546 DAVIDSON BLACK 
in question is considerably greater in Lophius, where the trape- 
zius is present, than in Gadus, where the representative of this 
muscle is innervated by spinal nerves. The motor vagus nucleus 
in both Silurus and Ameiurus is continuous with that of the 
glossopharyngeus, but the line of demarcation between these 
two nuclei has been determined as the level beyond which no 
motor IX fibers can be traced. The total length of the motor 
vagus nucleus determined in this way is approximately equal in 
the two forms and is evidently greater than that of the isolated 
nucleus in Lophius. 
From this it would appear that the caudal end of the vagus 
nucleus in Silurus, Ameiurus, and Lophius, represents a true 
nucleus accessorius, homologous in all respects with that of 
selachians, while in Gadus this nucleus is wanting. 
In view of the fact that the trapezius muscle of higher forms is 
habitually innervated from two distinct sources, it seems highly 
significant that a muscle is present in certain teleosts (e.g., 
Gadus) which by reason of its connection with the cranium and 
shoulder girdle must functionate as a trapezius, even though its 
innervation by spinal nerves must preclude its homology with 
the trapezius of selachians. 
In the case of Gadus Herrick (35, p. 298) notes: ‘‘The muscle 
running from the cranium to the pectoral girdle in Gadus is 
innervated from the spinals and not from the vagus. It is 
therefore, merely a detached portion of the general dorsal mus- 
culature.”’ If, however, this muscle in Gadus be considered in 
comparison with conditions obtaining in higher instead of lower 
forms, the peculiarity of its innervation would not exclude it 
entirely from homology with the cucularis. 
Evidence that the cucularis of higher forms has been derived 
in phylogeny from two different sources is furnished by its double 
nerve supply. As the presence of definite somatic components 
inextricably mixed within this muscle complex seems limited to 
higher vertebrates (Sauropsida and Mammalia), this pecu- 
liar condition of fusion must be a comparatively recent phylo- 
genetic acquisition. If this be so, both components may be 
