480 B. F. KINGSBURY 
of the figures of plates 2 and 3. The important relations of 
notochord and prechordal plate are more adequately discussed 
by Adelmann (’22). 
CONCLUSIONS 
In the foregoing pages the four interpretations outlined in the 
introductory paragraphs of this paper have been examined from 
the three points of view proposed on the question of fact, and the 
conclusion is safe, I think, that the His interpretation and that of 
Schulte and Tilney fail to satisfy the requirements. Johnston’s 
observations have been confirmed in the essential feature that the 
neural plate terminates with the chiasmatic ridge and that the 
primitive infundibular furrow is likewise a primitive optic furrow. 
My own interpretation has added what I regard as an important 
point—the recognition of a primitive continuity of nervous 
parietes in the brain anterior to (cephalad of) the notochordal 
axis, together with a more correct evaluation and limitation of 
the sutura neurochordalis of His. It is felt that there has been 
given an interpretation also consistent with the actual facts of 
brain growth and with the pattern of vertebrate ontogeny which 
was less apparent if the approach was from the neurological side 
as in the case of the researches of Johnston and Schulte and 
Tilney. As has been insisted earlier in this paper, the develop- 
mental origin of the brain plate and the morphogenesis of the 
brain are primarily embryological questions inseparable from the 
pattern of morphogenesis of the head and of the body as a whole. 
It is not my intention to consider in any detail the embryo- 
logic aspects of the problem in this place; it is, however, advan- 
tageous to briefly mention some contributory evidence from the 
embryological side. Stated succinctly, it is clear that the verte- 
brate brain arises from the dorsal blastoporic lip which by growth 
effecting essentially a potential closure of the blastopore, produces 
an arrangement of material in the neural plate illustrated in figure 
2, D, in which the neurochordal suture marks such a line of 
‘closure,’ while the floor plate is a differentiation along this line 
expressing the primitively bilateral character of the growth of 
nervous material. Beneath the neural plate the mesoderm and 
