Study of the intermediate stages of Coturnix coturnix japonica reveals the following events:-
1.The intertrabecular bar extends in a dorsal direction to form firstly the nasal septum then later the interorbital one.
2.The hypophyseal incisura converts into a hypophyseal fenestra.
3.The anterior orbital cartilage begins to disappear completely at the end of these stages.
4.The paranasal cartilage has an isolated center of chondrification.
5.Also the parietotectal cartilage emerges from a separate center of chondrification apart from the nasal septum.
6.Both of conchae atrioturbinal and maxilloturbinal cartilages have the same center of chondrifiction which is the venteral surface of the parietotectal cartilage.
7.Paries lateralis nasi originates from the union of the paranasal cartilage and the parietotectal cartilage.
8.The lateral wall of the nasal capsule in the posterior region ( planum antorbitale) is developed.
9.The metotic cartilage has two centers of chondrification; lateral and medial one.
10.Fusion of the cochlear and canalicular portions of the auditory capsule takes place.
11.Both of fenestra ovalis and foramen perilymphaticum are developed as reabsorption in pre-existence cartilage.
12.The promontorium is formed at the end of these stages.
13.The posterior edge of the occipital arch fails to fuse in the mid –line to form the tectum synoticum at the end of the intermediate stages .
|
