200 PROCEEDINGS : BOSTON SOCIETY NATUR AL HISTORY. 
compared with the cardiac end can be seen in a single sagittal 
section, for example in an embryo of 37 mm., the oldest at my dis¬ 
posal, Harvard Coll., No. 176, sections 1*24-130. 
As regards the liver of the chick, it seems to me that compara¬ 
tively little has been added to our knowledge, since the publication 
of Remak’s admirable observations, ’50.1, pp. 51-53. The follow¬ 
ing summary indicates the approximate ages at which the principal 
stages may be observed. 
Fig. 7. Embryo chick of six days, 12.0 mm. Section of the liver; h. c., 
hepatic cylinder; Si, sinusoid. Harvard Embryologieal Collection No. 258. 
45-50 hours: 
55-60 hours: 
60-90 hours: 
90-98 hours.: 
anlage of the hepatic diverticula. 
outgrowth of the two hepatic diverticula; beginning 
of the solid hepatic cylinders. 
the still solid hepatic cylinders have formed anasto¬ 
moses ; sinusoids occupy the spaces between the cyl¬ 
inders and communicate freely with the subintestinal 
vein. 
the lumina of the hepatic cylinders begin to form, 
F. Frobeen, 92.1. 
