ANTS. 



attached to the suspensory filaments and aliform muscles. In the living 

 insect these cells have an acid reaction. They probably function as 

 ductless glands, taking certain substances from the blood, transforming 

 them and returning them to the circulation in such a form that they 

 can be absorbed and excreted by the Malpighian vessels (Cuenot). 

 Some authors are of the opinion that these pericardial cells also give 

 rise to the amoebocytes. that they constitute, in other words, a hasmato- 

 poetic organ. The oenocytes are glandular cells which arise in seg- 

 mental clusters from the ectoderm of the embryo just behind the tracheal 

 invaginations. In the ants these cells are very small and in the adult 

 'scattered about among the fat cells. They are very conspicuous in the 

 young larva and still occupy their embryonic position, but in aged ants, 

 according to Janet, they disappear. Like the pericardial cells they are 

 probably ductless glands, producing some unknown but physiologically 

 important internal secretion. The fat cells form large masses or packets, 

 often filling out all the spaces of the body cavitv between the viscera, 

 especially during the larval and pupal stages. As the name indicates, 



,-d 



FIG. 25. Longitudinal sections to show valve and method of closing the tracheae 

 in Myrmica ritbra. (Janet.) A. Last abdominal trachea open : B. closed; o. stigmatic 

 orifice: (7, anterior stigmatic chamber; b, occluding chamber; c. fixed insertion of 

 occluding muscle ; d. mobile insertion of same ; e, mobile insertion of opening muscle ; 

 /, occluding muscle; g. opening muscle; /;, stiffened portion of trachea; i, stigmatic 

 or main tracheal trunk. 



these cells have their cytoplasm filled with fat globules, which are often 

 so numerous that the nucleus is reduced to a stellate or irregular body. 

 Unlike the oenocytes, the fat cells are of mesodermal origin. Theurate 

 cells are found singly or in clusters among the fat cells. They are 

 large and opaque, owing to a mass of urate crystals stored in their 

 cytoplasm. They are most easily seen in larvae and pupae and may be 

 regarded as a very primitive form of kidney adapted for storing instead 

 of excreting the products of tissue metabolism. 



