192 MICROSCOPY FOR BEGINNERS. 



beginner, the rows then appearing to be eight, with 

 two spines in each cluster, or four rows with clusters 

 of four spines each. However, if the beginner will 

 examine the front half of the dividing worm, and be 

 guided by the podal spines there, he will have little 

 trouble in recognizing Lumbriculus. 



5. DERO (Fig. 137). 



The posterior extremity is broad and funnel-like, its 

 upper plane often being oblique. It is finely ciliated, 

 as are the finger-like projections and the internal sur- 

 face of the posterior part of the intestine, which is 

 connected with it and forms a portion of it. The cilia 

 produce currents over these parts which are supposed 

 to absorb the oxygen for purposes of respiration. The 

 finger-like processes vary in number from 

 two to eight. They can be elongated or 

 drawn back into the funnel, which can also 

 be retracted and almost closed. When ex- 

 rior extremity tended they may be much longer than the 



funnel -like termination of the body, or 

 they may not reach to its margins. The blood is 

 red. The podal spines vary from three to five in each 

 cluster. 



These worms are often found on the sides of the col- 

 lecting-bottle after it has been standing for some time. 

 They usually bury themselves in the mud, with the pos- 

 terior part of the body and the expanded funnel-like re- 

 gion protruded from small mud-chimneys of their own 



