234 NERVE COMPONENTS OF BONY FISHES. 



fasciculus longitudinalis dorsalis, though this conjecture 

 could not be verified. We already know that the oculo- 

 motor nuclei are placed in relation with each other and 

 several sensory centres through the mediation of this 

 tract. Cf. the diagram of Bonnier, '95. And this would 

 suggest that possibly we have here a sensory mechanism 

 analogous with the muscle spindles. The structure, how- 

 ever, does hot conform very well, and we are told, more- 

 over, that spindles do not occur in the eye-muscles 

 (Batten, '97, p. 176). The comparison is rendered more 

 difficult by Sherrington's experimental proof (fide Huber 

 and DeWitt, '98) that the spindle nerves are derived 

 from the dorsal spinal roots, while the small oculomotor 

 fibres quite certainly come out with the other and 

 undoubted motor fibres of the eye-muscle nerves. The 

 whole question demands further study. 



In order to facilitate comparison of the eye-muscle 

 nerves of Menidia with Allis' account and the elaborate 

 phylogenetic scheme which he has elaborated ('97), I 

 have prepared the diagram, Fig. 13, which should be 

 compared with Allis' Fig. 12, Plate XXII. 



The courses of the trochlearis and abducens are in 

 Menidia essentially as in Amia; but the relations of the 

 oculomotorius are in several respects different. This 

 nerve emerges from the cranium some distance ventrally 

 of the Gasserian ganglion and is crossed externally while 

 still within the foramen by the truncus infra-orbitalis. 

 Its foramen is far caudad of that of the optic nerve and at 

 the level of the latter all of the branches of the third 

 nerve except that for the m. rectus superior lie ventrally 

 of the chiasma. In all of Allis' figures the ophthalmic 

 nerves (superficial and deep) arise from a common stem 

 which lies ventrally of the III nerve, and he states in the 

 text that in Amia the latter nerve "pierces the lining 

 membrane of the cranial cavity opposite and above the 



