50 NERVE COMPONENTS OF BONY FISHES. 



Goronowitsch ('96) describes and figures this tract in 

 Lota under the name of " ascending Trigeminus II " and 

 finds it derived from the lateral line VII (his Trig. II, 

 dorsalis) and from the VIII. It appears to be homologous 

 with the spinal VIII of human anatomy. It is doubtful 

 whether it is completely homologous, if at all, with the 

 spinal VIII of Acipenser, as described by Johnston ('98). 

 The latter tract appears from the description to be made 

 up largely of secondary fibres from the tuberculum 

 acusticum, and not, as here, and as in human anatomy, of 

 direct root fibres. Moreover, Johnston's tract runs back 

 closely joined to the spinal V tract and mesally of it, to 

 terminate in a dorsal nucleus lying mesally of the nucleus 

 funiculi. The tract to which Johnston gives the name 

 spinal VIII is apparently the tract which I term the 

 secondary VIII bundle (Figs. 18 and 19). In Menidia this 

 tract is apparently composed mainly of ascending fibres, 

 though it may contain descending fibres, such as Johnston 

 describes, also. 



The secondary fibres arising in the tuberculum acusti- 

 cum for the most part cross in the commissura accessoria 

 Mauthneri. Some, however, enter a secondary VIII 

 bundle on the same side. The tract to which I have given 

 this name (figs. 18 and 19, Sec. VIII) is composed mainly 

 of uncrossed fibres, but partly, I think, of crossed fibres. 

 It passes into the cerebellum. The other secondary 

 fibres from the tuberculum acusticum, after crossing in 

 the commissura accessoria, enter the tractus bulbo-tectalis 

 (tr. b. /.), and most of them, if not all, pass directly up to 

 to the optic tectum. 



III. — The Communis System. 



Osborn ('88, p. d'^ applies the term fasciculus com- 

 munis to a tract in the amphibian oblongata because of 



