238 E. A. BAUMGARTNER 



Left medial ramus. The left medial ramus is joined to the 

 right medial in a 14 mm. embryo (fig. 39). In a 13.5 mm. 

 embryo the left medial is long and divides into dorsal and ven- 

 tral branches (fig. 41). Also in a 15 mm. embryo is the left 

 medial ramus quite long (fig. 42). It divides into medial and 

 lateral branches both of which have dorsal and ventral tubules. 

 The left medial ramus in a 20 nmi. embryo (fig. 43) is joined to 

 the right. The left ventral branch of this combined duct 

 divides shortly into dorsal and ventral radicles. In a 35 mm. 

 embryo (fig. 44) the left hepatic ramus is quite long. Its anas- 

 tomoses with the other rami have been noted. There are also 

 several anastomoses with the left lateral ramus. 



Left lateral ramus. In a 14 mm. embryo the left lateral ramus 

 is very simple, dividing into medial and lateral branches (fig. 40). 

 The left lateral ramus in the next stage shows further develop- 

 ment and growth (fig. 41). In a 15 mm. embryo this ramus has 

 lateral branches given off at quite an angle (fig. 42). It is 

 shorter than the left medial ramus and divides into medial and 

 lateral branches, the latter sending tubules far out to the side. 

 The left lateral ramus in a 20 mm. stage is given off nearly at 

 right angles to the left hepatic duct (fig. 43). It divides into 

 dorso-medial and ventro-lateral branches. In this case the 

 lateral branch is the longer. Several tubules go out laterally 

 almost at right angles and from these tubules hepatic columns 

 go posteriorly as well as anteriorly. In a 35 mm. embryo .(fig. 

 44) the left lateral ramus forms quite a network of ducts. The 

 ventral branch makes an arch forward and is then divided into 

 anterior and posterior branches. In an embryo 45 mm. long the 

 main hepatic ducts are more nearly on the same horizontal plane. 

 Of these ducts the left hepatic has extended farther to the left. 



e. Development of the gall-bladder and cystic duct. The gall- 

 bladder appears somewhat later than the liver as noted by 

 Hammar ('97). It arises as a median ventral outpouching 

 caudal to or in the posterior end of the hepatic anlage. Choron- 

 shitzky has figured the anlage of the bladder in a median, sagit- 

 tal section. The structure is shown as a slight depression de- 

 veloping from the gut, at the entrance of the common duct, and 



