EXTERNAL FORM OF EMBRYO OF 15 MM. 



225 



in a nearly straight line from limb to limb, marks the ventral edge of the large 

 Wolffian body, or mesonephros, the dorsal limit of which is approximately indicated 

 by the milk-line, M.L. The outlines of the smaller left dorsal lobe of the liver 

 are distinct, and map out a pointed area immediately below the fore limb, A.L. 

 Above the diaphragm lies the protuberant cardiac region, the outlines of which pass 

 from the umbilical cord below the nasal and pharyngeal regions toward the cer- 

 vical sinus. The long tapering tail extends alongside the umbilical cord. 



FIG. 167. PIG EMBRYO OF 15 MM. X 8 diams. 



Pig Embryo of 15 mm. (Fig. 167). As compared with figure 166, the present 

 embryo (Fig. 167) has not only grown in all its dimensions, but has also changed 

 in form. Unlike the embryo proper, the umbilical cord has grown very little. We 

 notice at once that the outline of the back is less curved than before, that the ventral 

 side of the body has acquired a convex outline, and that the head has become 

 considerably larger, both absolutely and relatively to the body of the embryo, and 



