So 



THE EVOLUTIOX OF MAN 



a pair of simple kidney-canals ( " excretory organs " ), in 

 the form of two long, thin, glandular tubes, which traverse 

 the right and left sides of the intestine and open at the 

 hinder end of the body (Fig. 184, nm). We found that the 



■w> 



Fig. 184. — A simple Gliding-worm (Rhabdocoslum): w, mouth; sd, throat- 

 epithelium ; S7n, throat-muscles ; d, stomach-intestine ; 7ic, kidney ducts ; 

 nm, opening of the kidneys ; an, eye ; 7ia, nose-pit. 



Fig. 185. — The same Gliding-worm, showing the remaining organs : g, 

 brain; au, eye; na, nose-pit; n, nerves; h, testes; ^, male opening j 

 ?> female opening j e, ovary ; /, ciliated outer-skin. 



