EARLY DEVELOPMENT OF HEMISPHERES 279 
fine hair was inserted far enough to prevent its extrusion it became 
evident that the imbedding of the hair in the tissue deep in the 
embryo prevented its following the ventral path of the neuro- 
pore. However, by making a slight wound in the ventral lip 
of the neuropore and staining it with Nile-blue sulphate, accord- 
ing to the method of Detwiler (’17), it was found that the stained 
area could be followed throughout the subsequent development. 
In fact, the Nile-blue sulphate remained in the tissue for a period 
QrEy Co) 
Fig. 1 Ventral view of Amblystoma embryo, showing area of ventral lip of 
neuropore stained with Nile-blue sulphate, stippled. X 12. 
Fig.2 Same embryo 24 hours later. X 12. 
Fig.3 Lateral view of same embryo 48 hours after operation. 12. 
Fig.4 Lateral view of same embryo 72 hours after operation. X 12. 
Fig.5 Lateral view of same embryo 96 hours after operation. X 12. 
of twenty-one days. A series of drawings showing the position 
of this stained area is given in figures 1 to 5, representing an 
elapse of four days. A sagittal graphic reconstruction of the 
brain of the embryo shown in figure 5 is given in figure 6. The 
region of the stained area is indicated in the figure, rn. 
The material which makes up the ventral lip of the neuropore 
produces the ridge in the floor of the neural tube to which John- 
ston has given the name of the terminal ridge (fig. 6, tr.). It is 
evident, therefore, that the closure of the lateral lips of the neuro- 
pore produces the lamina terminalis which ends not in the pre- 
