8o 



THE EVOLUTION OF MAN. 



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

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

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

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



■TTP 



Fig. 184. — A simple Gliding-worm {Rhabdoccelum): -m, mouth; sd, throat- 

 epithelium ; sm, throat-muscles ; d, stomach-intestine ; nc, kidney ducts ; 

 nm, opening of the kidneys ; au, eye ; na, nose-pit. 



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

 hrain ; au, eye; na, nose-pit; n, nerves; 7), testes; ^, male opening j 

 $) female opening ; e, ovary ; /, ciliated onter-skin. 



