446 C. GORDON HEWITT. 



to viii, V. Fifth to eighth ventral plates or arches, sn.p. The suranal plate 

 (ninth dorsal arch). 



Tiie anus is situated between the two lateral terminal tubercles. 



Fig. 9. — Dorsal view of the penis and the ventral half of the terminal 

 abdominal segments. The median portion of the eighth dorsal arch has been 

 removed, leaving the lateral portions attached to the body of the penis {c.pe.) 

 and the ventral arch of the seventh segment (vii, v.). 



Lettering as in Tig. 10. 



Pig. 10. — The posterior end of the abdomen of the male seen from behind, 

 showing the pronounced sinistral asymmetry. 



V, d. to viii, d. Fifth to eighth dorsal plates or arches, v, v. to viii, v. Fifth 

 to eighth ventral plates or arches. a7i. Anus. g.a. Aperture of genital 

 atrium, p.f. Primary forceps. 



PLATE 24. 



Fig. 11. — Nervous system. The very Cne nerve which runs along the 

 dorsal side of the oesophagus to the proventricular ganglion {Pv.g., Fig. 20) 

 has been purposely omitted. 



ab.n. Abdominal nerve, ac.ms. Accessory mesothoracic dorsal nerve, acini. 

 Accessory metathoracic dorsal nerve, cer.n. Cervical nerves, en. Cephalo- 

 thoracic nerve cord. O.V. Optic peduncle. pr.cr.,ms.cr.,mt.cr. Pro-, nieso-, 

 and meta-tlioracic crural nerves, pr.d., ws.d., mt.d. Pro-, meso-, and meta- 

 thoracic dorsal nerves. 



Fig. 12. — Thoracic compound ganglia. Left aspect. 

 Lettering as in Figs. 11 and 14. 



Fig. 13. — The tracheal sacs supplied by the anterior thoracic spiracle {a.lh.). 

 In this figure the tracheal sacs supplied by the posterior thoracic spiracle and 

 the sterno-dorsales muscles of the left side have been removed. The left side 

 of the head and proboscis have also been removed. The first abdominal seg- 

 ment has been removed to show the large abdominal air sacs {ab.s.) and an 

 abdominal trachea which is supplied by the second abdominal spiracle {a.sp.). 



u.c.s. Anterior cephalic sac. a.v.s. Anterior ventral thoracic sac. c.tr. 

 Cervical tracheal duct. d.c. Dorsal cephalic sac. do. Dorsales muscles. 

 //. Haustellum. l.ir.s. Longitudinal tracheal sac. p.c.s. Posterior cephalic 

 tracheal sacs, p.v.s. Posterior ventral thoracic sac. p.op. Periopticon. 

 lios. Rostrum, v.c.s. Ventral cephalic sac. 



Fig. 14. — Thoracic compound ganglion after the removal of the cortex. 

 Seen from the ventral side. This and Fig. 12 were drawn from models re- 

 constructed from sections. 



Pr.G., Ms.G., Mt.G. Pro-, meso-, and meta-thoracic ganglia. A.G. Abdo- 

 minal ganglion. Other lettering as in Fig. IL 



Fig. 15. — The tracheal sacs supplied by the posterior thoracic spiracle. 



