in] OTHER DEFINITIONS 73 



That is its structure when young : at the close of 



n 



Fig. 5. Diagram of a Pilidium with young Nemertine enclosed. 

 &, band of special long cilia; e, envelope enclosing the worm ; 

 w, mouth ; n, the young worm ; s, stomach. (Magnified.) 



its life, however, it is seen to contain a darker some- 

 thing within itself, and this something on closer 



