86 



THE LARVA OF THE B LOW- FLY 



under water. It consists of a median dorsal and two lateral 

 lobes. Sections show that the omentum is much folded and 

 convoluted, that it occupies the greater part of the body-cavity, 

 and has large blood sinuses between its folds. 



The cells of the fat body (Fig. ig,fh) measure about 0*15 mm. 

 in diameter ; they consist of a reticular protoplasm, in the 

 meshes of which granules and globules of fat are imbedded. 

 These are so numerous that they conceal the nucleus. Sections 

 show that the cells are bounded by a thin cuticular membrane. 

 These cells have large vesicular nuclei, which undergo very 

 remarkable changes during the development of the nymph. 



Fig. 17. — Blood corpuscles {leucocytes) of the adult larva : /, living corpuscles, showing 

 the amoeboid condition, in d the nucleus is also amoeboid ; 2, the same, treated 

 with magenta, showing the various appearances produced by the action of the 

 reagent ; j, a living cell in several stages of direct division, all drawn with -fV oil 

 immersion lens. (For details see ' Histology of Tissues.') 



The fat body, although adherent in places to the larger 

 tracheal vessels, has no tracheal capillaries developed on its 

 surface. When removed from the larva and exposed to the 

 air, it rapidly assumes an inky hue, probably the result of 

 oxidisation. The contents of the cells are not easily acted 

 upon by osmic acid, unless the outer wall of the cell is 

 ruptured. 



