Evans, Neurological Laboratory Notes. 55 



Dr. Ludwig Edinger, in his report^ upon the investigation 

 of the anatomy of the central nervous system for I891, offers 

 the following criticism: " Herrick comes to the conclusion, as 

 a result of the tracing of the various layers of the cerebellum 

 thoughout the vertebrate series, that in the reptilia there pre- 

 vails a forward reversion of the cerebellum in such a way that 

 parts which before lay upon the surface come to lie ventrally. 

 The preparations which were prepared by the carmine method 

 do not enforce this conclusion." 



The last statement is erroneous. The carmine method was 

 not used. Being a student of Prof. Herrick's, I was led to in- 

 vestigate this point in other species since we have received more 

 material. An examination of the brain of Phrynosoma as seen 

 in Fig. 8, Plate VI, reveals the forward reversion very plainly. 

 It is not possible to be mistaken in this. In noticing this figure 

 it is to be seen that there is no plexus. This was torn away in 

 order that this forward reversion might be seen. The tearing 

 away of the plexus leaves the fourth ventrical uncovered. It 

 is also noticed in Fig. 19 — c, Plate V, Vol. 55, No. i, of the 

 Zeitschrift fiir Wissenschaftliche Zoologie, that the same thing 

 exists in Iguana, but Dr. Meyer doest not seem to have noticed 

 it. In the study of sections of the species of which Fig. i, 

 Plate XII and Fig. 10, Plate V, are representative, I find the 

 histology to be the same as that of all reptilia. This forward 

 reversion of the cerebellum gives the ventral surface the dorsal 

 position and the white upper layer is inverted over the optic 

 lobes. In comparing the sections from which figures 4, 5 and 

 6, Plate IV, of the March number, Vol. I, were made, with the 

 sections of which P'igs. 10, 11 and 12, Plate V, were taken, I 

 find that the histology agrees in every particular, and the histol 

 ogy of the part spoken of as the plexus in Figs. 10, 1 1 and 12, 

 Plate V, agrees with the histology of the plexi. There can be 

 no doubt that this reversion is a fact. We find the same thing 

 in the Iguana, Sceloporus, and in Phrynosoma the same condi- 

 tion exists, and, curiously enough, all these lizards also have 

 the parietal eye. 



1 Schmidt's Jahrbiicher der gesaminten Medicin Bd. CCXXXVI, p. 20. 



