120 



B. F. KINGSBURY 



alternative to that of His. However, inasmuch as I have in 

 this jiai^or attempted to show that from the actual facts of struc- 

 ture the fl()()r-])late extends no farther forward than the fovea 

 isthmi, and that theoretic considerations strongly speak against 

 its extending to the extreme anterior end of the neural plate as 

 the diagram of His indicates that it does, a simple diagram (fig. 

 0) will serve to make clear what are the conclusions to which in. 



B G 

 D 



Fig. 6 Diagram to llustrate the interpretation of the cephalic portion of the 

 neural plate. A., the region of the retinal area(s) ; B.. the region of the olfactory 

 lobes (and cerebrum); C, cephalic end of the floor-plate or sutura neurochordalis 

 (fovea isthmi in the neural tube); D., the floor-plate (sutura neurochordalis); 

 G., primary motor zone, lamina basalis; H., primary sensory zone, alar plate; 

 III, N. oculomotorii; IV, N. trochlearis. 



my opinion one is logically led, both from fact and from theory. 

 In the diagram it will be noted that the alar plate and the basal 

 plate, primary sensorj^ and motor zones, are indicated as extending 

 around from side to side 'anterior' to the cephalic end of the floor- 

 plate or neurochordal suture at whose cephalic end the fovea 

 isthmi appears in the neural tube. The retinal area occupies the 

 more cephalic portion of the alar lamina while the nucleus oculo- 



