THE NERVOUS SYSTEM. 



487 



FIG. 417. 



FIG. 418. 



mle 



mli 



FIG. 419. 



mle 



a 



FIG. 420. 



FIG. 417. From the neural tube of an embryo rabbit shortly before the closure of the tube, g, Germi- 



nal or dividing cell; m, peripheral zone, position of the later marginal layer. Jfw. 

 FIG. 418. Pig of 5 mm., unflexed. Just after closure of the neural tube. Segment of a vertical 



section of the lateral wall of the tube, g, Germinal cells; m, beginning of marginal layer; 



mil, internal limiting membrane; r, radial columns of protoplasm. The resting nuclei lie in 



the inner or nuclear layer. Hardesty. 



