164 AN INTRODUCTION TO ENTOMOLOGY 



The lar\^al oenocytes are believed by Verson and Bisson ('91) to be 

 ductless glands which take up, elaborate, and return to the blood 

 definite substances, which may then be taken up by other cells of the 

 body. Other views are held by other writers, but the view given 

 above seems, as this time to be the one best supported by the evidence 

 at hand. 



As to the function of the imaginal oenocytes, there are some obser- 

 vations that seem to show that they are excretory organs without 

 ducts, cells that serve as storehouses for excretory products, becoming 

 more filled with these products with the advancing age of the insect. 



The pericardial cells. — The term fericardial cells is applied to a 

 distinct type of cells that are found on either side of the heart in the 

 pericardial sinus or crowded between the fibers of the pericardial 

 diaphragm. 



These cells can be rendered very conspicuous by injecting ammonia 

 carmine into the living insect some time before killing and dissecting 

 it ; by this method the pericardial cells are stained deeply while the 

 other cells of the body remain uncolored. 



It is believed that the pericardial cells absorb albuminoids origina- 

 ting from the food and transform them into assimilable substances. 



The phagocytic organs. — The term phagocyte is commonly applied 

 to any leucocyte or white blood corpuscle that shows special activity 

 in ingesting and digesting waste and harmful materials, as disinte- 

 grating tissue, bacteria, etc. The action of phagocytes is termed 

 phagocytosis; an excellent example of phagocytosis is the part played 

 by the leucocytes in the breaking down and rebuilding of tissues in the 

 course of the metamorphosis of insects ; this is discussed in the next 

 chapter. 



Phagocytosis may take place in any part of the body bathed by the 

 blood and thus reached by leucocytes. In addition to this widely 

 distributed phagocytosis, it is beheved that in certain insects there are 

 localized masses of cells which perform a similar function; these 

 masses of cells are known as the phagocytic organs. 



Phagocytic organs have been found in many Orthoptera and in 

 earwigs; they are situated in the pericardial region; and can be made 

 conspicuous by injecting a mixture of ammonia carmine and India ink 

 into the body cavity; by this method the pericardial cells are stained 

 red and the phagocytic organs black. 



The light-organs. — The presence of organs for producing light is 

 widely distributed among living forms both animal and vegetable. 



