258 



F. n. ED<;r]W()RTn. 



genenxl development of tlie myotomes takes place from belore 

 backwards, tlie separation (jf the upper ends of the branchial 

 myotomes, their backward g'rowth, and fusion to form a 

 trapezius, in Scyllium, Clirysemys, GaNus, and Lepus, take 

 place from behind forwards — the process beginning in the 

 last branchial myotome. 



Adductors of the branchial bars are formed in Scyllium 

 and in certain segments of some Teleostomi, on the inner 



Text-fi«. 71. 



on^ colU. 



La(;ertii. eiuljvyo 12 mm., transverse section. 



side of the branchial bars. The observations of Balfour^ 

 showed that the primar}^ situation of the nniscles is one 

 external to the bars, so that the non-development of adduc- 

 tors in Amphibiii, Ceratodus, and Polypterus would appear to 

 represent a ])riinitive condition. 



It may be added that the adductors of the branchial bars 

 are not serially liomologous with the adductor maudibuhe, 

 which is formed external to the mandibular arch. 

 ' ' Coniparative Emliry()lo<4'y." vol. ii. p. ITl. 



