Susanna Phelps G-age 435 



yet are for the most part distinguishable, the auditory following the 

 thickening of the auditory vesicle on the cephalic and lateral portions, 

 that of the Vllth extending without special differentiation into its nerve 

 which forms a union with thickened epithelium at the dorsal end of the 

 1st gill-cleft (Pigs. 1, 11). 



17. Oblongata 5. — In the chick and all mammals examined, this fold 

 lies opposite the otic vesicle but has no connection with it, unless possibly 

 at a very early stage while the ear is merely a thickened plate pushed 

 close to the neural plate. Dr. Johnston called my attention to the fact 

 that such a fold is wanting in Amblystoma and an examination of 

 material at hand, confirms his observation that no fold exists between 

 that to which the Vlllth and IXth nerves are attached, in early stages 

 of Amblystoma. However, in the shark Sewertzoff °' shows such a fold 

 to exist and it seems probable that modelling of the region in Amblystoma 

 might reveal its rudiment. 



18. Oblongata 6. — In all forms examined, this permanent fold has been 

 found connected with the roots of the IXth nerve. 



19. Oblongata 7. — This is a large fold arising at the caudal end of the 

 metatela, extending obliquely cephalad and ending in the floor of the 

 oblongata in close relation to the previous fold. It is connected with the 

 roots of the Xth nerve. Apparently in other specimens, this fold cannot 

 be so clearly defined as the others in the oblongata since it has rarely been 

 recognized. Froriep *^ in one human specimen, and Bradley ^' in the pig, 

 have observed this fold. 



£0, 21. Oblongata 8, 9. — These two pairs of folds are really dorsal 

 pockets extending only through the dorsal half of the neural tube. 

 Opposite their ventral portion, roots of the Xlth nerve arise (Fig. 14). 

 This nerve is interrupted in its course to join the Xth nerve by masses 

 of ganglionic cells. 



The relations of the A'llth, IXth, Xth, and Xlth nerve of this speci- 

 men to their ganglia and the sensory epithelium have so recently been 

 fully discussed by Streeter ^ that they will not be treated. The sensory 

 epithelial thickenings to which he calls attention, are here figured 

 (Fig. 1). 



Beyond the clearly formed folds, above discussed, there occur several 

 others each corresponding with an enlarged part of the ganglionic cord. 

 As this cord has no further indication of dorsal nerve roots, the exact 

 relations cannot be determined. Moreover, the following total folds in 



" Sewertzoff, A. N., Anat. Anz., XXI, 1902. 

 «»Streeter, G. L., Amer. Jour. Anat., IV, 1904. 



