532 BIOLOGY. 



3250. These Worms have also no liver, or at the very 

 best only traces of that organ, by reason of the prepon- 

 derance of the arteries. 



3251. Papillae or sensitive filaments gradually sprout 

 from the external branchial filaments, lie along the sides 

 of the body, and are the prelude of the feet ; as in the 

 Nereides Papillary, Filamentary animals. 



3252. Others of these filaments become horny and 

 appear as setae or bristles, placed somewhat similarly to 

 the above, as in the Earth-worm. 



3253. Mouth and head are more perfectly developed 

 than in the Entozoa. The first can readily expand and 

 contract, frequently protrude the pharynx like a pro- 

 boscis or tube, and not unfrequently has manducatory 

 pincers, like as in Insects. 



3254. On the head there are mostly annulate ten- 

 tacula with muscular fibres, and frequently simple eyes. 



3255. In those species which draw the water itself 

 into the body and use it for the purposes of respiration, 

 the formation of the mouth has risen higher, and the 

 pharynx been provided with maxillae, in number five 

 or ten Echini, Holothuriae. These maxillae form in 

 themselves a peculiar skeleton around the pharynx, which 

 is ranged circularly instead of by pairs. 



3256. The nervous system is directed according to 

 the relations of the tegument and intestine. It forms 

 two ganglionic cords running along the ventral side of 

 the body, and, where it makes with the nerves going to the 

 maxillae a ring around the pharynx, corresponds to the 

 cesophageal nerves or those that sweep around the gullet. 



3257. In reference to the sense of feeling it maybe 

 said, that the Worms were those among the Sensitive 

 animals, which feel by the whole tegument or body. 

 Their body itself is a tentaculum. 



3258. The sexual parts are likewise intestini- and 

 dermiform, not glandular in figure like the ovarium and 

 testis of Mussels and Snails, but tubular, as in the 

 Entozoa. There are usually two oviducts and two 

 seminal tubes to be found. 



