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thalamus is hei^e filled with fusiform cells (Figf. 3, Plate XII; 

 Fig. 13, Plate IV, and Fig. i(a), Plate IV. 



At the point where the nates begin to appear in the 

 section (Fig. i, Plate IV), a strong decussation or commis- 

 sural system appears connecting the right and left peduncu- 

 lar regions. The decussation is a large one, and is separated 

 in its ventral course from the chiasm by dark fibres which 

 I have homologized in the alligator with the ansulate fibres. 



The so-called commissure of von Gudden, above described, 

 extends as far caudad as to the front of the infundibulum, 

 which occupies a position beneath the mesencephalon, the 

 thalamus having been caudo-ventrally appressed upon the 

 corpora quadrigemina. 



The ventral region of the thalamus may next be noticed. 

 The chiasm is very perfect in the snake. The optic fibres 

 being collected in small bundles, each bundle being crossed 

 by a corresponding bundle of the opposite side. Each of 

 the small bundles is enwrapped with a transverse meshwork 

 of connective fibres, thickly set with deeply staining trans- 

 verse inoblasts, giving to the optic nerve a different appear- 

 ance from that of any other cranial nerve. 



The nidulus fornicis inferior consists of two sharply- 

 defined cell-clustres immediately cephalo-ventral of the in- 

 terpeduncular nidulus, occupying the caudad aspect of the 

 tuber cinereum. The cells are fusiform and transversely 

 placed. The two niduli are separated in the lizard by a 

 considerable interval. While these cell-clusters ought to 

 be unhesitatingly homologized with the mammillary, no 

 ascending tract to the thalamus was seen, and it may be 

 well to use a name not implying any homology. 



In the caudal portion of the tuber at the level of the 

 chiasm, in both the black snake and lizard, are two niduli 

 of pyramidal or irregularly multipolar cells, rather larger 

 than those of the surrounding gray matter. They occupy 

 a position some distance laterad from the median line, and 

 are quite distinct from the interpeduncular nidulus, as well 



