404 Journal of Comparative "Neurology. 



the most satisfactory criteria of these homologies will be the 

 relations of the ophthalmic nerves to the eye muscles and their 

 nerves and to the other orbital structures, as AUis has employed 

 them in his Amia paper. The composition of the nerves prox- 

 imally cannot be used in any of the higher vertebrates where 

 the profundus has fused with the trigeminus, for both the deep 

 and the superficial branches of the trigeminus in these forms 

 are primarily general cutaneous nerves, and both apparently 

 may carry out also communis fibers from the facial ganglion. 



Accordingly, the nerves of the orbit of Ameiurus have 

 been plotted on cross-section paper and these relations carefully 

 noted, as well as the exact nature of the termini of such of 

 these nerves as reach the skin. This is one step in a detailed 

 examination of the cranial nerves of American and African 

 siluroids now in progress in this laboratory, and the present 

 account will be confined to the peripheral courses of the orbital 

 nerves after their separation from the ganglionic complex. This 

 complex and its roots have, however, been as fully worked out 

 as our present material will permit and the composition of the 

 rami now under discussion can be stated, if not with absolute 

 certainty, at least with a very high degree of probability. 



As indicated above, there are two ophthalmic nerves in 

 Ameiurus. The first, or more superficial one, is undoubtedly 

 the r. ophthalmicus superficialis facialis. Its fibers separate from 

 the trigemino-facial ganglionic complex earlier than do those of 

 the other ophthalmic nerve and can be traced back into the 

 dorsal lateralis root of the facialis. It receives no other fibers 

 than these and distributes peripherrally to the organs of the 

 supra orbital lateral line and to the pit organs of the top of the 

 head and snout. Its course for its entire length is essentially 

 Hke that of the corresponding nerve in the other bony fishes. 



The other ophthalmic nerve, which, as we shall see, is the 

 ramus ophthalmicus superficialis trigemini, arises from the gan- 

 gUonic complex some distance cephalad of the nerve last de- 

 scribed. It receives general cutaneous and communis fibers in 

 approximately equal numbers. The former come from the 

 sensory trigeminus root, a root which, together with the motor 



