ON THE SPINAL NERVES OP AMPHIOXUS. 
91 
are to he seeuy though the whole length and very finest branches 
of the posterior nerves are preserved. 
By treating with nitric acid and clarifying by oil of cloves, and 
subsequently removing one half of the body so as to expose the 
spinal cord in situ, the origin and distribution of the posterior 
nerves is very clearly exhibited. But I have failed to detect 
any trace of the anterior nerve-roots. Horizontal section, which 
ought also to bring them clearly into view, failed to show me 
anything wdiich I could interpret as such. I agree with Schneider 
that a process of each muscle-plate is prolonged up to the anterior 
border of the spinal cord, but I can find no trace of a connection 
between it and the cord. 
Schneider has represented a transverse section in which the 
anterior nerves are figured. I am very familiar with an appear- 
ance in section such as that represented in his figure, but I 
satisfied myself when I previously studied the nerves in Amphi- 
oxus, that the body supposed to be a nerve by Schneider was 
nothing else than part of the intermuscular septum, and after 
re-examining my sections I see no reason to alter my view. 
A very satisfactory proof that the ventral nerves do not exist 
would be found, if it could be established that the dorsal nerves 
contained both motor and sensory fibres. So far I have not 
succeeded in proving this ; I have not, however, had fresh 
specimens to assist me in the investigation. Langerhans,^ whose 
careful observations appear to me to have been undervalued by 
Schneider, figures a branch distributed to the muscles, which 
passes off from the dorsal roots. Till the inaccuracy of this 
observation is demonstrated, the balance of evidence appears to 
me to be opposed to Schneider’s view. 
^ ‘ Archiv f. Mikros. Anatomie/ vol. xii. 
