1^ JOUKNAI. (>!• C(>Mr.\K\Tl\ K NkI H(>1.(><;V. 



development corresponds to the course of evolution as 

 deduced from the adult conditions of various reptiles 

 seems equally clear, and the whole argument forms a 

 beautiful illustration of the interdependence of all biologi- 

 cal sciences. (' ) 



II.— TOPOGRAPHY AND HISTOLOGY OF THE BRAIN OF 

 CERTAIN REPTILES. 



Materials. — The brief notes here following, like the first 

 paper of the series, published in the Jotirnal of the Cincin- 

 nati Society of Natural History for 1890, are to be regarded 

 as materials for elaboration in a more systematic wa}' when 

 they shall have accumulated sufficiently to make such sys- 

 tematic treatment profitable. The present instalment deals 

 primarily with the prosencephalon, especially the distribu- 

 tion of its cells and commissures. The materials consist of 

 a number of brains of the small lizard Sceloporus undulatus , 

 locally abundant in Scioto county, adult and embryonic 

 brains of the black-snake, and a specimen of the turtle, 

 Aspidonectes spinifer. 



Topographv and external form of the lizard brain. — The 

 form of each hemisphere is, roughly speaking and exclusive 

 of the elongate olfactory lobe, a triangular pyramid*. In 

 horizontal section the angle formed by the median and cau- 

 dad planes bounding the hemisphere is about 120^. The 

 third side is a gentle curve more rapidly arching to the 

 cephalad extremity. The diencephalon is included within 

 the reentrant angle formed by the caudad planes of the two 

 hemispheres, for externally the latero-caudad angle of the 

 hemisphere is in contact with the cephalo-lateral projection 



I The close approach made by Obersteiner to the view here announced is indica- 

 ted by the following quotation from Meynert, Psychiatry, p. ii6: 



" According to Obersteiner, the cerebellar cortex in the child is covered by a layer of 

 formative cells, wnich are transformed into spindle-shaped fibrils, thus constituting an 

 luaermost stratum of the pia mater." 



