MANUAL OF NATURAL HISTORY. 311 



incurved hooks; dorsum convex, produced 

 in the middle into a long straight styliform 

 process. 



ANNELIDS. 



The Red-blooded Worms, as the Annelids are fre- 

 quently termed, are elongated animals with jointed 

 bodies, and are either aquatic or terrestrial in their 

 habits. They are at once known from other Classes 

 of the Annulosa by never having jointed limbs, 

 these being represented by simple bristles. There 

 are regular tentacles in some genera, the head is 

 usually furnished with eyes, and the mouth is often 

 provided with jaws ; the most curious character 

 about them, however, is the colour of their blood, 

 which is red, an unusual circumstance among in- 

 vertebrate animals. 



Among the Annelids we find the Tube-worms 

 (Tubicola), which construct for themselves cover- 

 ings either entirely calcareous and fixed to the 

 surface of stones, as the Serpulce, or formed of 

 agglutinated fragments jointed together by an 

 insoluble cement, as the Terebellce; the tufts 

 of gills attached to the front part of the bodies of 

 these animals when fully expanded are adorned with 

 brilliant colours, and form beautiful fans and plumes 

 protruding from the mouth of the shell ; some- 

 times one of the tentacles of the head is formed 

 into a curious funnel-shaped operculum, which pro- 

 tects the creature from injury when it has with- 



