DIGESTIVE SYSTEM OF THE LOBSTER 169 



through is distributed in the various diverticula of the hepato- 

 pancreas where the bulk of digestion takes place. Here also 

 are the absorbing cells which take up the digested foods and 

 turn them over to the blood. The end gut or intestine plays 

 no role either in digestion or in absorption. The absorption 

 cells have the same general structure as those of the earthworm. 

 The connective tissue in which the hepato-pancreas is embedded 

 is richly supplied with blood vessels and lymph spaces which 

 probably receive digested food directly from the absorption 

 cells. 



The digestive fluid which comes from the hepato-pancreas is 

 very complex. It is of yellowish-brown color, not viscous, is 

 rich in albumen, contains a free alkali and gives a flocculent 

 precipitate with acids. This precipitate, filtered and washed, 

 gives all of the reactions of a globulin. The digestive ferments 

 contained in this juice are (i) a protease or proteolytic ferment 

 similar to the proteid digestive ferments of the earthworm and 

 other invertebrates; (2) a lipase or fat emulsifying ferment; (3) 

 an amylase or starch converting ferment. In other allied forms 

 of Crustacea still more ferments have been obtained from the 

 digestive juices and which may be present in the lobster. Thus 

 a cellulose dissolving ferment (cytase)was discovered by Bieder- 

 mann and Moritz from the crayfish. 



The digestive tract of the lobster thus shows a considerable 

 advance over that of the earthworm or other lower types. The 

 functional digestive part is removed from the main tract but is 

 derived from it as an outgrowth or diver ticulum. It represents 

 a step toward still higher types of development where secretions 

 from different glands are poured into a digestive sac or stomach 

 and intestine. Here in the lobster the digestive gland still acts 

 as a part of the glandular tube of a worm, the food is contained 

 in it and digestion and absorption take place in it instead of in 

 the main digestive tube. In higher animals all of the glands 

 pour their digestive fluids into the main tube. 



The Blood Vascular System. In the lobster and other forms 

 of arthropods all of the blood of the organism passes sooner or 

 later from the main arteries into the general cavity of the body 



