EXPLANATION OF PLATES. 



PLATE VI. 



Fio. 1.— Ventral seta detached, x 120. 



Fig. 2. — Ventral seta in its sac, with problematical gland (?) just 

 behind its tip, and terminal portion of duct of nephridium in front. 

 X 192. 



Fig. 3.— Valves of dorsal vessel, x 328, 



Fig. 4. — Diagram showing course of lateral vascular arches, and 

 position of valves, x 36. 



Fig. 5.— Ventral nerve cord in one somite, with ventral organ 

 and lateral nerves. The figure shows also the thick longitudinal ven- 

 tral muscle, the thin circular muscle layer, the hypodermis, and the 

 cuticle. X 200. 



PLATE VII. 



Fig. 6.— Transverse section of nerve cord and ventral organ from 

 anterior part of body, showing also portion of ventral longitudinal 

 muscle, circular muscle layer, hypodermis, and cuticle, x 192. 



Fig. 7.— Same as Fig. 6, but from central part of body, x 192, 



Fig. 8. — Ciliated funnel of nephridium, and portion of anterior 

 lobe of fatty body, with septum intervening, X 328, 



Fig. 9.— Front view of ciliated funnel of nephridium, x 328. 



Fig, 10.— Diagram showing form and position of fatty bodies, 

 X43, 



Fig. 11. — Transverse section of alimentary canal and dorsal and 

 ventral vessels, a short distance behind oesophagus. The outer cells 

 form the chlorogon layer, x 192. 



PLATE VIII. 



Fig. 12.— Same as Fig. 11, but from central part of body, x 192. 

 Fig. 13,— Portion of wall of alimentary canal, x 328, 

 Fig. 14,— Gregarinffi,— one attached to wall of intestine, x 192, 

 Fig, 15,— Single-celled parasites from cd^lom, x 328. 



