104 Journal of Comparative Neurology. 



cism has, as far as I am able to ascertain, never been made. 

 The division into epencephalon and metencephalon has 

 been made by reason of changes of the so-called epencephalic 

 portion which have a late appearance, both ontogenetically and 

 phylogenetically. 



The difficulty in dividing the ventricle lies in finding the 

 point where the transverse line should be drawn. 



In the division generally accepted, this line falls at the 

 widest portion of the lateral recesses and as the oblongata term- 

 inates at the pons flexure the line must be taken as the flexure. 

 Now the lateral recesses are generally included in the epen- 

 cephalic segment, as is evinced by their name parepiccelia 

 (Wilder). 



As has already been shown, the roof of the lateral recesses 

 is formed from cerebellum, both in embryonal and adult stages, 

 yet the floor is formed by oblongata, consequently they can be 

 included in neither segment. Likewise the portion of the ven- 

 tricle lying between them is equally indivisible. 



Reference to Figs. 12, 13, and 14 will help to elucidate 

 this point. 



In Fig. 12 the terms epicoele and metacoele are easily appli- 

 cable; also they can be applied in Fig. 13, but cannot be in 

 Fig. 14. The same can be seen in comparing Figs. 3 and 7 

 with Figs. 4 and 8. 



The reconstructions also demonstrate the same thing. Figs. 

 18, 19 and 20. 



Sagittal sections at the meson do not help to elucidate 

 this point. 



It may be said that we can divide the lateral recesses and 

 relegate a portion to each segment. This, however, seems to 

 be out of the question. 



Finally, if one follows the development of the rhomboidal 

 fossa the similarity displayed throughout cannot help but im- 

 press him that the division is artificial and needless. While the 

 use of the terms epencephalon and metencephlon is convenient 

 in the description of certain portions, yet it only leads to em- 

 barrassment in that of other portions. 



