SEGMENTED WORMS— THE ANNELIDS 



177 



tion of the body becomes greatly swollen. As the sexes mingle in an 

 annelid courtship these swollen regions burst open, liberating the sperms 

 and eggs, and fertilization takes place in the open water. The worms 

 then usually die, but in some species the uninjured anterior end may 



Fig. 12.5. Neanthes, the clam worm. Dorsal and ventral views. 



regenerate a new posterior and life continues. In one species of marine 

 annelid, the palolo worm of the South Seas, the posterior end of the 

 animal breaks off and goes swimming to the surface, leaving the an- 

 terior end which begins regeneration of its lost posterior. This repro- 



