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KICHARD E. SCAMMON 



part of this pouch is full and rounded and may be termed the pars 

 hepatica mediana. From the median pouch spring two large 

 lateral pouches which form together the pars hepatica lateralis. 

 In stages just preceding the appearance of the tubule anlagen the 

 lateral pouches are smooth and globose and project outward almost 

 at right angles to the median hepatic pouch. At the time when 

 the tubules are formed, however, the lateral pouches are flattened 

 transversely and have entered upon a pronounced dorsal growth. 

 Connected with the liver pouch above and in front and with the 

 anterior wall of the yolk stalk behind is a small thick walled 

 sac, the anlage of the gall bladder. The hepatic tubules take 



Fig. 1 Lateral view of a semi-diagrammatic reconstruction of the foregut 

 and liver of an Acanthias embryo 9 mm. long. The areas represented in stipple 

 give rise to hepatic tubules. 



origin entirely from the pars hepatica mediana and the pars he- 

 patica lateralis. These areas are indicated in stipple in figure 1. 

 The tubule anlagen arise in two forms: as slight longitudinal 

 ridges upon the lower part of the outer surface of the lateral 

 pouches and as very small irregularities of the dorsal margins 

 of the same structures. When first observed the longitudinal 

 ridges are two to four in number on either side. They extend 

 almost the entire length of the lateral pouches and are distinctly 

 separated by shallow lateral furrows. Sometimes these ridges 

 may be subdivided longitudinally at their ends. Figure 17 is a 

 view from the left side and below of the liver of an embryo 7.5 



