Kappers, Tehostean and Selachian Brain. 53 



anteriores of the teleosts with the paUium of the selachians. The 

 reasons which Haller gives for his opinion do not agree with 

 my observations. For his hypothesis is founded on the constitu- 

 tion of the tr. strio-thalamicus itself, described by him as, "die 

 aus dem jederseitiger Vorderhirn aus je zwei Theile besteht, aus 

 einem Thalamus Theil und einem caudalen Theil, der wieder in 

 eine gekreuzte und eine ungekreuzte Portion zerfallt." Moreover, 

 he saw in Scyllium in the mantle-bundle also a decussated and an 

 undecussated part. In both the teleost and the selachian which 

 he examined he saw the decussation mentioned in the same 

 commissure, and by reason of this fact he believes that in the 

 striatum of the bony fishes there are pallial parts which, as I have 

 already said, is not in conformity with my observations, although 

 I am quite ready to allow that the final results of our investigations 

 in this matter agree in the chief point. 



Chapter III. 



THE MID-BRAIN, MESENCEPHALON. 



I. The Mid-braui of the Teleosts. 



From the description of the 'tween-bram it has already appeared 

 that the dorsal wall of the mid-brain is much larger than the dorsal 

 wall of the 'tween-brain and that a part of the latter is over- 

 arched by the tectum opticum. For the dorsal part of the 'tween- 

 brain does not extend farther caudad than the commissura 

 posterior, while its ventral part with the lobi inferiores extends 

 under the base of the mid-brain. Under these circumstances it 

 is, of course, difficult to mark a sharp boundary line between the 

 'tween-brain and the mid-brain, which extends from the commis- 

 sura posterior above and in front to the posterior irtsertion of the 

 lobi inferiores ventro-laterally. 



This is why I found it difficult to omit the description of some 

 systems belonging to the mid-brain in the second chapter. I 

 there treated particularly and in detail the direct and indirect optic 

 connections of the tectum; accordingly in this place it will 

 be sufficient to give an account of the relations of the tracts. For 

 a more detailed study of the nerve cells and the relations of the 



