322 



roots each contain spinal and lateral sensory components, but no epi- 

 branchial component. The corresponding ventral roots, that is the 

 motor nerves of the first and second somites, are respectively the 

 oculomotorius and trochlearis. 



The lateral sensory components of the Trigeminus I and Trige- 

 minus II of Ammocoetes are said to be found, in the gnathostome 

 Ichthyopsida, as the rami ophthalmicus superficialis and buccalis 

 facialis, the former doubtless belonging to the Trigeminus I, and the 

 latter to the Trigeminus II, although this is not definitely so stated. 

 These two lateral components, found in Ammocoetes as branches of 

 two wholly separate and independent trigeminal nerves, are assumed 

 by Koltzoff (p. 528) to acquire their origin with the acustico-facialis, 

 in the gnathostome Ichthyopsida, by the atrophy of their primary, 

 segmental connections with the brain, and the development of a 

 secondary connection, by way of the acustico-facialis, and of those two 

 sections of the longitudinal commissure that primarily connect the 

 first and second, and second and third, lateral ganglia. That is, the 

 lateral sensory component of the facialis nerve of the gnathostome 

 Ichthyopsida is assumed to be developed in exactly the same manner 

 that the ramus lineae lateralis vagi of Bdellostoma is definitely said 

 to be developed, by the collecting of the lateral sensory components 

 of certain other segmental nerves. 



From the ganglion of Trigeminus I, in Ammocoetes, a main sen- 

 sory trunk and several smaller sensory branches are said by Koltzoff 

 to arise, the main trunk being called by him the n. ophthalmicus 

 profundus (p. 518). v. Kupffer calls the same nerve simply the ramus 

 ophthalmicus; Fürbringer giving the same name to the correspond- 

 ing nerve in Petromyzon. Neither in Ammocoetes nor in Petromyzon 

 is any branch described, by either of these three authors, as an oph- 

 thalmic lateral sensory nerve; and Alcock (1), who specially studied 

 the lateral sensory organs of Ammocoetes, finds them all innervated 

 by branches either of the facialis, glossopharyngeus or vagus, none 

 whatever being innervated by the trigeminus. 



v. Kupffer shows (16, Fig. 46) the nerve identified by him as the 

 nervus buccalis arising from his ophthalmicus ganglion, but it is con- 

 nected, by a "tractus epibranchialis anterior inferior", with the facialis 

 ganglion. A "tractus epibranchialis anterior superior" connects the 

 facialis and ophthalmicus ganglia. The buccalis is thus here assigned 

 to the Trigeminus I and not to the Trigeminus II, as it is in my 

 interpretation of Koltzoff. Judging from v. Kupffer's figure alone, 

 it would be perhaps more natural to assign it to the facialis than to 



