336 G. E. COGHILL 



Figs. 66 to 70 Early swimming stage (No. 496, sections 1-6-19 to 23). X 500. 

 Five successive serial transverse sections through the entrance of the root of 

 the vagus nerve into the brain. Figure 66 is the most rostral in position. In 

 this figure the fasciculus solitarius {Fas. Sol.) can be recognized between the 

 descending trigeminal tract (Tr.Des.V) ventrally and the ascending fibers of the 

 spinal Rohon-Beard cells dorsally (DT). The visceral sensory root of the nerve 

 (R.Vis.X) enters in figures 67 and 68 and the somatic sensory root {R.G.Jug.) en- 

 ters in figure 69 ; the visceral sensory root entering more dorsally. Figure 70 shows 

 fasciculus solitarius fibers caudally of the entrance in a relation like that in 

 figure 66, which is on the rostral side of the root. The somatic motor column is 

 shown in 67, 69 and 70 {VT). The visceral motor nucleus appears in all the 

 figures of this set, and lying between it and the external limiting membrane is a 

 tract {Tr.S) which can not be described in detail in this paper. It is probably 

 a bulbo-spinal tract. The figures of this set should be compared with figure 6. 



