ORIGIN AND STRUCTURE OF THE HEAD 



141 



The anterior ones of the post-branchial myotomes, from 

 the ninth (seventh post-otic) onwards (Neal, 1897, p. 444, 

 KOLTZOFF, 1902, p. 304), produce myotomic buds which 

 grow out behind and under the gill-slits and produce the 



Fig. 29. Head of Fetromyzon fluviatilis, dissected, 

 after Goodrich, 1909, p. 40. 

 /, It, eye-muscles derived from the two 

 prc-otic somites. 

 Ill: IV. V, etc. myotomes. 

 occ. a. occipital arch. 



hypobranchial musculature which afterwards exhibits a 

 secondary segmentation corresponding to the situation of 

 the gill-slits. It is innervated by ventral roots of the myo- 



