40 
CHARLES BADHAM. 
somite the pair of branches (Np. b.) leading to the nepliridiopores 
( Np .). D. 1. Dorsal lacuna. D. v. Dorsal vessel. L. n. c. Lateral 
nephridial canal. N. p. Nepliridiopore. Np. b. Duct leading to 
nephridiopore. T. Testis. V. 1. Yentral lacuna. V. ne. Ventral nerve 
cord. V.v. Yentral vessel. 
Fig. 8. — Diagram in relief of the Lacuna System, viewed from the 
dorsal surface, in a somite of the testicular region of the body. The 
dorsal lacuna ( D.l .) is shown containing the dorsal vessel (D.v.). In 
the ventral lacuna (V. 1.) are the ventral nerve cord (F ne.) and ventral 
vessel (V.v.). The dorsal and ventral parts of the segmental lacuna 
of either side of the somite are seen to junction laterally, and after 
bifurcating to join up with branches from the preceding and succeeding 
segmental lacuna) of the same side. The segmental lacuna opens into 
the contractile lacuna in two places in each somite. The contractile 
lacuna receives in each somite three capillaries dorsally on either side. 
Cap. 1. Capillaries opening into contractile lacuna. C. 1. Contractile 
lacuna. D. 1. Dorsal lacuna. I). v. Dorsal blood-vessel. S. 1. Segmental 
lacuna. V.l. Yentral lacuna. V.ne. Yentral nerve cord. V.v. Yentral 
vessel. 
Fig. 9. — Drawing of horizontal section through the testicular region 
of the body showing the character of the contractile lucana (C.l.) and 
the branches of the segmental lacuna ( S.l .) leading to it. In one 
place a branch opens into the contractile lacuna and the opening is 
guarded by sphincter muscle fibres (S. m.f). The large unicellular 
lateral glands ( L . gl.) are shown, and the clitellar glands medial to the 
contractile lacuna. C. 1. Contractile lacuna. Cl. gl. Clitellar glands. 
L. gl. Unicellular lateral glands. (S.m.f.) Sphincter muscle fibres. 
S. 1. Segmental lacuna. 
Fig. 10. — Drawing of a transverse section through the dorsal blood- 
vessel and dorsal lacuna in the testicular region of the body, showing 
the dorsal and ventral septa (Sep. d., Sep. v.). The nuclei of the 
epithelial cells of the dorsal vessel bulge into the dorsal lacuna. D. v. 
Dorsal vessel. D. 1. Dorsal lacuna. Epi. nu. Nucleus of epithelial 
cell. Sep.d. Dorsal septum. Sep.v. Yentral septum. 
Fig. 11. — Drawing of a section through a valve of the dorsal blood- 
vessel in the testicular region of the body. Usually the valve (VI.) 
is fir-cone shaped and when forced back rests against the sphincter 
muscle fibre (S. m.f.), but sometimes, as shown here, the valve becomes 
broken up into separate cells attached to a common stalk. On con- 
traction of the dorsal vessel several cells of the valve may be forced 
past the spincter, as is shown here. D.v. Dorsal vessel. VI. Yalve. 
S. m.f. Sphincter muscle fibre. 
Fig. 12. — Drawing of a transverse section through the neck region 
