THE INTERNAL STRUCTURE OF ANTS. 4 1 



crowded with cysts containing mature sperm, or testicular cells in 

 various stages of spermatogenesis (sp), unite in each testis to form a 



FIG. 20. Poison apparatus of Formica. A, Lateral and slightly dorsal aspect of 

 apparatus in Formica rufibarbis. (Forel.) a, Duct of poison vesicle, or reservoir: b. 

 cushion formed by the long convoluted portion of the duct from the two free glandular 

 tubes (c) ; d, tracheae: e, ring-muscles of vesicle wall: /, nerves; g, intima of vesicle; 

 /i, accessory gland; i. its orifice; in. gland-cells of its walls; n. muscles; o. sting- 

 sheath ; />. vestigial sting-groove ; r, somewhat dislocated, vestigial right sting-stylet : 

 s, piece of the cloacal membrane which has been almost entirely removed. B. Trans- 

 verse section through poison apparatus of Formica rufa. (Beyer.) w. Dorsal wall of 

 vesicle ; .r, sections of convoluted duct forming the cushion-shaped mass ; v, opening 

 of duct into the vesicle, the lining of which is represented by the more heavily 

 shaded layer (s). 



