323 



the Trigeminus I, the two tracti epibranchiales anteriores then perhaps 

 being proximal sections, the one of the ophthalmicus facialis and the 

 other of the buccalis facialis. The distal part of the ophthalmicus 

 facialis would then be completely fused with the ramus ophthalmicus, 

 and would not appear as a separate branch. This would better con- 

 form with Alcock's descriptions of Ammocoetes, and also with Für- 

 bringer's descriptions of Petromyzon. For in Fürbringer's descrip- 

 tions it would seem as if the nerve described by him as the "purely 

 sensory" facialis must be largely if not entirely a lateral sensory 

 nerve. Distal to his ganglion z it seems quite certainly the buccalis. 

 Alcock calls it, because of the position of the line of organs it is 

 said to innervate, the ramus ophthalmicus superficialis facialis. It 

 would seem much simpler and more natural because of the course 

 of the nerves to consider the organs as buccalis organs, and not as 

 ophthalmicus superficialis ones. 



A certain amount of confusion in the descriptions and identific- 

 ations of these lateralis nerves is thus here evident, and it is not 

 confined to these nerves alone. Koltzoff, as already stated, calls 

 the ramus ophthalmicus of Ammocoetes a profundus ; and Furbringer 

 shows it, in Petromyzon, lying morphologically ventral to the m. obli- 

 quus superior oculi, as a profundus should. Furbringer says that it 

 enters the orbit ventral to the trochlearis and abducens, which, in so 

 far as its relations to the trochlearis alone are concerned, is also the 

 position of a profundus; but he shows it lying dorsal to all the 

 branches of the oculomotorius, which is the position of an ophthalmicus 

 superficialis, and not of a profundus. I was led, in an earlier work 

 (2, p. 522), to consider it as a profundus, but it is evident that if it 

 contains lateralis fibres, as Koltzoff affirms, it must be a ramus 

 superficialis, and must accordingly lie dorsal to both the trochlearis 

 and the oculomotorius, if the relations of nerves to each other is of 

 any importance; and both v. Kupffer (17, Fig. 46) and Koltzoff 

 {14, p. 340) show it, in Ammocoetes, lying wholly dorsal to the trochle- 

 aris, its relations to the oculomotorius not being evident. 



The weight of evidence thus seems certainly to indicate that there 

 is no true ramus ophthalmicus profundus trigemini in Petromyzon. 

 There may, of course, be, as in Amia, a portio ophthalmici profundi 

 which would supply profundus fibres to the superficialis nerve. 



Turning now to Bdellostoma, there being no trochlearis or oculo- 

 motorius nerves in this fish, there is no anatomical criterion by which 

 to determine whether the ramus ophthalmicus trigemini is a super- 

 ücialis or a profundus ; but it is probable that it is strictly homologous 



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