On the Development of the Hyobranchial Skeleton of the Midwife-Toad (Alytes obstetricans).



In the hyobranchial skeleton of the early larva of Alytes there is an anterior copula which subsequently disappears and forms no part of the adult hyoid.

The posterior copula extends backward to the laryngeal sinus, and thus completely separates the two hypobranchial plates. It persists as the central part of the body of the hyoid.

The postero-lateral process of the adult hyoid cannot be identified with the base of the first ceratobranchial as it can in Pelodytes, but both the antero-lateral and postero-lateral processes are new formations, as in Rana.

The branchial bars or ceratobranchials of the larva form no part of the adult hyoid, but are entirely resorbed.

The thyrohyal is developed from that part of the hypobranchial cartilage of the larva which constitutes the inner boundary of the thyroid foramen.