THE BIOLOGY OF AN ANIMAL. 



Besides the lateral vessels from the sub-neural and supra-neural a pair 

 of " ventro-lateral " (-0.Z., Figs. 26 and 27) are given off in each somite from 

 the sub-intestinal to the nephridium, probably receiving from it the blood 

 which originally entered through a branch of the dorso-tegumentary. 



FlG. 27. Nephridia of Lumhricus. A showing the regions of the tube, J3 the vascular 

 supply. /, ZT, III, the three principal loops. 



A. /, funnel; .f, the "narrow tube" 1 ; m.f, middle tube; w.t, wide tube: m.p, mus- 

 cular tube or end-vesicle ; ds, dissepiment. The narrow tube extends from a to y 

 and is ciliated between a and fr, at c, and from d to e. The middle (ciliated) tube 

 extends from g to h , the wide tube from h to fe, where it opens into the muscular 

 part ; ex, external opening. 



B, Letters as before ; d.t, dorso-tegumentary vessel, bringing blood from the dorsal 

 vessel, receiving at s a branch from the body-wall, sending an afferent branch to- 

 the nephridium, and finally joining the sub-neural (S.H); i'-', ventro-lateral vessel 

 carrying the blood from the nephridium to the sub-intestinal or ventral vessel 

 (s.t) ; i\?i, ventral nerve-cord. (After Benham ; the direction of the blood-cur- 

 rents according to Bourne.) 



Excretory System. It is the office of the excretory system to- 

 remove from the body proper the waste matters ultimately re- 



