SOME AQUATIC WORMS, ETC. 205 



At a short distance from the attached end of each pair is 

 often to be found anothel: pair which are small and may 

 be overlooked on the front of the body when the worm 

 is not dividing transversely. When it is undergoing 

 transverse fission the posterior part may be so well 

 supplied with these small secondary podal spines that 

 their number and arrangement may confuse the be- 

 ginner, 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 observer will ex- 

 amine 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. 150). 



The posterior extremity is broad and funnel-like, its 

 upper plane often laeihg oblique. Its inner surface is 

 finely ciliated, as are the finger-like 

 projections and the internal surface of 

 the posterior part of the intestine, 

 which is connected with it and forms a 

 portion of it. The cilia produce cur- ii/l (lil 

 rents over these parts which are sup- LTV"^ 



posed to absorb the oxygen for pur- ^'fremrt3ro^°fDlro.''''" 

 poses 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 extended 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 



