TEREBELLIDS. 105 



in the " Drift-Larvse " it was probably pelagic. Those captured in British waters have 

 hitherto had transparent tubes of secretion. 



Erik Nordenskiold l (1901) gives a careful account, with a plate, of the structure 

 of a larval Terebellid (Wartelia) which he found at St. Andrews. 



Some remarks on fossil Terebellids comparatively recently (1911) made by 

 Dr. Bather 2 are of special interest, since certain tubes originally described by W. Davies 

 are partly composed of the bones and scales of various species of fishes — a feature 

 apparently unknown in living forms, though the composition of the tubes is sufficiently 

 varied. The slender fin-rays are arranged in the long axis of the tubes, just as the 

 linear leaves of the pines are in the Japanese forms of the " Challenger " and in those 

 from the cretaceous beds of Bohemia. Tubes composed entirely of secretion occur both 

 in these fossil types and now. Whilst tubes of the same species are generally speaking 

 similar, it may happen that a widely distributed species removed from its ordinary 

 surroundings in sand to a muddy bottom in deep water is compelled to fashion its tube 

 of neatly arranged sponge- spicules placed transversely. 



Terebellids abound on sandy shores, especially beyond low water, though many 

 fine species occur between tide-marks and in fissures of rocks. Others inhabit deep 

 water, even to great depths, viz., 2750 fathoms. They are strictly tubicolar, though 

 some, as Nicolea venustula, when free were found by Michaelsen to swim freely, and 

 others do the same. In size they range from 40 cm. downward, and their colours are 

 often both varied and bright, the rich red branchise, the roseate tentacles and the 

 speckled body of certain forms being noteworthy. 



Young Terebellids are abundant in the pelagic condition, especially in the bottom 

 tow-nets from May to September, in their transparent tubes shaped somewhat like a 

 post-horn, and they are accompanied during the warmer months by young examples 

 of Clione. A post-larval Terebellid, Amphitrite pr&cox, of De St. Joseph, possesses long 

 bristles like an epitokous form, and develops ova. 



Their food consists of the forms in their immediate neighbourhood, such as 

 Diatoms, Foraminifera, Ptadiolarians, spicules of sponges, and fragments of Polyzoa, 

 molluscs and hydroids. 



As mentioned, external crustacean parasites (e. g. Terebellicola) are rarely present, 

 but Distomes occur anteriorly in the gut (De St. Joseph), a Nematode (Lyorhynchus, 

 Bud.) in Loimia medusa, and another and a Tetrarhynch in Polycirrus, whilst Protozoan 

 parasites, such as Cothurnia, Rhabdostyla and Ophryodendron are more common. 



Terebellids are by no means sluggish animals. When freed from their tubes they 

 swim actively with a quick, wriggling movement, the tentacles being in front ; the jerks 

 are rapid and vigorous, and they make considerable progress. 



The tubes of the Terebellids comprise many and varied structures, from the fringed 

 anterior processes of Lanice conchilega to the remarkable spinose tube of the " Challenger " 

 species, or the more delicately hirsute tube of the British Terebella B (Plate CXIX, fig. 7). 

 The compact spiral tube of Caullery's Streblosoma longiremis is another curious form, 



1 f Ofversigt Finsk. Vet.-Soc. Forhandl./ B. xliii. 



* u Upper Cretaceous Terebelloids from England/' ' G-eol. Mag./ dec. v, vol. viii, p. 481, pi. xxiv. 



183 



