Paired pineals in the developing quail (Coturnix coturnix japonica) embryos.

Paired pineals were observed as an anomaly in embryonic quail brains between 7 and 9 days of incubation. The size of each pineal was almost the same as that of the normal pineal and it was located slightly lateral of the midline. Histological examination of these paired pineals revealed that both had similar cytological features in comparison with the normal pineal of the same developmental stage. No abnormal features were detected in brains and eyes of the embryos with paired pineals. Since the presumptive pineal rudiments are considered to exist in the neural folds and to fuse in the midline during the formation of the neural tube, the paired pineals may be interpreted as a result of incomplete fusion of the pineal anlagen. This report describes for the first time the symmetrical occurrence of pineal glands in the developing avian brain.