366 



RICHARD E. SCAMMON 



rami and graduall}^ enlarging this space presses the tubules apart 

 until it forms one of the larger channels of the vein. 



The right omphalo-mesenteric vein, after establishing its pos- 

 terior connection with the subintestinal vein, which it does when 

 the embryo reaches a length of about 10 mm., grows rapidly, 

 although it never equals in size that of the opposite side, and does 



Pduchmcd. 

 D.cyst. 



R.hep.p 



Fig. 18 Transverse section of iin Acanthias embryo, 1.5.5 mm. long (S.C. 1). 

 X 100. D.cy.st., cystic duct. G.bl., gall bladder; P.duct.med., pars ductus medi- 

 ana; R.hep.p., right hepatic pouch; S., sinusoids of right omiihalo-mescntenc 

 vein; St., stomach; V.omph.l., left omphalo-mesenteric vein. 



not affect the position of the biliary apparatus to any great degree. 

 At first the right and left omphalo-mesenteric veins pass forward 

 to meet in front of the anterior portion of the median hepatic 

 pouch but in later stages the vessels become confluent behind 

 and below the anterior part of the median hepatic pouch or its 

 derivative, thus forming a large sinus which increases the effect 

 already begun by j;,he left vitelline vein, viz., shifting the common 



