294 RICHARD E. SCAMMON 



In Acanthias the establishment of the sinusoidal circulation 

 and the process of anastomosis of the hepatic tubules occur 

 almost simultaneously. In Mustelus and Torpedo the hepatic 

 tubules anastomose immediately after their intercresence with 

 the omphalo-mesenteric veins. At first sight there would seem 

 to be some relation between the sinusoidal type of circulation 

 and the anastomosis of glandular end-pieces. This seems to be 

 supported by the evidence that the pancreas of ganoids has free 

 anastomoses with a sinusoidal circulation and these conditions 

 are also found in the paraphysis of Necturus (Warren '05) and 

 in the islands of Langerhans in Mammalia (deWitt '06). Sinus- 

 oids also occur in other ductless glands which anastomose. 

 On the other hand I have found no report of anastomoses between 

 the tubules of the mesonephros, and a free sinousoidal circulation 

 exists in this organ. The tubules of the embryonic mammalian 

 pancreas are known to anastomose freely, and there is no record 

 of a sinusoidal circulation in this organ. Similarly Braus ('00) 

 finds a free anastomosis of the end pieces of the bulbo-urethral 

 gland which has the capillary type of circulation and Bremer 

 ('11) has found the same conditions in the testis." It is evident 

 that no general rule can be laid down regarding this relation, at 

 least with our present knowledge of the subject. 



SITMAIARY 



A. Development of the hepatic parenchyma 



1. Hepatic tubules are first represented by longitudinal ridges 

 formed on the external surfaces of the pars hepatica lateralis 

 and medialis, and by slight irregularities of the margins of the 

 pouches forming the pars hepatica lateralis. 



2. The hepatic ridges are converted into irregular rows of 

 tubule anlagen by transverse constructions. 



3. The individual tubule anlagen thus formed grow outward 

 and are differentiated into expanded terminal chambers and 



" Occasional anastomoses are found in a number of glands such as the gastric 

 and uterine glands. It is to be expected that such occasional connections will 

 be found in almost any gland which is studied carefully with the aid of recon- 

 structions. 



