DEVELOPMENT OF THE ELASMOBRANCH LIVER 



385 



is much reduced in diameter between the time when it is first 

 formed and when it begins it growth backward along the base of 

 the valvular intestine. After this phase begins there is but little 

 change in caliber. In the intrahepatic and preduodenal regions 

 the duct is circular in trans-se.ction, posteriorly it is flattened 

 transversely until elongately oval in trans-section. 



Table 2 shows numerically the growth of the duct and the chang- 

 ing relations of its ostium. Some error is doubtless introduced in 

 the calculation of the length of the duct from cross sections as is 

 done here, but Acanthias embryos of 18 mm. and over shrink 

 comparatively little in imbedding and that shrinkage seems to be 

 symmetrical so that the value of the figures is not seriously im- 

 paired. The 'extra-hepatic length' is taken from the point where 

 the duct turns sharply downward immediately after leaving the 

 liver to the point where its lumen becomes continuous with that 

 of the gut. It is not possible to determine this point exactly in 

 specimens under 20 mm, in length so only the total length of the 

 duct has been given in such cases. 



TABLE 2 

 Growth and relations of the ductus choledochus 



