1 6 Journal of Comparative Neurology. 



in the Batrachia. In the toad that part of the medullary 

 tube which lies immediately in front of the mesencephalon 

 closes last and remains in connection with the epidermis by a 

 short solid bridge even after the separation of the tube. Soon 

 an evagination of the ventricle pushes forward into the process, 

 breaking its connection with the epidermis. The inferior part 

 of the hollow projection is afterwards constricted forming a 

 small vesicle lying over the roof of the diencephalon, to which 

 it is joined by a solid stalk. Later the stalk lengthens consid- 

 erably, and the cavity of the vesicle is filled up by the develop- 

 ment of the cells. Finally, the cells are partly transformed 

 into nerve cells ; nerve fibres and a silvery white substance, are 

 then developed, the latter being homologized with the brain 

 sand of higher vertebrates. The pineal remains in very close 

 relation to the epidermis. Its stalk is attenuated to a fine 

 thread and becomes imbedded in the dura mater and the skull. 

 Thus in Batrachia the pineal comes to lie on the outside of the 

 skull chamber on the arch of the head. Further Gotte (p. 316) 

 remarks that this structure on the forehead of the toad was 

 already discovered by Stieda, but was wrongly regarded as a 

 parietal gland ( Reichert's Archiv, 1865). All the remaining 

 authors ( Wyman, Ecker, Leydig, Rathke, Gegenbaur) who 

 described the pineal of batrachians as situated in the skull cavity 

 have confused the vascular plexus of the third ventricle with the 

 pineal. Gotte made no personal investigations concerning the 

 gland in other vertebrates and only remarks that he cannot de- 

 cide whether their gland corresponds to the entire pineal of 

 batrachians or only to the basal portion remaining in the skull 

 cavity ; after some observations on birds and Selachians the first 

 view seemed more probable. Finally he remarks that the pineal 

 process cannot be considered as a simple evagination of the mid- 

 brain, for it is the last remnant of the union of the brain and the 

 epidermis and the lack of this union may perhaps correspond to 

 the cleft in the embryonic brain of the Amphioxus as described 

 by Kowalewsky. 



Lieberkiihn {s°~7 l ) fi fS t discovered the development of 

 follicles from the processus r pinealis in birds. He briefly de- 



