CLASS VERMES: ORDER ANKULATA. 



237 



animal is withdrawn into the tube. Other worms nearly 

 allied to Serpula form a tube by cementing together grains 

 of sand and bits of broken shells. 



The LumbricidsB (Common Earth or Angle-worms) are 

 wanting in gills, but minute apertures on the sides com- 

 municate with internal respiratory sacs, on the walls of 

 Which the blood circulates for aeration. Tiny spines directed 

 backward enable the worm to force its way through the 



Mg.ms. 



Mg. U)S. 



a. LumMem terrestris. Angle or Earth- 

 worm, b. Anterior segments magni- Mrddo tnecllcinBlis, Tjeecli, Europe. 

 fled, showing bristles directed back- 

 ward; 0. Egg, enclosing two young; earth. Digesting the organic 

 d. Escape »/ young fi-om egg. ^^^^^^ .^ ^^^ ^.^^ .^ ^^^^^ ^^^ 



rejected "worm-casts "are of service in the garden, and often 

 cover barren tracts with a layer of productive mould. It is 

 oviparous — a single egg frequently containing two embryos. 



