HALF AN HOUR WITH SEA-WORMS. 79 



sands, literally eating its way along, and passing 

 the excreted sands out ; after the organic matter with 

 which they were charged has been extracted in its 

 passage through the worm's body. When you 

 examine it carefully you perceive that it has no eyes 

 or jaws, as some of the " errant " sea-worms have. 

 It breathes by means of thirteen pairs of branchiae, 

 which are arranged on each side. The digestive 

 system of the true " Errantia," of which we may 

 take the common Nereis as an example, is very 

 peculiar. They possess a mouth, horny jaws, gullet, 

 stomach, intestines, and anus, so that it will be 

 perceived they are not by far such lowly organised 

 creatures as might at first be supposed. Indeed, the 

 worms as a class (Anarthropoda) stand relatively 

 higher than the anemones, sea-urchins, &c., on 

 account of their more complex specialization. In 

 this respect, therefore, the rule laid down by Yon 

 Baer holds good, that " the progress of development 

 is from the general to the special." The circulating 

 apparatus in these worms consists of a system of 

 vessels with contractile walls, the vessels being 

 filled sometimes with red, and at others with a 

 greenish fluid. This is termed in scientific language 

 the " pseudo-haemal system." Eespiration is carried 

 on either by the general surface of the body or by 

 means of gills or branchiae set apart for the purpose. 

 The nervous system is gangliated, and well deve- 

 loped. Although most of them are furnished with 

 what look very much like antennae, a little observa- 



