NITROGENOUS EXCRETION 57 



(1942 a, b) has much interesting work on the nutritive functions of 

 chloragogen which is deah with in the section on regeneration. 



The presence of food substances such as glycogen and fat has 

 been reported at intervals since early this century, but the most 

 exhaustive study made so far is that of van Gansen (1956). The 

 most important food reserve, if bulk be the criterion, is glycogen. 

 In fresh feeding A. caliginosa a concentration of 62-3 jLtg/mg dry 

 wt. of intestine is obtained, a quantity which decreases drastically 

 to 33-6 jLtg/mg dry wt. after the animals have been starved for one 

 month. Lipid substances, also possible energy stores, are found in 

 two forms, lipids and fats, the former remaining unaffected by 

 starvation, the latter being depleted. Alkaline phosphatase, an 

 enzyme often found in rapidly metabolizing tissue, is not present, its 

 place being taken by an acid phosphatase. The probability that the 

 materials within the chloragocytes originate in the intestinal wall 

 is suggested by the occurrence of large concentrations of alkaline 

 phosphatase in the distal ends of the intestinal cells lying alongside 

 the chloragocytes, indicating the active transport of absorbed 

 substances across the cell boundaries of this region. 



The chloragocytes contain many obvious granules. Those at the 

 periphery of the cells stain intensively with Sudan black and histo- 

 chemical methods (PAS, PFAS tests) show that phospholipids are 

 present, and contain ethylene groups. The typical brown-yellow 

 colour of the chloragocytes is imparted by a chromolipid, the 

 alimentary origin of which is not immediately apparent, but which 

 is possibly an oxidized phospholipid which polymerizes with 

 purines within the cell (van Gansen, 1957b). Roots (1960) has 

 discussed this chromolipid and shown that it consists of a phospho- 

 lipid allied with a yellow-brown spectrally uncharacterized material 

 which she thinks may indicate that the pigment is a very complex 

 mixture of substances in equilibrium. Other inclusions within 

 chloragocytes include mineral aggregates, identified in electron 

 microscope and X-ray diffraction studies as muscovite or mica 

 (van Gansen and van der Meersche, 1958). Roots (1960) finds that 

 not all the inorganic ash of the cells is due to silica and believes that 

 where this substance is present it is due to accidental penetration 

 from the lumen of the gut. The siliceous granules are not to be 

 found universally in the chloragogen. 



The facts mentioned above are all in support of the theory that 



