28 Journal of Comparative Neurology. 



strengthens the beHef. The comparision of sections of Acipen- 

 ser with the figures of Rohon and Sanders of the correspond- 

 ing region of the shark brain indicates that the structure is the 

 same in both. The homology entertained, but rejected, by 

 Strong of Trig. II dot's, with VI I u of Osborn in Cryptobranch- 

 us (my Vllb' in Neduriis^ springing from an island of ground 

 substance upon the dorsal side of the oblongata, is perhaps 

 worthy of being further considered. It was rejected by Strong 

 mainly (apparently) because the conflicting use of " lobus tri- 

 gemini " necessitated other homologies. Were it correct there 

 would persist in reduced state in shark-like ganoids and the 

 larger urodeles the remnant of an elasmobranchian structure 

 {^corpus restifonne ?). Therefore, not to devote more space to 

 it here, it would seem to me that a consideration of the rela- 

 tions of the "lobe" and its nerve root and comparison with 

 ganoids leaves it highly probable that the root from the lobus 

 trigemini in sharks is the homologue ( in part) of Vllb Strong, 

 the lateral line component, and the "lobus trigemini" will 

 prove on investigation to be a modified portion of the acusti- 

 cum system. 



In teleosts the lobus trigemini is but the enlarged cephalic 

 portion of the fasciculus communis system ; fused in the Even- 

 tognathi, unfused in Amhwus ( Nematognathi ?), while in other 

 teleosts examined no lobus trigemini as a special hypertrophy 

 exists. The root from this lobe, the "dorsal geniculate root of 

 the Vth " is the homologue of Vllaa in Amphibia and is pres- 

 ent whether a lobus trigemini as such exists or not. This is 

 not saying, however, that they are in each case exactly equiva- 

 lent. 



In view of the foregoing statements the following may give 

 help on some of the points and problems raised by Strong. 

 In the first place, the nerve of Goronowitsch from the "lobus 

 trigemini " of Acipenser is not the homologue of the geniculate 

 V of teleosts which is the representative of his dorsal root of 

 the seventh (Frd.) from the fasciculus communis (lobus vagi). 

 The recognition of Tlld. as a lateral line root clears up the dif- 

 ficulties occasioned by its distribution to the ophthalmicus su- 



