388 W. H. C4ASKELL. 



In his description (p. 285) of this figure he says, speaking 

 of Meynert^s bundles, " Dicht iiber der Haubeneinschnilrung 

 [i.e. the large ventral fissure which separates the pre-chordal 

 and epichordal portions of the brain] losen sich die Biindel 

 auf; ein grosser Theil der Fasern fahrt pinselformig gegen die 

 Mediane aus einander und bildet hier einen asymmetrischen, 

 eigenthiimlich hellen und ausserst feinkornigen Korper, welcher 

 der Haubeneinschnilrung direct aufgesetzt ist.'' 



This description expresses very well the appearance of the 

 termination of this occluded tube as it appears in my speci- 

 mens, with the exception that I have not noticed any appearance 

 of asymmetry in the peculiar transparent termination of this 

 tube. The meaning of this tube is to my mind perfectly 

 plain ; we see here more clearly than in any other Vertebrate 

 that a median tube formed of ependyma, continuous with that 

 of the central cavity of the brain, is lying freely on the 

 surface of the brain in the exact position where the cesophagus 

 ought to be found if the central cavity of the brain is the 

 cavity of the cephalic stomach of a Crustacean-like ancestor. 

 This tube, to my mind, cannot be called lobus infundibuli ; 

 it is not homologous with the paired lobi infundibuli of other 

 fishes : it is the same in position and in meaning as the median 

 tube which I have described (1) in the tuber cinereum of the 

 sheep ; it corresponds with the median prolongation fi'om the 

 saccus vasculosus Avhich I have described in the brain of the 

 dog-fish, where this same tube exists in addition to the paii'ed 

 lobi infundibuli. The difference in its apparent position in the 

 dog-fish and in the lamprey is due simply to the more extensive 

 cranial flexure which has taken place in the former animal. 



In fact, the paired diverticula from the canal of the iufundi- 

 bulum which form the cavities of the lobi infundibuli open 

 into the infundibular canal between the saccus vasculosus 

 and the third ventricle ; w^hile the so-called lobus infundibuli 

 of the lamprey, and I presume also of the Amphibian, is a 

 posterior median prolongation from the saccus vasculosus 

 itself, exactly as is found also in the dog-fish, in the siieep, &c. 



We see, then, in the lowest Vertebrate, the presence not only 



