after transplantation (stage 19, HH). (A) GFP epifluorescence is restricted to the lumen of the neural tube. (B) The same embryo as in A, in transversally cut paraffin section. Neurosphere cells remaining in the lumen of the chick embryo neural tube can be seen with no or little attachment to the neural tissue (arrow). Part of the neurosphere fell out of the neural tube lumen during the histological processing (insert).