ANARTHROPODA. 



123 



are comparatively few in number, hence the modern name of 

 the order (Gr. oligos, few ; and chaite, a bristle). In the com- 

 mon earth-worm (Lumbricus terrestris) the body is cylindrical, 

 attenuated at both ends, and furnished with eight rows of 

 locomotive bristles. The mouth is destitute of teeth, and 

 opens into a gullet which leads to a muscular crop, succeeded 

 by a second muscular dilatation or gizzard. The intestine is 

 continued straight to the anus, and is constricted in its course 

 by numerous transverse partitions springing from the walls 

 of the body-cavity. The pseudo-haemal system is well de- 

 veloped ; and there exists in even greater numbers than in 

 the leeches the series of segmental organs, or lateral pouches, 

 which open externally by pores. The JtfdididoB are chiefly 

 noticeable on account of their power of producing fresh indi- 

 viduals by a process of budding before they attain sexual 

 maturity. One of the commonest of them is a little worm 

 which occurs abundantly in many pools and streams (Tubifex 

 rivulorum), and which exhibits a fine red color, owing to the 

 pseudo-haemal system being visible through the transparent 

 integument. 



OKDEE III. TUBICOLA. The Annelides included in this 

 group derive their name from the 

 fact that they have the power of 

 protecting themselves by means of 

 tubes (Lat. tuba, a tube; and colo t 

 I inhabit). In some cases (Fig. 

 48) the tube is composed of car- 

 bonate of lime, and is a genuine 

 secretion from the body. In all 

 the Tubicola the respiratory organs 

 are in the form of branched fila- 

 mentous external gills, in which 

 the fluid of the pseudo-haemal sys- 

 tem is subjected to the action of 

 the outer water. They are, there- 

 fore, " branchiate " Annelides. As FIG. 48. TWcoia, 

 they live in tubes, however, and 

 do not voluntarily expose more 

 than the anterior end of the body, 

 the branchiae are all placed on or near the head. The filaments 

 of which the gills are composed (Fig. 48, a) are richly ciliated, 

 and, as the pseudo-haemal fluid is usually red, they have gen- 

 erally a beautiful scarlet color. 



a Serpuia con- 



