CRANIAL GANGLIA IN AMPHIOXUS. 



121 



is to be found between this and the manner of division described 

 by Hatschek. The typical place of division is about half way 

 between the cord and the dermis. This is not only the mean 

 between two extremes, but it is the place where the rami separate 

 in the great majority of cases. 

 In proportion as the division into 

 rami occurs nearer the cord, a 

 greater number of ganglion cells 

 are found in the rami. The argu- 

 ment of Fu'rb ringer (9, p. 646) 

 that the lateral musculature of 

 Amphioxus corresponds to the 

 mesial portion only of that of 

 craniates, based upon Hatschek's 

 description of the spinal ganglia 

 of Amphioxus outside the mus- 

 cles, is not supported. The 

 greater part of the spinal gan- 

 glion of Amphioyus is situated 

 mesial to the muscles as in 

 craniates. 



It is hoped that the cutaneous 

 and visceral sensory fibers in the 

 dorsal roots may be distin- 

 guished, the position of their 

 respective ganglion cells deter- 

 mined, and the central course 

 of each component traced. The 

 more -general facts regarding 

 these points seem now to be 

 clear. 



The great majority of the 

 fibers of the dorsal roots are fine 

 or medium sized ; a few only are 

 very coarse. The disposition of 



the fibers in the cord can be seen best in horizontal sections pre- 

 pared by the Golgi method. As they enter the cord the fibers 

 spread forward and backward and many pass to or across the 



I 



IK;. 6. Horizontal section showing 

 the spreading of the sensory roots into 

 mesial fine-fibered, lateral coarse fibered 

 bundles and the formation of the dorsal 

 compact bundle. The fibers of the last 

 bundle are strongly varicose. At the 

 upper part of the figure is shown the 

 end-branching of a coarse sensory fiber 

 from the root opposite. 



