932 THE AMERICAN NATURALIST. [Vor. XXXIV. 
embryo to the pelvis, where it forks to form the two allantoic 
arteries, which run to the umbilicus, and entering the umbili- 
cal cord supply the extra-embryonic or placental circulation. 
The aorta is surrounded by mesenchyma, and to this are, so to 
speak, appended the large Wolffian bodies (W.4.), one on 
each side. They are much larger, relatively to other parts, in 
the pig than in man or the rabbit. The Wolffian body is 
the fetal or embryonic kidney, and is also termed the meso- 
nephros. It consists of numerous epithelial tubules (W.t.), 
very much contorted, with blood spaces (sinusoids) between 
them, and of glomeruli, which always lie towards the median 
and inferior side of the organ. All of the tubules open into 
the single longitudinal canal, the Wolffian duct. This duct 
is always situated close to the surface on the ventral side of 
the organ, and is very easily distinguished in dissected em- 
bryos after the removal of the intestines and liver. In the 
figure it may be easily found in the left mesonephros (JJ. .), 
it being thére the lowermost of the cavities drawn. On the 
median lower surface of the Wolffian body, underneath the 
glomeruli, is an accumulation of tissue (Gez.), the anlage 
of the genital gland. Below the aorta, on the right of the 
embryo, is the large ductus venosus, or upper end of the vena 
cava inferior, on its way past the right dorsal lobe of the liver 
towards the heart. Below the aorta on the left is the meso- 
gastrium (Om.maj.), or future great omentum, by which the 
stomach is suspended from the median dorsal wall of the abdo- 
men. The stomach (Sz.) is entirely upon the left side of the 
body, and is directly connected by means of the anlage of the 
lesser omentum (Om.min.) with the liver. The liver is by far 
the largest organ of the body; it takes up nearly half of the 
section. It is divided into four main lobes, two dorsal and 
two ventral, two on the right and two on the left. The ref- 
erence line (Z7.) runs to the left dorsal lobe. The liver con- 
sists of a complicated network of relatively large blood sinu- 
soids, the spaces between which are occupied by the embryonic 
liver cells. Near the median line between the ventral lobes 
appears the gall-bladder (G.4/.), which is cut three times. The 
liver is attached in the median ventral line to the body-wall 
