2 lo Introduction to A^iimal Morphology. 



raised on unjointed, movable side-processes of the 

 body wall (parapodia*). These bristles are chitinous, 

 striated, full of protoplasm, rarely hollow, calcareous 

 (Euphrosyne) ; they arise in follicles, and muscular 

 fibres are attached to their roots. When the cuticle is 

 hard the young bristles have often deciduous points 

 for piercing their way through the surface. There are 

 variously arranged dermal appendages or cirri, often 

 shield-like [elytrae) and iridescent, or groups of long 

 pillared suckers, as in Pelogenia, somewhat like the 

 ambulacra of an Echinoderm. Nettle-cells, or rod- 

 like bodies resembling them, are found in the tentacles 

 and cirri of Spionidae, Chaetopteridse, Ariciidse, &c. 

 The cirri on the prostomium are thread-like [anfenncB)^ 

 or thick and fleshy [palpi). Those of the peristomium 

 are called tentacles. The tail has generally two long 

 cirri. 



The cuticle is of many layers, soft and thin at the junctions 

 of the zonites. The whole surface is rarely ciliated (Ichthy- 

 diidae). Polyophthalmus and Prionognathus have cilia in 

 bundles. Partial ciliation is common, especially on the ap- 

 pendages (Capitella has two ciliated head-lobes). The 

 cuticular laminae are often striated, the superficial and deep 

 striae crossing at angles of 70° or 90°. Through these layers 

 pass pore canals, which may open on wart-like eminences. 

 The connective cutis is thinner than the cuticle, and contains 

 pigment cells, bacillar corpuscles, and glands, of four kinds — 

 uni-cellular (in Lumbrici) ; mucous, with an epithelial lining, 

 often lobate and numerous, either over the whole surface, 

 along the line of the cirri, or along the notopodia only 

 (Sphserodorum) ; tubular glands in Nereids secrete globular 

 concretions ; calcigerous dorsal glands in Serpulae, which 



* These are rarely bristle-less, never modified into jaws. In higher 

 forms there are two pair on each zonite : two dorsal, one on each side, 

 called Notopodia, and two ventral, Neuropodia. 



