354 Robert J. Terry. 



to the paraphysis has usually the form of a dome. Since Minot 

 ('01) named it the paraphyseal arch and demonstrated that the 

 paraphysis arises from it, its presence has been recognized in 

 all the vertebrate classes. (Comp. Dexter, '02; Warren,* '05; 

 Kerr, '03; Johnston, '09).' 



Ill Conclusions 



1. A. The six morphological divisions of the fore-brain roof 

 recognized by Minot are present in Opsanus, and probably also 

 in Salmo, Salvelinus and Amia. 



B. These divisions, in the form of arches and alternating 

 projections into the ventricle, are not all present at the same 

 time in Opsanus as in Acanthias. 



2. A. A pars intercalaris is to be seen as an independent segment 

 of the brain-roof between the posterior commissure and the epi- 

 physis in embryos of Opsanus 3.5 mm. long. 



B. In the adult it remains as a thick stretch of ependyma, 

 supporting the anterior stratum of the posterior commissure. 



3. A. There are two epiphyses connected with the brain of the 

 toad-fish, one of them being a mere rudiment. 



B. The main epiphysis lies in the mid-line and develops a 

 stalk and end-vesicle. 



C. The rudimentary organ makes its appearance some time 

 after the definitive epiphysis is differentiated, lies at first to the 

 left and a little in advance of it and subsequently migrates 

 forward into the region of the post-velar arch. 



D. The origin of these organs is entirely independent, the 

 one from the other. 



E. Both epiphyses are originally solid outgrowths, the main 

 organ springing from the epiphyseal arch, the rudiment from 

 the diencephalic roof behind the superior commissure after 

 the disappearance of the epiphyseal arch. 



F. The cavity which develops secondarily in the end-vesicle 



* Warren, John. On the paraphysis and pineal region in Lacerta and Chrysemis 

 marginata. Assoc. Am. Anat. 25th Session. Boston, December 30, 1909. 



