Fig. 4. In situ hybridization and camera lucida drawings of transverse paraffin sections from the cephalic region of D. japonica. (A) The CNS in an intact planarian, which is composed of a mass of nerve cells, the cephalic ganglia (cg) and a pair of ventral nerve cords (nc). I, II and III indicate paraffin section levels. (B) The planarian eye. pc, pigment cell; phc, photoreceptor cell. (C-E) Anteroposterior sequence of transverse paraffin sections, visualized after in situ hybridization with Djsyt. (F-H) Camera lucida drawings of sections in C-E, illustrating the various morphological structures. (I-M) Anteroposterior sequence of transverse paraffin sections, visualized after in situ hybridization with DjPax6A. (N-P) Camera lucida drawings of sections in I-M, illustrating the various morphological structures. The nerve cell marker Djsyt labels all nerve cells, including the photoreceptors, while DjPax6A is expressed only in a subset of nerve cells. No detectable DjPax6A expression is observed in visual cells. Scale bars: 0.05 mm.