272 
RICHARD E. SCAMMON 
Fig. 5 Minor hepatic duct with connecting hepatic cylinders from the median 
lobe of the liver of an Acanthias embryo 37 mm. long (H.E.C. 353). X 400, 
Lumina of hepatic duct and cylinders solid black; hepatic cells in stippled outline; 
sinusoids, <S, in unbroken outline. 
DEVELOPMENT OF THE HEPATIC MESENCHYMA 
It is well known that the mesenchymal tissue of the selachian 
liver is extremely scanty in the embryo although fairly abund- 
ant around the blood vessels in the adult. No particular study 
has been made of its origin, but Minot ('01) in his study of 
sinusoids, and more recently Debeyre ('09) in following the de- 
velopment of the hepatic cylinders, have noted the occasional 
delamination of mesenchymal cells from the mesothelium cover- 
ing the liver and the presence of such elements along the walls 
of the hepatic sinuses. Debeyre also figures a cross section of a 
small portion of the periphery of the liver of an Acanthias embryo 
30 mm. long, which shows small spurs of mesenchymal tissue 
extending inward from the mesothelium between the hepatic 
