30 



BRANCH VEKMES. 



tunnel. This bringing up from below and depositing on 

 the surface, results in a constant overturning and enrich- 

 ing of the soil. It also undermines, at a rate perhaps 

 of an inch in a dozen years, pieces of stone and other 

 debris, which are thus constantly disappearing from the 

 surface. Its eggs are deposited in the soil and develop 

 directly into Earth-worms. 



ORDER POLYCH/ETA (pol I ke'ta). 



Many of the Marine-worms (Nereis) have the_ append- 

 ages of the sides of each segment greatly enlarged, with 

 expansions which functionize as gills, and with tufts of 

 elongated bristles. The Clam-worm, so named because it 



FIG. 41. 



Ne'ra is pelag'i ca. Clam-worm, a, Male. 6, Female. (Natural size.) 



is often brought to light where these mollusks are being 

 dug, well illustrates such a form. The head is quite dis- 

 tinct, surrounded with long feeling organs, the an/a/t/ti- 

 (an ten'ne), and bears one or more pair of eyes. From 

 the mouth can be protruded a long proboscis, which is 

 armed with terminal teeth and secures the animal's prey, 

 finally drawing it into the stomach. With such well- 

 developed and specialized organs, we should expect to 

 find the Clam-worm an active animal, and such it is. 

 At night, it is -known to leave its submarine and sub- 



