162 



ZOOLOGY 



Fig. loll. — All annelid (Eunice). 

 Anterior and posterior ends of 

 the body only ; dorsal \ievi. fa, 

 unpaired feeler; fp, paired feeler; 

 a, eyes ; fc, feeler-cirri ; A", gills ; 

 ■pc, dorsal parapodia ; 7), para- 

 podia ; ac, anal cirri. -VfterLang. 



ing certain parts of the body-wall 

 and expanding others on the same 

 side of the body at the same time, 

 and this is possible only with short 

 muscles. When the muscles run 

 continuously from head to tail, as 

 in the " vinegar eel," the body 

 flops from one side to the other as 

 a whole. 



The segmentation of the body 

 has led to important consequences. 

 Each segment contains not only 

 its own muscles, but a pair of ap- 

 pendages that are moved by the 

 muscles, nerves to control the 

 muscles, blood-vessels to supply 

 them with food, and a pair of 

 excretorjr organs to carry off waste 

 products. Each segment is, in- 

 deed, a nearl_y complete organism, 

 and, consequentl}^, even small 

 parts of an annelid cut out from 

 the rest of the body may live a 

 long time and even regenerate the 

 lost head and tail. 



The head of the annelid is simple 

 in the earthworm and the other 

 herbivorous forms ; but in Nereis 

 and the other carnivorous species 

 (Fig. 160) it gains a great size 

 and is jDrovided with various sense 



