524 JULIA B. PLATT. 
The proximal parts of the nerves of the dorsal and median 
trunk lines now lie some distance below the surface. The 
median parts of the nerves closely underlie the skin, and the 
distal parts run for some distance in the ectoderm. Near the 
base of the nerve of the ventral trunk line several large branches 
are given off, and soon lost in surrounding muscular tissue. 
The first spinal nerve sends its chief branch immediately 
downwards to the ventral wall of the muscle plate, along which 
the nerve runs for a short distance backwards, thus avoiding the 
branchial region; then taking again a vertical direction, it 
meets the second spinal nerve, which passes downwards near 
the anterior wall of the pronephros. The two nerves here 
unite with one another and with the ventral lateral line nerve. 
Beyond the point of union the spinal nerves may still be 
followed forwards for a short distance. The next three spinal 
nerves form the brachial plexus. From each of the spinal 
nerves dorsal and lateral branches arise, which are not repre- 
sented in the reconstruction, and the discussion of which I 
shall postpone. 
Goette (16) tells us that in the “ Unke” the first spinal 
nerve arises from the second trunk segment, and passes over 
the sterno-hyoideus muscle to the genio-hyoideus, and that the 
second and third spinal nerves form the brachial plexus. 
Hence the first spinal nerve in Necturus has apparently no 
homologue in Bombinator. 
Ecker and Wiedersheim (9) speak of the hypoglossus as 
represented in the Amphibia in general by the first spinal 
nerve, which in the frog arises by two roots, an anterior larger 
root, and a posterior smaller root, supplied with a small 
ganglion. The nerve follows a course similar to that of the 
two pre-brachial nerves in Necturus, which therefore probably 
together represent the hypoglossus of other forms. 
I was interested to find that the first two spinal nerves in 
the Ganoidei, according to Stannius (35) and v. Wijhe (loc. 
cit.), have only anterior roots. V. Wijhe regards these nerves 
as lower vagus roots, a supposition which is not supported by 
the development of the nerves, if homologous, in Necturus. 
