Stroud, Mavimalian Cerebelliun. 105 



plexus to the tela. It extends around the lateral and dorsal sides of the brain 

 tube like a girdle, therefore the term cestus [est.) is proposed to indicate it. 

 This is a very interesting specimen and apparently presents a condition identical 

 with that shown in the human embryos, Figs. 52 to 55, PI. V. 



Fig. 7. Shows the left lateral aspect of the same specimen ; here the audi- 

 tory region is quite large, the cestus shows clearly and the plexus may be dimly 

 seen through the thin semi-transparent tela. 



Figs. S and g. Embryo kitten 40 mm. long (x 11), prepared by Dr. P. A. 

 Fish. Shows, 



a. The caudal extension and bifid extremity of the mesencephal. This 

 appearance is very characteristic. 



b. The lateral protons of the cerebellum have now fused at the meson. 

 It seems probable that the change has been brought about in the following 

 manner. Each lateral proton has grown by an increase in thickness and has 

 gradually extended itself by a sort of proliferation cephalad, dorsad, and mesad 

 till at last it has met the proton of the opposite side of the brain tube at the 

 meson and has fused with it. Thus the deckplate has been obliterated. From 

 now on we have to deal with a single structure instead of with two. The lat- 

 eral portions, however, have a much greater mass than the middle part which 

 is still thin. This relative proportion continues for some time. The vermis of 

 the adult cerebellum is comparatively late in its development. The remaining 

 parts are self explanatory. 



Fig. g. Shows the left lateral aspect of the same specimen. There is a 

 small elevation at the cephalo-lateral extremity which shows that the prepileum 

 has begun to be differentiated, but the entire region of the pre- and postpileum 

 is indicated under the general term pileiim. A shallow furrow marks the floc- 

 cular sulcus. The other parts are self explanatory. 



Figs. 10 and II. Embryo kitten 36 mm. long, No. 3340 (x 15). Fig. 10 

 shows the dorsal aspect of the cerebellum which has now begun to be differ- 

 entiated into regions which persist through life. It appears that the earlier 

 changes begin laterad and proceed mesad. From an examination of the sur- 

 face the mesal part appears to be still quite thin. At this stage at least two of 

 the primary furrows have appeared. In the lateral regions two elevations sep- 

 arated by a shallow furrow — the parafloccular sulcus — ^have appeared. These 

 elevations constitute the pileum and the paraflocculus, shown in profile in Fig. 

 10. Fig. II shows a face view. The floccular sulcus extends transversely clear 

 across the cerebellum. Dorsad of it there is a slight narrow depression which 

 probably represents the later nodular sulcus. At this stage there is a dorso- 

 caudal extension of the cerebellum ; at the meson there is a distinct notch, 

 barely perceptible in Fig. 8. It shows very clearly in Fig. 13. Fig. lo also 

 shows the kilos, cestus, tela, and plexus quite clearly. 



Fig. II. Shows the first real demarcation of the cerebellum into distinct 

 regions, the pileum and the paraflocculus. A little later the pileum is divided 

 into two regions, prepileum and postpileum, by a new sulcus the interpilear 

 sulcus. See Fig. 15, PI. II. Fig. 11 also shows the floccular sulcus, the kilos, 

 the parepicoele, and the plexus which shows through the tela. During the 

 dissection the tela was torn away from the kilos. Its lines of attachment is in- 



