LABRAL GLANDS OF STMOCEPHALUS 2B8 



gland-cell ; nu.a.d. nucleus of cell of anterior pair of distal gland-cells ; 

 nu.p.d. nucleus of cell of posterior pair of distal gland-cells ; nu.d.c. nucleus 

 of duct-cell ; oe, oesophagus ; o.g. olfactory ganglion ; p.c. peripheral 

 layer of cytoplasm of anterior pair of distal gland-cells ; r, reservoir of 

 secretion ; s.m. setae of maxiUa ; ?', vacuoles of secretion. 



Figs. 1-8 form a series of transverse sections through the la brum and 

 adjacent parts of an adult specimen of Simocephalus vetulus. 

 The position of these sections is indicated in fig. 13 by the series of vertical 

 lines numbered 1-8 at their upper ends. Figs. 9, 10, and 11, are drawings 

 at a higher magnification of parts of the same sections that are represented 

 in figs. 3, 5, and 6 respectively. The orientation of figs. 9-1 1 with respect 

 to the plate is the same as it is in figs. 3, 5, and 6. In figs. 1-8 and in 

 fig. 13 the proximal glands are shaded thus ////////////// and the distal 

 glands are shaded thus WWWWWWW. 



Fig. 1. — Section cutting the most anterior part of the proximal gland 

 at the level of the nerve to the first antenna. 



Fig. 2. — Section through anterior end of the distal gland. This section 

 passes through the nerve to the proximal gland. 



Fig. 3, — Section through the connexion between the proximal and 

 distal groups of gland-cells. 



Fig. 4. — Section through the attenuated connexion between the anterior 

 and posterior pairs of gland-cells of the distal gland. This section passes 

 through the commencement of one of the mandibles and includes the 

 labral nerve-loop. 



Fig. 5. — Section through the posterior pair of cells of the distal gland. 

 This section includes the tips of the hairs on the setae of the maxillae. 



Fig. 6. — Section through the duct-cell. 



Fig. 7. — Section through the external opening of the duct of the labral 

 gland. 



Fig. 8. — Section through the maxillae and the tip of the lalirum. 



Fig. 9.— See fig. 3. 



Fig. 10.— See fig. 5. 



Fig. 11.— See fig. 6. 



Fig. 12. — Horizontal section, the position of which is indicated in fig. 13. 

 It passes through the aperture of the duct of the labral gland. 



Fig. 13. — Somewhat diagrammatic figure of a side view of Simo- 

 cephalus vetulus. Of the appendages behind the antennae only the 

 right mandible and maxilla are represented. 



