248 F. H. EDaii WORTH. 



Bufo lentig'inosus, and PelobateSj ill ]avv» of about the 

 same length. In Rana it disappears late in metamorphosis. 

 'J^he trapezius (capiti-scapnlaris, of Furbringer ; cnciillaris, 

 of Ecker and Gaupp) is formed early in metamorphosis from 

 cells proliferated from the outer surface of the ft)urth levator 

 (Text-fig. ()1). 



In 6 mm. embryos of Chrysemys inarginata there are 

 four branchial myotomes; in 8 mm. embryos (Text-figs. ()G-69) 

 the middle portion of the first is very slender and that of the 

 second has disappeared, and the middle and lower portions 

 of the third and fourth have disappeared ; the upper end of 

 the fourth has extended back a little in the neck, tlie upper 

 end of the third has extended back to that of the fourth, the 

 upper end of the second is a separate structure, and the upper 

 end of the first is still connected with the rest of the myotome. 

 In 12 mm. embryos the dorsal ends of the first and second 

 have each grown backwards into the next segment, and there 

 is thus formed a long column of cells which has grown still 

 further backwards into the neck, forming a trapezius — the 

 capiti-plastralis of Fiirbringer; the middle portion of the 

 first and the lower end of the second myotomes^ have dis- 

 appeared, whilst the lower end of the first forms tlic inter- 

 arcualis ventralis I, which, extending from the fii'st branchial 

 bar to Meckel's cartilage, is the branchio-mandibularis. 



In Lacerta agilis the dorsal edge of the juiinitive 

 trapezius extends upwards outside the trunk myotonies of the 

 neck (Text-figs. 70, 71), and in 20 mm. embryos it has divided 

 into dorsal and ventral portions, the capiti-dorso-clavicularis 

 and capiti-cleido-episternalis of Furbringer. The former is 

 innervated solely by spinal nerves, the latter by the acCes- 

 sorius vagi. Furbringer concluded from this innervation 

 that the ca{)iti-dorso-c]avicularis is a new formation, and that 



' The curious persistence for ;i. time of the lower end of the seeoiul 

 liraiicliial myotome, after disappearance of the middle portion of the 

 luyotome, is in favcmr of the idea (loc.cit.) tliat ancestors of the 

 Sauropsida may liave possessed an interarcualis ventralis II. passing,' 

 from the second to the first Ijrancliial Ijar. 



