66 Journal of Comparative Neurology. 



The bundle which emerges dorsad is doubtless the tract of 

 the commissura transversa, together with the specific fibres of 

 the nidulus to the dorsal regions of the thalamus. 



The tracts which are associated with the nidulus ruber are 

 the following : The commissura horizontalis tract, which passes 

 through it in a broad curve so that it enters from a cephalo- ven- 

 tral, and emerges in a cephalo-dorsal direction ; 2, a direct me- 

 dulla tract, springing from the above mentioned at its dorsal 

 union with the nidulus, which passes directly caudad through 

 the loop of the commissura ansulata, etc., and enters the me- 

 dulla in a cando-dorsal direction ; this tract is shown in Figs, i 

 and 2, Plate VI., and must not be confused with the cerebellar 

 peduncle dorsad, nor the main body of the dorsal peduncle which 

 lies caudo. ventrad of it; 3, the dorsal peduncle of the ruber, 

 a tract with a mixture of non medullated fibres and cells leading 

 toward the thalamus ventrad of the dorsal part of the com. hor- 

 izontalis ; 4, the dorsal peduncular fibres, embracing the nid- 

 ulus from all sides except dorsad, so that it is difficult to distin- 

 guish special tracts. The fibres passing to the cerebrum 

 constitute a comjjact bundle. There is a distinct ventral bundle 

 going toward the medulla of the hypoaria ( niger ), and the tract 

 passing from the medulla in its dorsolateral aspects in a tortuous 

 course to the caudo-ventral region of the ruber. Other minor 

 fibre tracts may for the present be ignored. 



In amphibia the nidulus ruber is not distinct, although it is 

 clearly indicated by Reissner '. 



This mass lies in the homologous position, dorsad of the 

 infundibulum where the latter expands to simulate the hypoaria 

 though they are not holiow. It is described by Reissner as 

 follows: " Es sind iibrigens die friiher zerstreuten Bundel zu 

 einem einzigen, freilich nicht gang compacten vereiriigt, in dem- 

 selben und um dasselbe liegen korner in grosser Menge." The 

 combination of the various bundles of the thalamus, the accum- 

 ulation of numerous cells in a meshwork, and the position 

 make the identification probable. It will be observed by a 

 study of the plates accompanying Reissner's memoir that caudo- 



I. Bail des ceiitialnervensystems der ungeschwaiizten Batrachien. 

 Plate VII, Fig. XI. 



