CKANGON VULGARIS. 15 



of a section across the tubular portion of the left posterior 

 liver lobe which shows better the histological structure of 

 the epithelium. The cells are distinctly columnar, and, 

 stained with alum cochineal, the nuclear reticulum shows 

 well. The nucleus occupies about half the cell and the 

 protoplasm outside is slightly granular and stains but 

 slightly though exceeding the nucleus in that respect. The 

 lumen of the follicle is filled with yolk, but the distinction 

 between yolk and cells is not very clearly marked. The 

 inner ends of the cells are irregular and somewhat pseudo- 

 podal in character and the protoplasm in the same region 

 is more granular than that at the opposite end of the cells. 

 This granulation is apparently due to the yolk which is 

 being taken into the cell at this point and is being metabo- 

 lized in an amoeboid manner, much as described by Reich- 

 enbach ('76) in his first paper and by several later authors 

 upon Crustacean development. 



From the foregoing it appears clear that the entoderm 

 cells give rise directly to the so-called liver and that this 

 organ does not arise by diverticula from the main portion 

 of the digestive tract. It would also appear, that in the 

 early stages at least this organ does not really deserve the 

 name of liver, but should rather receive the name given it 

 by Frenzel ('84) of midgut gland ; but as yet it does not 

 fulfil his characterization of it in the adult (p. 99) : "Dass 

 die Mitteldarmdriise [der Crustaceen] die Function einer 

 Verdauungsdriise besitzt, welche in ihrer Wirkung mit dem 

 Pancreas der Wirbelthiere eine grosse Anlichkeit zeigt." 



A difference is to be noted in the development of the 

 liver in Crangon from the process described by Reichen- 

 ]bach ('86) in Astacus, In Crangou all the liver lobes at 

 first lie above the digestive canal ; in Astacus they extend 

 beneath the ingrowing stomodeum and stomach. 



In Palinurus (Dohrn, J 70, 126-127), the liver arises by 



