Wilder.] 55^ [July 15, 



Had the postcommissura been left, the intervening space would be a fora- 

 men, Fm. conarii. 



The shallow depression of the ventricaudal surface of each hemisphere 

 just laterad of the splenium, represents the area of contact of the opticus. 



The cerebral fissures are markedly unsymmetrical, and thus in contrast 

 with those of fig. 5. The right F. postrldnalis (F. prJi.) is the longer, and 

 the right postsylvirjjia (F. ps.) joins the F. supersylmana, although the place 

 of union does not appear in the figure. On the contrary, by reason of the 

 perspective, it seems to be joined by the F. medtlateralis (F. ml). 



The LlLl. Jiypocamparum have their proper rounded form in this 

 preparation. 



Part of the (liacoelia (dc.) appears dorsad of the medicommissura, and 

 part on its ventral side. In man, the commissure is smaller, and the ccelia 

 correspondingly more extensive. On account of the removal of the hy- 

 pophysis and infundibulum, the diaccelia opens freely at the Fm, iiifundi- 

 buli {Fm. inf.). 



Fig. 7. — The dorsal aspect of the Diencephalon (thalami and genicu- 

 lata), and of the Mesencephalon (optici and postoptici). 



From preps. 397 and 494, adult 9 $, 423, a nearly adult 9, and 506. 

 Enlarged two diameters. 



The principal features of this figure were drawn from prep. 506. The 

 preparation was made by lifting the caudal ends of the hemispheres, and 

 gradually separating them, with the callosum, fornix and velum, from the 

 subjacent parts. The epen. and meten. were then removed by a transec- 

 tion just caudad of the postoptici. 



The valvula (vv.) was torn from prep. 506; so it is drawn as it appeared 

 in prep. 494, after inflation by blowing air from the diaccelia through the 

 mesocoslia or iter. 



The Commissura habenarum {Gs. Ji.) is really more distinct in prep. 397 

 than appeal's in the figure. The habense (7i. ), their sulci {SI. h.) and the 

 lines of reflection of the endyma are taken from prep. 422, and their dis- 

 tinctness is not exaggerated in the figure. Their morphical significance is 

 to be noted in connection with the general question of coelian circumscrip- 

 tion. Upon this point, see a brief note in " Science " {12). 



The complete roof of the diaccelia, the diateki {dtl.), is shown in fig. 10. 



As compared with the homologous parts in man, the feline pastoptiei 

 {pop.) and geniculata {p>gn2ind prgn.) are larger, while the tlialami [th.) 

 seem to be only the mesal continuations of the prcegeniculata {prgn.), and 

 to lack altogether the pulvinar or " posterior tubercle " of man. 



Fig. 8. — The caudal aspect of the Mesencephalon, with pails of the 

 adjoining regions. From prep. 506. 



The plane of transection coincides nearly with the caudal surface of the 

 postoptici {pop.), and has divided the p)ons {pn.), a little caudad of its 

 middle. The valoula {vv.) was torn from this preparation, and the line of 

 its attachment is not distinctly shown. Something of its position may be 

 judged from fig. 7. The caudal orifice of the iter or mesocoilia {msc.) is 



