THE FAT BODY AND THE (ENOCYTES. 121 



first small and increase about five times in diameter before reaching 

 their adult proportions. The fat cells and the oenocytes, although 

 closely associated with each other, are easily distinguishable by their 

 size and by their reaction in life to staining solutions. Koschevnikov 

 fed some bees hone}^ or sugar sirup containing sesciuichlorate of iron 

 and then, after a few hours, removed the fat body, washed it in ferro- 

 cyanide of potassium, and placed it in alcohol acidulated with hydro- 

 chloric acid. He found a precipitate of Berlin blue in the fat cells 

 while the oenocytes remained perfectly colorless. Thus he showed 

 conclusively that the two classes of cells are physiologically different 

 in life, although, he says, if a piece of dissected fat body be placed 

 in the staining solution the color diffuses alike throughout all the 

 cells. 



The oenocytes have a golden brown pigmentation but no differen- 

 tiated contents in young workers and queens. In old workers, to- 

 ward the end of the summer, yellow granules begin to appear in 

 them. During winter and especially in early spring the oenocytes 

 of the workers contain a great number of these granules, but they are 

 present in greatest quantity in queens several years old, wdiile in the 

 latter the fat cells also contain similar granules. Although 

 Koschevnikov admits that the chemistry of these granules is entirely 

 unknown, he thinks that they are undoubtedly excretory substances, 

 that the waste products of metabolism are first taken up by the oeno- 

 cytes and then delivered to the blood, and that the accumulation of 

 the granules in the cells during old age means the loss of power 

 to discharge them, which brings on the decline in the life activity of 

 the bee. If this is so, then the oenocytes are, as he states, excretory 

 organs without ducts — cells which serve as depositories for waste 

 products. 



According to this theory of Koschevnikov, the oenocytes might be 

 likened in function to the liver of vertebrate animals, which, accord- 

 ing to the present views of physiologists, is the seat of the splitting 

 up of the immediate nitrogenous products of katabolism, discharged 

 into the blood from the tissues, into those final compounds of nitro- 

 gen excreted by the kidneys. 



AMieeler" also describes the fat cells and oenocytes of insects 

 as perfectly distinct in their origins, the fat cells arising from the 

 mesoderm, which is the embryonic cell layer between that which 

 forms the outer body wall and that which forms the embryonic ali- 

 mentary canal, while the oenocytes are derived from internal pro- 

 liferations of ectodermal cells. 



"Couceriiins the Blood Tissue of Insects. Psyche, VI, isn2, pp. 216-220, 

 233-230, 253-258, PI. VII. 



