

455 



Tin- formation of tin- ner\r lihrill:. 



as has already been atatad and as will l>e furth.-r -\i.' 



connection. According t.. tin* view of most observers, the nerve- 

 lihrilla-- the future a\i> cylinders are formed as processes of gang- 



lionic ci-lls ..t' tin- spinal cord, the free ends of which grow nut tn.m 

 the Mil-face of the latter until they re Lfans 



(Km BftLum, Hi-. s.\.,i i 



mjf 



pk - 



fig. 260. - Cross section of a Lizard embryo with completely closed intestinal canal, after 



1:111 . 



he, Posterior [dorsal], re, anterior commissure of the spinal cord; vte, ventral nenre-root; 



V, nerve- fibril las ; spt, spinal ganglion; iwp 1 , muscle-plate, muscle-producing layer; 



7 , outer layer of the imucle-plate ; mp*, transition from the outer to the muscle- 



are :i\vn especially fur the . level.. i-m.-n: 

 higher Vrrt'lr 



Accordini: to tl;e opinion of I'OIIUN and VAN WI.IUK. on 



contrary, the nerve-tihrilhe ari->e in Mtu. as j,r. '.itlerentia' 



from the protoplasm of the cord- of c.-ll> l.y n Nvhich nn: 



Moment and spinal . ord are already un -d to 



seek out the terminal onran. since there i-xi>t- I protopluMiiie 

 union with it. They arise in a in. ailar to that in which 

 the nmsrle-tn>rill:v do frnn the plasii; 



