6o 'Journal of Comparative Neurology and Psychology. 



of the com. posterior "in the mesal denser part of the nidulus 

 corticalis," which agrees with the situation of the nucleus lenti- 

 formis which laterally fuses with the nucleus corticalis. Gold- 

 stein saw the same tract as Herrick describes it, and as I saw 

 it running along with the com. horizontalis, as mentioned above, 

 but he regards the com. horizontalis as a part of it, viz., as a cere- 

 bellar commissure, and he saw its frontal curve passing upward 

 into the tectum, which I cannot confirm. My results are the same 

 as those of C. L. Herrick, with the qualification that I doubt 

 whether the tr. mesencephalo-cerebellaris superior afterward 

 decussates in the cerebellum. If some of its fibers cross there, it 

 is surely only a small part. Johnston probably saw the same 

 connection in Acipenser and gave it the name of tr. tecto-cere- 

 bellaris, as he, too, saw its fibers going upward into the anterior 

 part of the tectum. He does not describe any decussation of its 

 fibers. 



The fasciculus longitudinalis lateralis runs parallel with, and 

 lateral to, the bundle last described, arising from the nucleus 

 lateralis mesencephali, which is situated in the colliculus, or torus 

 semicircularis, where its fibers are assembled from a large area 

 (Figs, xlviii to li, Plate HI). The tract is very distinct in Gadus 

 and more easily traced than in any of the other fishes examined. 

 It runs backward into the oblongata as a compact medullated 

 bundle and ends after decussation in the acoustic lobes, forming 

 in this region the greater part of the dorsal arcuate fibers (Fig. 

 xciv, Plate VI). The tract must be regarded as a secondary 

 acoustic tract and has been described in higher vertebrates also 

 as a connection between the acoustic center and the corpus 

 quadrigeminum posterius, of which, as I pointed out above, the 

 colliculus must be regarded as the homologue, or rather as a 

 prostadium, m the teleosts. 



Johnston, who apparently described the same tract in Aci- 

 penser, saw the greater part of its fibers ending in the tectum, 

 which agrees with the fact that the colliculus must be regarded as 

 derived from the deeper layer of the tectum and with the ending 

 in the colliculus of a part of the lemniscus fibers and with the fact 

 that in the ganoids the colliculus is far less strongly developed 

 than in the bony fishes [cf. the account of the selachians in the 

 second part of this chapter). The name which Johnston gave 

 to his secondary frontal acoustic tract is tr. bulbo-tectalis, which 



