334 RICHARD E. SCAMMON 



The present paper, based upon a study of an extensive series of 

 embryos of Squalus acanthias' gives an account of the early 

 development of the Hver and the history of the principal liver 

 ducts and the gall bladder. In a later section it is hoped to 

 give an account of the development of the smaller rami of these 

 ducts and of the hepatic parenchyma. 



ir. LITERATURE 



At this point I shall review only briefly the literature of the 

 general development of the elasmobranch liver. Particular 

 points are considered in more detail in the separate sections and 

 reviews of the literature by Brachet ('97), Choronschitzky ('00), 

 Piper ('02), and Weber ('03) already cover a part of the subject. 



In common with so many points in selachian embryology 

 there was but little knowledge of the development of the liver 

 until the researches of Francis Balfour. Rathke ('27) published 

 an account of several selachian embryos including one of Squalus 

 mustelus (Mustelus canis?) of an approximate length of 45 mm., 

 in which he described the division of the liver into an anterior 

 mass and two posterior lobes and traced the course of the ductus 

 choledochus to the intestine. He stated that the gall bladder 

 was absent in this specimen as well as in an older one of Squalus 

 canicula (Scyllium canicula?). At such a stage this structure is, 

 in fact, embedded in the liver substance and not visible exter- 

 nally. Rathke observed the gall bladder however in an embryo of 

 Squalus mustelus 7 inches 2 lines in length, and traced the course 

 of the vitelline veins to the liver and followed their ramifications 

 in this organ to their final connections with the sinus venosus. 



Franz Leydig ('52) in his "Beitrage zur microskopischen 

 Anatomie und Entwicklungsgeschichte der Rochen und Hai" 



1 This material consisted of sectioned embryos of Squalus acanthias from 3 to 

 86 mm. in length as well as several specimens of the same species in the 'pup' 

 stage, and a few large embryos of Mustelus laevis and Squalus sucklii (?). In a 

 large part these specimens were from the Harvard Embryological Collection, 

 and I wish to express here my thanks to Dr. Charles S. Minot for their use for a 

 prolonged period, as well as for the privileges of his laboratory during a part of 

 the time while this study was in progress. Four specimens were also from the 

 embryological collection of the University of Kansas. For their use I am indebted 

 to Dr. C. E. McClung. 



