l8 JorRX.M. OF COMPARATIVK NEUROLOGY. 



caudad and entering the thalamus from the caudo-lateral 

 aspect of the ventral part of the hemisphere. This tract 

 doubtless corresponds to the direct thalamus tract noticed in 

 the lizard. 



In horizontal sections of the ventral part of the hemi- 

 sphere in the lizard a large central mass can be distin- 

 guished, which, although it may contain homologues of 

 part, at least, of the striatum, may here be called simply 

 central lobe. It receives the pyramidal tracts. 



There is ectad to this a lenticular gray mass, with few or 

 inconspicuous cells, which is separated both from the lateral 

 cortex and the central lobe by fibre-tracts. There is a cer- 

 tain resemblance to the claustrum, though no such homology 

 is suggested for what may be termed the lenticular nidulus. 

 Peripherad to this nidulus is the narrow parieto-frontal lobe 

 of the cortex, with its densely-packed pyramidal cells. 



Further cephalad and dorsad a small triangular cluster, 

 apparently connected with the lenticular nidulus, reaches 

 the surface, forming a frontal lobe. Still further dorsad a 

 small oblique and very dense lamina of closely-packed cells 

 of the flask variety appears. This is the most conspicuous 

 of all the lobes in section, and may be termed the fronto- 

 median lobe. In transverse sections the fronto-median lobe 

 appears as a very densely cellular band of nearly uniform 

 width, occupying the middle of the width of the tectum 

 cerebri, and separated from the ventricle by the tracts pas- 

 sing cephalo-dorsad from the callosum via the intra-ven- 

 tricular lobe. There are very evident connective fibres 

 springing from the ventricular epithelium and passing 

 through the callosal tract toward the surface at the median 

 fissure. Upon these fibres are the usual " glia" corpuscles, 

 with elongate outlines and granular texture. The cells of 

 the fronto-median lobe are fusiform elements of the sensory 

 type, except cephalad, where there is an admixture of the 

 deeply staining pyramidal variety. The contrast between 

 these cells and those of the frontal lobe is very striking. 



