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E. A. BAUMGARTNER 



evagination has developed into quite a ridge separating the gall- 

 bladder from the developing hepatic ducts. On the ventral 

 surface the anterior furrow separating liver and gall-bladder 

 from yolk-mass is, as before, the more marked. 



According to Shore ('91) in the frog the furrows found in the 

 liver-mass are caused by the 'tunnelling in' of blood vessels. 

 That it is not due only to this is apparent in Amblystoma where 

 sections of this and other embryos show furrows in which there 

 are no blood-vessels (fig. 4). It is important to note that Shore 

 saw no vascular endothelium in these spaces which he regarded 

 as blood-vessels. 



Fig. 4 Sagittal section of an embryo almost 9 mm. long. X 30. Dhd., 

 ductus choledochus; F.g., foregut; G.B., gall-bladder; He, heart; Li., liver ; Lu., 

 lung; Y, yolk mass. 



In another embryo of 9 mm. in length the liver in cross sec- 

 tion (fig. 5) appears as a large oval mass with an irregular surface 

 showing deep furrows separating the developing ducts. There is 

 also a very marked dorso-ventral furrow separating the liver- 

 mass into two unequal lateral portions of which the left is the 

 smaller. The right portion is marked by two lesser furrows, 

 one ventral, the other lateral. 



In 10 mm. embryos a beginning of the network of anastomos- 

 ing trabeculae can be seen. The development of the sinusoidal 



