ABBREVIATIONS 



D., diencephalon 



I.D., first diencephalic segment 



II. D., second diencephalic segment 



D.C.P., diencephalic choroid plexus 



D.R.P., diencephalic roof plate 



E., epiphysis 



E.A., epiphysal arch 



F.B., forebrain 



P.M., foramen of Munro 



H., hypophysis 



Hm., hemisphere 



L.C.P., lateral choroid plexus (telen- 



cephalic) 

 L.T., lamina terminalis 

 L.V., lateral ventricle 



M., mesencephalon 



M.B., midbrain 



O.C, optic commissure 



P., paraphysis 



P. I., pars intercalaris 



P.V.A., postvelar arch 



P.V.T., postvelar tubules or diver- 



ticuli 

 P.C., posterior commissure 

 S.C., superior commissure 

 T., telencephalon 

 T.R.P., telencephalic roof plate 

 Th., thalamus 

 v., velum transversum 



PLATE 1 



EXPLANATION OF FIGLTIES 



1 Sheep, 9.9 mm. H. E. C, sagittal series, no. 1339. X 20. 



2 Sheep, 14 mm. H. E. C, sagittal series, no. 1330. X 20. 



3 Sheep, 21 mm. H. E. C, sagittal series, no. 1687. X 20. 



104 



