1890. j MICROSCOPICAL JOURNAL. 7 



first two form segments extending from tlie caudcal tip to 

 the olfactory lobes. The rima divides the mesal segment 

 into two parts, the dorsal or hippocarapal and the ventral 

 or tenial. At the porta the tenial unites vi^ith the thalamus. 

 Cephalad of the porta, the hippocampal, unites with an 

 outgrowth of the terma, the termatic segment; so that in 

 the cephalic part of the brain the same complete delta 

 form is re-established. 



21. Sulci which enter the porta indicate that the hip- 

 pocampal, termatic, striatal and tenial segments of the 

 cerebrum have a representative in the mesal wall of the 

 aula cephalic part of the third ventricle). 



22. In both the sparrow and the turtle the striatal limb 

 of the delta has a secondary thickening which is compar- 

 able with the caudatum of mammals. 



23. The porta of the embryo sparrow is bifurcated by 

 the intrusion of the caudatum into the aula. In the adult 

 this intrusion is crowded into insignificance by surround- 

 ing parts. The two sulci of the aula which enter these 

 parts of the porta can be traced upon the wall of the 

 paracoele, one extending cephalad and the other caudad. 

 On the aulic surface these sulci pass ventrad with no ap- 

 pearance of turning caudad to form the aulix or sulcus 

 of Monro as the theory of his would se^m to demand. 

 Comparable sulci entering the porta were found in the 

 turtle although the caudatum does not intrude into the 

 aula. 



24. The significance of other sulci was considered. (1) 

 Those which indicate the boundary of a primal mesal 

 membrane ; as in cerebellum, and at the crista ; (2) those 

 occurring at tlie edge of solid parietes as in the formation 

 of parts of the oblongata as shown by His or of the cortex 

 of the cerebellum as shown by Herrick ; (3) those occur- 

 ring in more solid parts and whose walls finally coalesce 

 to form a cell nidus. 



