270 F. U. EDGEWOIM'H. 



from that beliitid^ and its hind end grows backwards below 

 the coraco-liyoideus (Text-figs. 45, 46, 47) to the shoulder- 

 girdle, formiugthecoraco-niandibularis. The portion behind 

 the hyoid bar forms the coi-aco-hyoideus ; in stage 63 it is 

 partially separated into the coraco-hyoideas and abdomino- 

 hyoideus of the adult, ot which the latter is continuous with 

 the truuk muscles behind the shoulder-girdle. 



In Necturus (Miss l^latt) the hypobrauchial spinal muscles 

 are dev^eloped from ventral downgrowths of the third, fourth, 

 and fifth post-otic somites, joined by a few scattered cells 

 from the second somite ; the genio-hyoideus is formed from 

 the third, the steruo-hyoideus from the fourth and fifth. 



In Triton there is a similar development from the third, 

 fourth, and fifth trunk myotomes in 6 A mm. embryos. 



The hypobrauchial spinal muscles of Eana are developed 

 from downgrowths of the first and second trunk myotomes 

 in 6 mm. embryos (Text-fig. 57), which bend round the bran- 

 chial region, forming a longitudinal column which reaches 

 the inferior labial cartilage in 8 mm. embryos. It divides 

 opposite the third branchial bar into genio-hyoid and sterno- 

 hyoid.^ The front end of the former is attached to the 

 inferior labial cartilage (Text-figs. 60, 62), and its hind end to 

 the hypobranchial plate as far back as the antero-posterior level 

 of the third branchial bar. In 12 mm. embryos the internal 

 portion of the genio-hyoid is proliferated from the median edge 

 of the original muscle (Text-fig. 59). At metamorphosis the 

 inferior labial cartilage forms the anterior end of tlie lower 

 jaw, and the muscle so retains its primitive attachments. The 

 front end of the sterno-hyoid becomes attached to the third 

 cerato-branchial, and the muscle extends back to the dia- 

 phragm. 'JVwards metamorphosis the shoulder-girdle is 

 developed and the sterno-hyoid becomes attached to it, and 

 a little later the omo-hyoid is separated from its extei'ual 

 edge. 



In Alytes, Bufo lentiginosus and Pelobates there is no 



' Genio-hypol)ninchiiili.s and diaphriiginatu-lirancliialis iiiediali.s of 

 Schultze. 



