618 



ARTICULATA. 



Tlio curious little spiral shells, often seen upon the fronds of sea-weeds, are formed by an animal 

 lieh)iii,'iiig to this fiiiiiily, the Sj>lrorbis. 



The Jlermclitdce, some of wliich live amoiii; tlie oyster-beds, and often do much miscliief by 

 the increase i>f thoir masses of tubes, also belonj^ to this order. 



EAKTII-WOUMS. 



OIIDER 3. SCOLECINA. 



Of this order deriviii'^ its name from Skolex, a worm, we have well known examples in the 



EartJi- Worms common in gardens and fields. The 

 bodies of these animals are of a cylindrical forni, 

 somewhat pointed at the anterior extremity, and 

 usually a little flattened at the tail. The skin is 

 tough, and divided into numerous segments by trans- 

 verse wrinkles, and the organs of motion are reduced 

 to the form of a double row of bristles, running down 

 the lower surface of the body, which, instead of being 

 placed, as in the preceding orders, upon prominent 

 lobes of the skin, are usually capable of being re- 

 tracted Avithin small hollows when not in use. The 

 mouth is unarmed, and the intestine runs straight 

 through the body. The blood is red. Like the 

 leeches, these worms are furnished with ciliated 

 _-. canals, which have been supposed to serve as organs 

 Eg^= of respiration ; but their real destination appears to 

 ^Z be still uncertain. Like the leeches, also, they are all 

 hermaphrodites. 



This order contains two families — the Lumhricidce 

 ~ or Earth- Worms, and the JVaMidce. The former are 



too well known to require extended description ; they 

 possess no distinct head, and are quite destitute of 

 eyes : their bristles are hooked, and placed in little tufts in pits on the lower surface, whence 

 they can be exserted when the animal requires their assistance. They live in holes in moist earth, 

 and are said to be predaceous animals, although popular belief charges them with the destruction 

 of the roots of plants. It is generally supposed that the earth-worm may be propagated by divi- 

 sion ; but this does not seem to be the case. It is said, however, that if it be divided across 

 the middle, the part bearing the head will develop a new tail, although the tail part will soon die ; 

 and that, if the head be cut off, the body will form a new head ; but it appears that both portions 

 never survive this mutilation. 



The power of reproduction of lost parts seems really to exist in the jVaididce ; these also 



y^ propagate by a kind of gemmation, 

 one seeming to grow out of the 

 other, as represented in the an- 

 nexed engraving. Three young 

 ones are sometimes seen attached 

 ((\ to and growing upon the mo- 



ther, at the same time. It ap- 

 pears, however, that the tail of 

 the original Nais becomes actu- 

 ally the tail of its offspring, by which means, as Jones remarks, " this part of the animal may 

 be said to enjoy a kind of immunity from death." These animals live principally in the mud of 

 fresh-water ponds and rivers. In their form they resemble the common earth-worm ; but their 

 bodies are furnished, besides the ventral bundles of bristles, with a series of long spines on 

 each side. They generally have two distinct eyes, and the mouth is sometimes armed with a I 

 long proboscis. 



