Susanna Phelps Clage 439 



upon them indicate the corresponding sections of the series. The following 

 figures have either topographic lines or the section number at which they are 

 cut, and hence can be located with reference to Fig. 1. 



Plate II. 



Fig. 2. A face view of the head. As shown by the topographic lines, it is 

 tilted to give a clear view of the parts about the mouth which is merely a 

 wide slit between the hypophysial region of the head (cf. Figs. 3, 4) and the 

 mandibular process. 



There are seen: The small maxillary process with the depression at the 

 corner of the mouth lying between maxilla and mandible; the H-shape of 

 the nasal epithelium extending also over the cerebral region; the large 

 neuroporic thickening; the lens epithelium with a tract extending along the 

 lachrymal furrow. 



The cut surface (Sec. 125) shows: The division in the dorsal part of the 

 auricles (cf. Fig. 3); the entrance of the sinus venosus into the right part 

 (left of Fig.); the liver lying in the septum transversum; the folds about 

 the duct of Cuvier, pushing across the space to help form the diaphragm; 

 the connection of pericardial and abdominal coelom; the opening of the lesser 

 peritoneal cavity into the abdominal coelom. 



Fig. 3. A view from the left side showing the central nervous system, 

 pharynx, heart, lung, and liver. The lateral wall has been removed. Pro- 

 jections of the ear vesicle and myotomes 1-15 are indicated by dotted out- 

 lines. 



The approximately uniform tube formed by the central nervous system 

 and the strong cephalic flexure characteristic of this stage of development 

 are evident. The mesoderm in the flexure has been removed. 



The brain shows: The series of total folds; the great prominence of the 

 albicantial; the relation of the neuropore to the epidermis and to the visual 

 lobe or eye; the small size of the striatal, olfactory, and cerebral folds; the 

 relation of the fold, oblongata 2, to the Vth nerve root (shown by a dotted 

 circle); of the fold, obi. 4, to the Vllth and Vlllth nerves (dotted circles); 

 of fold, obi. 6 to N. IX; the great size of fold, obi. 7 and its relation to 

 N. X; the continuity and segmented character of the ganglionic chain in 

 the neck region with the roots of the Xlth nerve extending along its dorsal 

 side; and the folds in the myel. 



There are seen: The inner tube of the bulbus arteriosus as it enters the 

 floor of the pharynx and divides into the aortic arches; the median thyroid 

 cephalad of this branching; lateral folds just cephalad of the thyroid, the 

 only rudiments of the tongue present; the bursa pharyngea, the dorsal pocket 

 at the division of trachea and esophagus (at left of abbreviation ch.) ; dotted 

 lines indicating the outline of the epithelial tubes forming lung and alimen- 

 tary canal; the wide communication of the pericardial and abdominal coelom 

 dorsad of the septum transversum; the point of union of the aortse (aorta); 

 the hypophysis cut to the left of the middle line. 



Fig. 4. A mesal view of the brain, myel, and pharynx. The brain shows 

 from the interior the same total folds as Fig. 3, but brings out somewhat 

 more clearly the grouping of folds into lobules (cf. Table II, in the text). 

 The elevations in Fig. 3 correspond to the depressions in Fig. 4. 

 34 



