546 F. H. EDGEWORTH. 



(text-fig. 38, p. 543) ; in the last named a secondary protru- 

 sible tongue is subsequently formed (text-fig. 39, p, 544), and 

 the genio-glossus becomes its protractor, and also gives rise 

 to a genio-laryngeus. 



The hyo-glossus is inserted into the side of the side of 

 the basihyobranchial in Cheloue (text-fig. 19, p. 525), and 

 Alligator ; it grows forward and ends free in the tongue in 

 Sphenodon (text-fig. 29, p. 532), Agama (text-fig. 31, 

 p. 534), and in early stages of Chamfeleon (text-fig. 34, 

 p. 537). In later stages of Chamteleon the anterior part of 

 the muscle disappears (possibly developing into some of the 

 many intrinsic lingual fibres), wliilst the hinder part forms 

 a muscle passing from the first branchial bar to the ventral 

 end of the ceratohyal cornu.^ In Tropidonotus the hj^o- 

 glossus becomes a retractor of the protrusible tongue, and 

 also gives off a hyo-laryngeus. 



The lingual muscles of Gallus are developed from an 

 Anlage which is homologous with the hyo-glossus of Reptiles 

 (text-figs. 13, 15, pp. 520, 522);^ it at first extends from 

 the first branchial bar to the first basibranchial ; it subse- 

 quently grows forwards and then divides into the cerato- 

 glossus, and hypoglossus rectus and obliquus. This dif- 

 ferentiation of the hyo-glossus is probably related to the 

 fact that the median hyobranchial cartilages in Birds, unlike 

 Reptiles, become jointed. 



In some Birds, e. g. Procellaria,^ though not in Gallus even 

 as a temporary structure, there is also a genioglossus passing 

 from the anterior end of the jaw to the os entoglossum. 



The lingual muscles of the Sauropsida are thus somatic in 

 origin — arising from the anterior element of the ventral 



* The resultant muscle looks a little like the branchioh>-oid of Sphenodon, 

 and the same name, " Ceratoh^^oid," has been given to it, but it is of quite 

 different origin. 



' The Anlage of the lingual muscles of Gallus begins to be formed before 

 the genio-hjoid is quite separated from the sterno-hyoid. 



^ The posterior insertion of this muscle — into the tip of the os ento- 

 glossum and not into the ventral surface of the first basibranchial — shows 

 that it is probably not a persisting genio-hyoid. 



