Fig. 2 Confocal laser scanning microscope images of double-stained specimens of Flagellophora cf. apelti. Double staining of alpha-tubulin IR (green) and FMRFamide IR (red) elements. a–c Sagittal optical sections through the anterior end of the body of the same specimen. Dorsal side is on the right. Note the median broom organ, passing ventrally of the statocyst, the unstained area on the right that presumably contains the brain neuropile and an aggregation of FMRFamide IR brain cells around it, mostly anterior to it. The apparent FMRF-amide staining of the epidermis is an artefact resulting from the high-intensity scans necessary due to the comparative weakness of the red fluorescence to that of alpha-tubulin; it is missing in Fig. 2d. d Anterior