Herrick, Morphology of Xervons Svstcm. 33 



cells. The medullary portion lying near the ventricle con- 

 tains cells of two sorts, the ordinary Deiter cells, with clear 

 granular nucleus and no obvious cell body, and deeply stain- 

 ing nuclei of smaller size, which perhaps belong to the con- 

 nective tissue system. There is a small branch ot the olfac- 

 tory (Plate III, Fig. 4, ol. 2) which, after separating from 

 the main portion, passes along the ventral surface of the 

 bulb, without entering it, until it terminates in a detached 

 ventro-caudad portion of the glomerular layer. 



The structure of the pyriform lobe is illustrated by Fig. 

 14, Plate X. The small, irregularly pyramidal or multipolar 

 cells scattered among the fusiform remind one at once of the 

 corresponding region in mammals. The chief difference 

 between these cells and those of the motor type lies in 

 their smaller size, greater irregularity and greater avidity 

 for stains. 



The basi-occipital lobe is considerably developed, espe- 

 cially immediately dorsad to the basal part of the ventricle, 

 and projects as a distinct tuber into the posterior cornu (Plate 

 III, Fig. 3, ol.). Dorsad and cephalad to the basi-occipital 

 lobe is a tract forming a curved roof-like partition between 

 it and cephalad parts of the brain. This tract is densely 

 filled with spindle-cells with axes chiefly parallel to the 

 general direction of the tract, descending from the dorso- , 

 cephalad angle of the posterior cornu obliquely cephalo- 

 ventrad to the basal part of the ventricle. Thence the 

 tracts and accompanying cells seem to pass caudo-laterad 

 toward the peduncles. A considerable axial portion of the 

 cerebrum lies beneath (ventral to) the anterior cornu, but 

 may be regarded as a part of the central lobe. 



All of these axial portions, but especially the occipito- 

 basal, contain rosette-like clusters of fusiform cells. These 

 are obviously due to successive subdivision of cells; in fact, 

 all stages of such subdivision may be found, extending from 

 single cells with double nuclei to rosette-like clusters within 

 clear spaces in the neuroglia. Tt sometimes appears as 



