248 RICHARD E. SCAMMON 



Brachet ('95) studying Torpedo embryos determined with 

 accuracy the area of the hepatic diverticulum which gives rise 

 to the hepatic tubules, and confirmed Balfour's description of 

 the structure of the hepatic cylinders in later stages. 



Holm ('97) figured and described very briefly sections of the 

 liver of two Scyllium embryos of advanced stages. 



Most of our later information concerning the embryonic 

 hepatic parenchyma comes from the studies of Braus ('96) on em- 

 bryos of Acanthias, Spinax and Scyllium. Confirming Balfour's 

 observations in regard to early stages he noted a complete and 

 regular anastomosis of the tubules in Acanthias embryos of 38 

 mm. Here the tubules were of even size and consisted in cross 

 section of seven cells surrounding a lumen of variable size but 

 distinctly larger than that seen in the adult. The hepatic cells 

 of this stage were free from fat. In older embryos of Spinax and 

 Acanthias the cells were fat laden. Braus saw no side branches 

 nor blind endings of any hepatic capillaries. 



Choronshitzky ('00) , studying Torpedo, found several secondary 

 hollow outgrowths from the hepatic pouch in his "Stadium II," 

 which corresponds approximately to Balfour's stage K, and to 

 the Normal-plate Nos. 22-24. In "Stadium III" which is 

 represented by considerably older embryos, the liver pouches 

 give rise to a number of small hollow buds, the cavities of which 

 communicate with that of the pouch. "Die Leber macht im 

 allgemeinen den Eindruck einer verzweigten Driise." By "Sta- 

 dium IV" the hollow buds have been transformed into much 

 branched hepatic trabeculae which contain no traces of lumina. 

 Choronshitzky's opinion of the mechanical influence of the blood 

 vessels on the formation of the hepatic tubules will be discussed 

 in a later part of this paper. 



Minot ('00) in discussing the development of sinusoids, men- 

 tions the presence of the first short hepatic cylinders in an Acan- 

 thias embryo of 11.5 mm. and speaks of their anastomosis and 

 growth in older stages. He noted the interesting retardment 

 of development which is to be seen in later stages in the caudal 

 tip of the liver as compared with the cardiac end. 



