Developmental abnormalities in the head region of the talpid3 mutant of the fowl

The inherited abnormality talpid3 in the fowl causes embryonic death on or before the 14th day of incubation, and developmental defects have been observed to appear on the 2nd day. Abnormalities in the head region include a tendency for the eyes to be drawn together in the mid-line, and absence of the upper beak. Rathke’s pouch is abnormal or absent, and in some cases ectopic lenses are produced within the head. Multiple epiphyseal structures are produced from the roof and abnormal ventral evaginations from the floor of the diencephalon. The developmental interrelations of these abnormalities are described, and the possible nature of the basic developmental disturbance isdiscussed. The production of extraocular lens tissue is discussed in the light of information on lens induction in normal embryos.