The Pineal Region in Teleosts. 355 



and stalk of the main epiphysis includes a weak meshwork of 

 protoplasmic processes continuous with the surrounding walls. 



G. Continuity between the epiphysis and ectoderm was not 

 observed; the fibers that extend between the end- vesicle and the 

 overlying parts are mesenchymal in origin. 



H. There is no parietal foramen and no differentiation of 

 the epidermis of the epiphyseal region in Opsanus. 



I. A nerve connection between the epiphysis and lateral 

 line system does not obtain. 



J. A pineal nerve was not discovered. 



K. There are two epiphyses in Salvelinus, the chief organ 

 being median in position, the subordinate outgrowth to the left 

 of the former. 



4. A. The posterior commissure of Opsanus has its origin 

 in the ectoglia of the brain-roof. 



B. In teleosts the commissure is divided into two parts, 

 the one associated with the mid-brain, the other with the interca- 

 lated part of the diencephalon. 



5. A. The superior commissure lies, in the toad-fish, imme- 

 diately anterior to the base of the epiphysis. 



B. It arises in the ectoglia of the diencephalic roof, retains 

 the relation of an ectoglia layer in the brain-wall of the adult 

 and may be regarded as an incomplete ectoglia stratum of the 

 post-velar arch. 



6. A. The post- velar arch attains its maximum extent in the 

 embryos of Opsanus and early begins to diminish and finally 

 disappears. 



B. Its place is taken by the velum in its backward growth. 



C. Its epithelium probably becomes incorporated with the 

 velum. 



7. A. In the development of the velum of Opsanus, a trans- 

 verse fold and a median lobe are formed, the latter differentiating 

 as a choroid plexus of the fore-brain ventricle. 



B. The velum of Amieurus embryos is rudimentary. 



8. A rudimentary paraphyseal organ is developed from the 

 paraphyseal arch, appearing later than the epiphysis and dis- 

 appearing during the early larval life of the toad-fish. 



