MORPHOLOtrY OF CKANIAL MUSCLES IN SOME VERTEBRATES. 235 



the Anlageii of the trapezius each branchial myotome forms 

 a transversely broad plate in the branchial septum (Text-hg. 

 9). The part internal to the branchial bar forms the adductor 

 (Text-fig. 15) ; the part external to the bar forms — next the 

 bar, dorsally the arcualis dorsalis^ (Text-fig. 14), and below 

 that the interbranchial, whilst the external edge forms the 

 constrictor snperficialis. 



In Acipenser the lower ends of the branchial myotomes 



Text-fig. 59. 



t«<n^ 



<^^LQA.ar\^. ^*^ 



59. 



iuirW^ 



Rana. larva 11 nmi.. transverse section. 



separate from the cephalic coelom, and in 8^ mm. embryos 

 (Text-fig. 22) grow downwards, except in the fourth branchial 

 segment,- forming the Anlagen of the coraco-branchiales, 

 and also downwards and inwards dorsal to the cephalic coelom, 

 forming the lower parts of the obliqui ventrales. The ventral 

 end of the lower part of obliquus ventralis I becomes attached 



' Employing Filrbringer's terminology (vide p. 2(56). 



^ In the adult forms examined by Yetter the coraco-branehialis 

 IV was absent, and it was not developed in the embryos examined. 

 According to Fiii-bringer it is present. 



