77 



as well us in dorso-venti'al direction. In WEUiK.RT-prepai'atioiis it 

 often has a greyish eoloui-, which makes me suppose that it consists 

 ol' nieilullai-y as well as unniedullateil fibres. 



Hoiizoiilalis fibre group Lam. cumm, Itcti 



.\llll. Lurl. Fritsch 



■r ■ ,1 '.'•- ' Y 



I r. tsinmo- i ' » , !■ 



Torus /oui^ 



l/iiii fibres ) 

 coiirscfibrc^-^ 



comni.post . 



Cotum. horr:. 

 (pars inf.) 



Xuil. rol. 



Tr. parull.-hulh. Franz 



Fig. 6. Hippoglossoides plalessoides. 

 (Pieparation of Prof. Rothig's Collection, Berlin.) 



ARii^;Ns Kappers in his work on Ganoids (op. cil., p. 475) has 

 e.xpressed the supposition tiiat the middle part of the comniissura 

 posterior partly enters into a connection with the geniculaluiu (i.e. 

 thé iiucl. |)raet-ectalis of (he authors), partly passes over this nucleus, 

 bends backwards and ends in the tegmental region, just under the 

 torus semicircularis. Also in his treatise on the brain of Chimaera 

 (p. 158) and of late in his manual (p. 8J8) he con.siders it as highly 

 probable tiiat this "lateral part" of the commissura posterior originates 

 in the geniculatum (i.e. in the nucl. praetectalis) of the one side 

 and extends caudad on tlie other side (extremely cleai' with Pleuro- 

 nectidae, as he emphasizes). 



Hoi,MGREN calls the relative part of the coramissui'a posterior after 

 Edingkr commissura praetectalis, but is also of opinion that it is 

 "not excluded that praetectalis fibres, that were traced till in the 



