336 RICHARD E. SCAMMON 



In a later paper of a more general nature on the early develop- 

 ments of the liver, Hammar ('97) expresses his views in regard 

 to the origin of the selachian liver as follows: 



Bei den Selaehiern wird ebcnfalls eine unter dcm Herzen hervorra- 

 gende stufenahnlu^ho Lel;)erfalte gcbikk^t, an deren cranialen Rand schon 

 friihzeitig zivei hilateral-syminetrische Divertikel auftreten — Zwischen 

 diesen beiden Divertikeln und beinahe gleichzeitig mit ihnon entsteht 

 als eine craniovontrale Verlangerung der Leberfalte noch ein drittes 

 mediancs Divertikel, aus welchen die Gallenblase und Gallenblasengang 

 hervorgehn.' 



I quote Hammar at length for he holds a view somewhat differ- 

 ent from that accepted by most investigators and one which this 

 paper will in part confirm. 



Laguesse ('94) gave a brief account of the development of the 

 liver in Squalus acanthias in connection with his study of the 

 pancreas in this form. He states that the liver arises a little 

 later than the pancreas, a point which has since been disproven, 

 and although in possession of younger embryos, he apparently 

 first observed the organ in an embryo 8 mm. in length, where it 

 appeared as a thick walled ventral pouch extending from the 

 primitive sinus venosus to the anterior wall of the yolk-stalk. 

 An embryo of 9 mm. length showed the formation of the lateral 

 diverticula. At 16 mm. the buds of the hepatic tubules had 

 appeared and at 19 mm. they were fused together, forming the 

 typical net-work of hepatic trabeculae so often described. La- 

 guesse emphasizes the late appearance of the gall bladder as a 

 structure distinctly separated from the hepatic anlage proper. 

 This seems to me to be a point of much importance which 

 apparently has not been recognized by other workers in this field, 

 with the exception perhaps of Hammar. 



lirachet ('96) devoted the first part of his contribution to the 

 development of the liver and pancreas to the selachian liver as 

 represented by Torpedo ocellata. Like Hammar he presented a 

 series of reconstructions corresponding to Balfour's stages J, K 

 and L. The two main points in this paper consist of, first, an 

 affirmation of Balfour's statement that the liver arises between 



-' Tho italics are the author's. 



