Susanna Phelps Gage 441 



The heart (Sec. 168) cut near its middle shows: The undivided chamber of 

 the ventricle; a strong fold arising between the two sides and separating 

 the exit of the bulbus arteriosus (cf. Fig. 12) from the entrance of the 

 auriculo-ventricular canal (cf. Fig. 10). 



Fig. 7. From a segment of the model cut at section 200, near the edge 

 of the neuropore, looking into the roof of the curved brain tube and showing 

 that the striatal, olfactory, and cerebral folds, and those of the roof of the 

 diencephal and of the mesencephal, meet in the mid-dorsal line, there being 

 no division by a middle partition. 



Fig. 8. A segment of the model extending from Sec. 198 to 155. It cuts 

 the neuropore (cf. Fig. 16), showing a pit on its neural aspect, and looks 

 into the visual lobe and eye vesicles in the opposite direction from Fig. 7. 

 It shows the notch at the tip of the optic vesicle, apparently the beginning 

 of the optic cup. 



The deep projection of the floor of the mesencephal into the albicantial 

 region is here shown and the independence of the albicantial folds from those 

 dorsad of it (cf. Fig. 9). 



Plate IV. 



Fig. 9. A segment of the model from section 162 to section 200 (cf. Figs. 

 1-4), showing: A caudal view of the eye vesicle and visual lobe; the V-shaped 

 union of the albicantial folds and their independent dorsal ending; the 

 mesencephal with its sharpened beak-like ventral ending between the albi- 

 cantial folds; the strand of tissue, at the point where the III N. would later 

 appear; the hypophysis forming a bi-lobed, ectodermic organ surrounding the 

 end of the hypophysial fold; part of the neuroporic thickening; and the Gas- 

 serian ganglion. 



Fig. 10. A segment of the model extending from Sec. 155, through the 

 cephalic flexure, to Sec. 9G. With dissections at Sees. 130 and 140. It shows: 

 The base of the mesencephal and oblongata, with the large protuberance (4) 

 at the end of the second total fold of the mesencephal; the oblongata folds 

 1-5, and the relations to the Vth and Vllth Ns.; mouth; pharynx; the ending 

 of the gill-clefts 2-4 in the precervical sinus; the entrance of the vitelline 

 veins into the liver at the side of the duodenum and their union in the 

 dorsal part of the liver with the sinus venosus; the vitelline artery; and 

 the mesonephros. 



Fig. 11. A view from the dorsal side of the same segment of the model 

 as is shown from the ventral side in Fig. 10, i. e., it extends from Sec. 96 to 

 Sec. 155 (cf. Figs. 1, 3, 4). It cuts the arm buds, looks into the floor of the 

 pharynx and cephalad into the pons, mesencephal and ear vesicles. 



There are seen: A portion of the cerebellum with its folds; the mesen- 

 cephal with its narrow opening cephalad and its floor protruding deeply into 

 the pons region; the interior view of the pons lobule with its three folds, 

 obi. 1, obi. 2, obi. 3; the otic lobe showing the ventral ends of folds, obi. 4, 5; 

 obi. 4 connected with the Vllth and Vlllth nerve; at the right the relation 

 of the ear vesicle to obi. 5; at the left the ganglion of the Vlllth lying next 

 the otic vesicle, that of the Vllth crossing dorsad of the first gill-pouch; at 

 the right the intimate union with the epidermis of the ganglion of the IXth 

 nerve; the ventral ends of folds obi. 6. 



