54 Journal of Comparative Neurology, 



description of plate xii. 



SORENSEN. 



Fig. I. Composition drawing from several longitudinal sections of Phry- 

 nosoma coronata, showing the epiphysial structures and parietal nerve and 

 vesicle. The nerve arises from the supra-commissure, while the pineal stalk 

 springs from the roof immediately caudad of the commissure. 



Fig. 2. A single section illustrating the relations of the pineal on a larger 

 scale. The nerve is not shown. 



Fig. J. Median-longitudinal section of the head of a duck embryo at six 



days. 



Fig. 4. Similar section (somewhat oblique) from a later embryo, showing 



relative increase of the prepineal roof of the diencephalon. 



Fig. 5. Enlarged view of the epiphysis figured in 4. 



Fig. 6. View of the roof of the diencephalon and mesencephalon in later 

 duck embryo. 



Fig. 7. Epiphysis in still later stage. 



Refer also to Plate VI. 



Fig. 4. External view of the Epiphysis of Cistudo, from a model com- 

 posed with the aid of the camera lucida from sections. 



Fig. J. Composite section of the same showing the relation of Epiphysis 

 and paraphyses. 



IV. Reversion of the Cerebellum in American Lizards. 

 By P. T. Evans. 

 In the March number of the Journal of Comparative 

 Neurology for 1891, Prof. Herrick calls attention to a forward 

 folding and consequent reversion of the cerebellum in the Scel- 

 oporus undulatus. The passage in question is found on page 

 7, and reads as follows : "In the case of lizards we have ap- 

 parently a completely dissimilar plan of structure. Here the 

 gray matter is dorsal and white ventral (Plate IV, Figs. 4 and 

 5). This reversal of the two layers is explained, upon a more 

 careful examination, as the product of a complete forward and 

 median fold of the caudal and lateral margins of the cerebellum 

 (compare Plate IV, Figs. 6-9). This is but the completion of 

 the process indicated by the incipient retroflexion seen in the 

 turtle. The result of this fold is the formation of an actual 

 cavity surrounded caudad and laterad by the white (morpho- 

 logically dorsal) zone of cerebellum. Thus the fusion of the 

 lateral margin, or, more accurately, the union of the whole lat- 

 ero-caudal reflected margin due to a general cephalo-median in- 

 crease, produces the hollow organ just described." 



