No. I.] THE CRANIAL NERVES OF AMPHIBIA. 203 



concomitantly become more restricted to certain regions and 

 would, not improbably, undergo further specializations. Ac- 

 cording to this view, the cutaneous sense organs would have 

 had at first a more general innervation, and only later would 

 their nerve supply proceed from only one or two nerves. 



Another change which seems to have taken place, similar in 

 character to the above but affecting a different structure, is the 

 assumption by several nerves of the supply to the gills (and 

 other visceral structures T) and concomitantly the creation in 

 the medulla of a special center for this nerve supply (lobus vagi). 



Hatschek points out the superficial position of the ganglia in 

 Amphioxus as compared with the spinal ganglia in vertebrates. 

 If the above homologies (p. 200), with Kupffer's results, be 

 correct, it is precisely the branchio-visceral ganglia of the 

 VII— IX— X (epibranchial ganglia), and the special cutaneous 

 ganglia (lateral line ganglia and ganglia of nerves to end buds 

 also, perhaps) which arise from special epiblastic thickenings as 

 opposed to those ganglia derived from the neural crest, and it 

 is precisely these ganglia which belong to the cranial nerves 

 with long trunk branches, in other words, those which have 

 taken the place of certain portions of the spinal nerves. The 

 ganglia, then, of the cranial nerves, arising in connection with 

 epiblastic thickenings, are the ganglia which the spinal nerves 

 do not possess, having probably lost them. This would explain 

 this difference in the mode of origin of cranial and spinal 

 ganglia. 



The fusions described, in connection with the Trigeminus, 

 by Beard and Kupffer possibly belong to the lateral line gan- 

 glion which lies over the Gasserian ganglion proper, possibly, 

 also, to nerves to end buds. 



Of course the presence of the lateral motor roots in cranial 

 nerves constitutes a difference of another character from the 

 above. This and the correlated problem of the sympathetic do 

 not fall within the scope of the present discussion. 



There are several anatomical peculiarities which afford further 

 support to Hatschek's comparison, as amended above. These 

 are the remarkable parallelisms existing between these three 

 systems of cutaneous nerves. I have called attention to the 



