THE INTERNAL STRUCTURE OF ANTS. 39 



appear, but the gutter, reduced to a simple depression of the wall, is 

 continued very distinctly to the slit which forms the opening of the 

 chamber. This latter is always filled with air." In Lasins flatus " the 

 chamber is widely open to the exterior and the grooves of its walls are 

 absent and replaced by hairs." In one of his preparations Janet found 

 that " these hairs are inserted inside the chamber around the cribellum 

 and converge in such a way as to appear like a pointed, hollow brush, 

 i. e., one reduced to the hairs that form its external surface. This 

 pencil recalls the trichodes of myrmecophilous beetles (see Chapter 

 XXII ). In Formica nifa the chamber is much reduced and opens 

 more widely to the exterior than in Lasins flarus. The cribellum is 

 beset with hairs which form a brush long enough to project outside 

 the chamber. The glands of the sixth abdominal segment consist of 

 two small clusters of cells whose ducts open on the dorsal interseg- 

 mental membrane just in front of the rigid chitinous border of the 

 seventh segment. The metatarsal gland is situated in the fore-leg at 

 the base of the tarsal comb of the strigil. 



The Reproductive Organs. In the female, or queen ant, the repro- 

 ductive organs comprise the two ovaries, each of which consists of a 

 number of tubes, or ovarioles, in which the elliptical eggs are formed 

 in a single series, very small at the distal or anterior and gradually 

 increasing in size towards the proximal or posterior end of the tube. 

 Each egg is surrounded by a follicular epithelium, which secretes from 

 its inner surface the thin, transparent chorion enveloping the ripe egg, 

 and is accompanied by a cluster of nurse cells. The ovarioles, which are 

 bound together in a fascicle by richly ramifying tracheae, are attached 

 at their tapering anterior ends to the pericardium in the antero-dorsal 

 region of the gaster ( Fig. 15, ot ). The number of ovarioles in each ovary 

 varies considerably in the queens cf different ants. Miss Bickford ( 1895 ) 

 gives the following numbers for several European species: Formica ntfa 

 45, F. rufibarbis 18-20, Lasins nigcr 30-40, L. flams 24, L. brnnncus 

 O-i i, Cainponotus 39-40, Alynnica rnginodis 8, M. lei'hwdis 12, AI. 

 scabriuodis 8-9, M. snlcinodis 9-11, Ancryatcs atratnlns 12, Plagiolepis 

 pygmcca 4-5; and Miss Holliday (1903) finds the following numbers 

 in several American ants: Pachycondyla harpa.v 5-7. Odontomachus 

 darns 5, Eciton sclimitti about 250, Leptothorax emersoni 2, Cremasto- 

 gastcr minntissiuia 2, Colobopsis ctiolata 6-7, Camponotns dccipicns 

 12, C. festinatns 15-18, C. sansabeanns 6-17, Pogonomyrmex nwle- 

 faciens 25-30. The ovarioles of each ovary unite at their posterior 

 ends to form a short oviduct, and the two oviducts in turn unite to form 

 the uterus, which bears on its dorsal surface a small subspherical pocket, 

 the seminal receptacle, which is filled with sperm by the male during 



