MOTOR NUCLEI IN PHYLOGENY 417 



the homologue of the cucularis muscle of higher forms must be 

 looked for not in the piscian trapezius alone, but in this muscle 

 plus certain closely associated and synergic effectors derived 

 from the somatic musculature and innervated by spinal nerves. 

 For these reasons the elements referred to were designated vis- 

 ceral and somatic components respectively of the trapezius 

 complex (v. 10, p. 546). 



If the above conception of the phylogeny of the sauropsidan 

 cucularis be correct it may be expected that, in view of the 

 absence of a bony operculum in amphibians, both the somatic 

 and the visceral components of the trapezius complex will be 

 retained in these forms. Further, in contrast to sharks, the 

 functional differentiation of the somatic components from the 

 general trunk musculature as well as the specialization of the 

 visceral components should be more extensive especially in 

 anurans, while in the more primitive urodeles some indication 

 of a saurospidan prostadium may be looked for. It will be of 

 interest therefore to consider briefly certain anatomical facts 

 bearing upon these questions. 



In Rana (Gaupp, I.e.) the so-called visceral components of the 

 trapezius complex may be recognized without difficulty in the 

 mm. cucularis and interscapularis. On the other hand, the 

 levator musculature derived from the trunk segments has under- 

 gone such extensive differentiation in anurans that it is difficult 

 if not impossible to select any one of the muscles associated 

 in this function as the sole representative of the somatic com- 

 ponent of the trapezius complex of higher forms. Dorsally the 

 m. rhomboideus anterior, innervated from the III spinal seg- 

 ment, acts synergically with the m. cucularis and was even mis- 

 named m. cucularis by Ecker on account of its relations (v. 

 Gaupp, 25 p. 103). Ventrally the m. levator scapulae inferior, 

 innervated from the II spinal segment, is also closely associated 

 with the m. cucularis, with which its action is synergic. For- 

 tunately, however, it is of no moment in the present connection 

 to attempt to decide which of the many possible muscles may 

 represent the somatic component of the trapezius complex in 

 these forms; it is sufficient merely to indicate that in the ab- 



