Plate XLVI 



Fig. i8. Photomicrograph of frontal section in the plane of the mandibular 



nerve, from an embryo of 9 millimeters. Columbia Collection, No. 26S, 



X 115, reduced to f. 

 Fk;. iq. Photomicrograph of frontal section in the plane of the mandibular 



nerve, from an embryo of g millimeters. Columbia Collection, No. 106, 



X 115, reduced to ?. 



