Chiefly living below tlie surface of the 



soil (often crawling on the surface after 



rain, &c.), or among rotting timber or 



other vegetation. Others, of small size, 



in fresh water, or in mud at the bottom 



of ponds and streams. 



(2) PoLYCHJiTA (see Figs. 8, 9 and 16). 



Each segment bears generally a fin-like 



expansion on each side, from which 



bristles project fanwise. These expansions 



may be wanting, or confined to the front 



end of the body, in forms whicli inhabit 



tubes. 



Marine. Some live under stones, or 



buried in sand at low-water mark ; many 



in tubes of their own construction, at- 

 tached to solid 

 objects under water. 

 The tube's are of very 

 . various appearance, 

 some being hard 

 and chalky, others 

 covered with sand- 

 grains, bits of shells, 

 seaweed, &c., others quite transparent. 



Many of the tube-living worms (see Fig. 9) 

 have a flower-like crown of feathery "gills" 

 on the head, which can be protruded from 

 the opening of the tube. 



A few Polychaetes lead an entirely free- 

 swimming life at the surface. 



Certain forms, rather unlike the ordinary 

 conception of a " w^orm," are included in 

 this group (Polychaeta) — such as the Poly- 

 noids, some of which are of woodlouse- 

 like shape and appearance; and Aphrodite 

 (" Sea-mouse ") and its relatives, which 

 are thick-set animals covered with strong 

 bristles and beautifully iridescent hairs (see 

 Fig. 16). 



Figure 7. 

 The " head " end of a 

 typical Echinorhynchus. 



frreatly magnified, showing 

 the eyhndrieal probo!<eis 

 covered with hooks. 

 [ACANTHOCEPIIALA.] 



FIGUEE 



An example of a 

 free-living Polyehsete 

 worm, Lepidasthenia 

 ilegaiu, slightly en- 

 larged, showing the 

 characteristic paired 

 appendages. [Ch.E- 



TO POD A.] 



G. GEPHYREA (see Fig. 10). Marine 

 forms, usually with a simple distended sac-like 

 body, which shows no external traces of seg- 

 mentation. Sometimes a crown of short ten- 

 tacles may be seen expanded at one end. The 

 viscera are enclosed in a spacious body-cavit}". 



