363 
fourth day of incubation. For the purposes of this paper, only a few 
of the specimens will be mentioned. 
Fig. 11 is a camera sketch of an embryo with open neural groove, 
24 hours old. In front of the first somite, 11 transverse grooves are 
present. They are not restricted to the neural folds but pass across 
the base of the neural groove. There are 111/, segments in front 
of the first mesoblastic somite as was also shown by Locy and HaYner. 
Fig. 12 shows the external surface of the encephalon of the same 
Bweaw ag & & en ı“ 
N 
Fig. 11. | Fig. 12. Fig. 13. 
Fig. 11. Dorsal view of a Chick embryo with 4 somites, 231/, hours old. 
1, 2, 3 ete. neural segments. “% 27 diameters. 
Fig. 12. Anterior portion of the neural groove of the same embryo as represented 
by Fig. 11, Right profile view. c anterior limit of mid-brain; 7, 2, 3 etc. neural seg- 
ments. >< 50 diameters, 
Fig. 13. Left half of the anterior portion of the divided neural groove of a Chick 
embryo with 3 somites, 23 hours old, Internal surface exposed to view. 1, 2, 3 ete. 
neural segments, >< 50 diameters, 
embryo after the mesoderm has been brushed away. The segments 
are thus rendered more distinct and are seen to extend into the ven- 
tral zones. Fig. 13 shows the inner surface of the left half of a di- 
vided embryo slightly younger than the preceding one. 
