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POLYCHAETA 



CHAT. 



for particles of sand, etc. ; each tentacle is grooved along its 

 ventral surface, and the particle is conveyed along the furrow to 

 the mouth. These particles are actually taken into the mouth, 

 and mixed with some sort of secretion ; on ejection again, each 

 particle is placed by another tentacle in its position at the 

 edge of the tube, and by means of its lower 

 lip the Terebellid works it into place. 1 



But whereas the greater number of tubi- 

 colous worms make use of adventitious mate- 

 rial wherewith to strengthen the wall of 

 their tube, the Serpulidae secrete carbonate 

 of lime from their tube-glands, and mould 

 a tube of this substance. Amongst the 

 Eunicidae the secreted substance is of itself 

 strong enough to protect the animal ; for 

 in Hyalinoecia and species of Eunice the 

 tube consists of a translucent, tough, parch- 

 ment-like material. 



Chemical analysis has been employed in 

 a few cases to determine the substance com- 

 posing the tube. In the case of Hyalinoecia 

 (sometimes erroneously called Onuphis) the 

 material consists of a phosphoric salt con- 

 Fig.155. -Eunice tibiana taining magnesia and a characteristic organic 

 Pourt. x $. The sllDs tance " onuphin " 2 ; in Spirographis, a 

 with the worm (w) Sabellid, the name " spirographin " is given to 

 {rougfoLoflseveTal its s P ecial secretion, whilst in Serpulids the 

 openings. (From organic base of the calcareous tube is "con- 

 SUm ) chiolin." 



The majority of worms are solitary, but there are a few 

 instances of social worms not that there is any co-operation 

 or distribution of labour amongst the individuals, but they 

 merely occur together in quantities ; thus the sandy tubes of 

 Sabellaria may form compact masses of several cubic feet, which, 

 left uncovered by the receding tide, look like rocks upon the 

 shore ; as, for instance, at Paignton and Torquay. Filigrana 

 im/plexa and Serpula uncinata similarly intertwine their calcareous 

 tubes to form masses. 



Watson, Journ. E. Mic. Soc. 1890, p. 685 ; see also Dalyell, loc. cit. ii. p. 195. 

 2 Sohmiedeberg, ML Zool. Stat. Ncapel, iii. 1882, p. 373. 



