A cytological study on the development of the different types of visual cells in the chicken (Gallus domesticus).

The formation of visual cells and their intracellular organelles was studied in the embryonic chicken (Gallus domesticus) between stage 36 and hatching. Cilia formation was observed at stage 30 and by stage 42, outer segment formation from the cilia was evident. The inner segments appeared as buddings at stage 36. By stage 37, the buddings of double cones were observed clearly and such buddings elongated by stage 42. Both the single cones and rods appeared as buddings by stage 38 and elongation of the buddings was seen by stage 42. Oil droplets initially appeared by stage 39 in accessory cones and were observed in other cones by stage 42. Glycogen bodies were demonstrated firstly in rods and accessory cones at stage 43 and their development was completed by stage 45. In essence, all the essential elements of the visual cells were fully developed by hatching.