TRANSACTIONS OF SECTION D. 599 



13. The Habits of Tube-building Worms. By Arnold T. Watson. 



The fact has long been known to naturalists that many animals, ranging from 

 the foraminifera, through the bristle-worms (or polychaeta), rotifera, Crustacea, 

 insects, and mollusca, up to fishes, birds, and certain quadrupeds, are in the habit 

 of building or forming structures (composed of the material with which they are 

 surrounded), either for the protection of their bodies against the attack of enemies, 

 or for some other purpose, such as a temporary home for the reception of their 

 young. 



As regards the larger and higher animals the methods by which these struc- 

 tures are produced are fairly well known, but this is not so in the case of the lower 

 forms. 



Amongst the latter, probably no group affords more interesting examples of 

 structural workmanship than the polychsete worms. These worms, with very 

 few exceptions, are marine ; most diverse in form, and some of them as charming 

 and attractive as the most beautiful flowers. Some of the tube-building worms 

 are sedentary, their tubes being fixtures to the spot, but others travel about freely 

 through the sand or on its surface. 



In all cases special means are provided for respiration, which is mainly effected 

 through the skin, the water being drawn through the tube by a peristaltic pump- 

 ing or a waving action of the body of the worm. As an example of the flower- 

 like form, the lecturer described Sabella from his personal observations, and [by 

 means of lantern-slides and a cardboard model] explained its method of tube- 

 formation, the material being collected by the so-called branchial tentacles and 

 applied, by the collar lobes, as a coating on the outside of a secreted tube. 



As a guard against the intrusion of an enemy, the mouth of the tube usually 

 collapses, but in one rock-boring species of this family the end of the tube rolls up 

 like the frond of a fern. As an instance of a different form of sedentary worm, 

 the method was fully described by which Terebella builds with sand, shells, or 

 gravel the tubes so common on our shores, the free ends of which are terminated 

 by a wonderful arborescent arrangement constructed by the worm with single 

 grains of sand or other material which it finds suitable. 



After a brief reference to the immense honeycombed masses with which 

 colonies of Sabellaria in many places bind together sandy shores, and to the cal- 

 careous tubes formed by the Serpulids, the lecturer passed on to the mud-eating 

 errant worms. It is by a worm of this group, the golden-combed Pectinaria, 

 that the most beautiful masonry is produced. 



The material for formation of these well-known conical sand-tubes is evidently 

 selected with the greatest care and most conscientiously fitted into appropriate 

 positions, no superfluous cement being used to make up for bad workmanship. 

 The second example of this group was Oweniajilifoi-mis, a worm which constructs 

 a flexible tube by attaching, in an imbricated manner, the flat sand-grains or 

 fragments of shell to a membranous tube secreted by special glands. In this tube, 

 as in a coat of mail, the worm burrows through the sand, its hold on the tube 

 being ensured by an immense number of uncini, or hooks, arranged in bands 

 round the body. A most interesting fact in connection with this worm is that 

 the imbricated formation of the tube has been rendered possible by an extra- 

 ordinary modification of the structure of the animal itself. The third group 

 comprised worms regarded as carnivorous from the fact that they are provided 

 with formidable jaws ; these were exemplified by Panthalis cerstedi and certain 

 onuphid worms, all deep-sea forms. Panthalis constructs a massive tube by 

 weaving together cobweb-like threads supplied by the glands of the feet, and 

 mingling therewith mud obtained from the sea bottom. The onuphids described 

 formed scabbard-like tubes of shells or flat stones, or secreted tubes of a horny, 

 transparent material, in which they creep about the bed of the sea. The tubes 

 are open at both ends, but the worms defend themselves with considerable 

 mechanical skill against the attacks of enemies by constructing membranous 

 ihternal valves at each end of the tube (on the principle of the valves in a vein), 

 which, by inrush of the sea water, are closed automatically on retreat of the 

 inmate. 



