CHAPTER X 



The Beard Worms 



(Pliyl/un Pogoijophora) 



A, 



.MONG the most astonishing discoveries made 

 with deep-sea dredges in the twentieth century was 

 the finding of this assemblage of tube-building, 

 wormlike creatures, for they live their solitary lives 

 and reach a length of as much as 13 inches, a diame- 

 ter to 'ii, of an inch, with no trace whatever of a 

 digestive system — a condition unique among free- 

 living many-celled animals. 



The body of one of these long and exceedingly 

 slender worms shows a subdivision into three regions: 

 a proboscis bearing from one to more than two hun- 

 dred tentacles on its underside; a collar-like enlarge- 

 ment; and a long posterior body whose final third 

 may be marked oft' into a large number of successive 

 rings by rows of raised adhesive areas. With these a 

 beard worm clings to the slender, close-fitting tube it 

 has secreted in the bottom mud. The tube consists 

 of a series of rings or slightly funnel-shaped pieces 



composed of animal cellulose — the material found in 

 the tunic of a sea squirt. 



Enough is known about the embryos of beard 

 worms to show that they too lack a digestive tract 

 and consequently cannot be assumed to store enough 

 food to last for the lifetime of the worm. Instead, a 

 beard worm seemingly must depend upon decompo- 

 sition products diffusing to it from bacterial action in 

 the surrounding abyssal water, or must be able to 

 control digestion outside its body in an enclosed space 

 of some kind. 



In searching for an enclosed space of this descrip- 

 tion, scientists have looked suspiciously at the slen- 

 der cavity within the spiral of the single tentacle in 

 species of SibogUmtm, or between the outstretched 

 parallel tentacles of worms in other genera. 



In Gulathealiniiin somewhat more than one hun- 

 dred tentacles lie side by side, anterior to the worm 

 in its tube. In Spirobruchia the number may be more 

 than two hundred. In Lainellisabelki the tentacles 

 form a watertight cylinder for most of their length, 

 and only the tips are free. Into this cylinder extend 

 short lateral projections comparable to those found 

 on one or both sides of the tentacles in all other 

 beard worms. 



The tentacles do have thin walls and an extension 

 of the closed circulatory system. But so far, no gland 

 cells have been discovered that could secrete diges- 

 tive ferments, and the secret of the beard worms' 

 nourishment remains an intriguing enigma. 



Of the twenty-four known species of beard worms, 

 thirteen have been found only at great depths be- 

 tween Kamchatka and the islands just north of Ja- 

 pan. Four more appear to be limited to somewhat 

 shallower waters in the same general region. Sibogli- 

 nuiu has been dredged from the Skagerak off the 

 Norwegian coast at depths from 500 to 2000 feet, 

 from British waters, and from tropical western parts 

 of the Pacific. The last is the only known home of 

 Galcithealiiuim. Lanielllsabella has been recovered 

 from close to ten thousand feet below the surface in 

 both the Okhotsk Sea and the Gulf of Panama. 



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