16 Prof. W. C. :M 'In tosh on certain 



tube or liome secrete otlier than the transparent chitinou? 

 material for a lininj^, for fixing the foreign bodies, or for 

 forming the entire structure. In all the succeeding groups a 

 calcareous substance is poured out, which consolidates into a 

 dense shelly tube for the iidiabitant, and, moreover, in at 

 least one instance the agglutinated tubes form considerable 

 masses, so as to resemble certain kinds of coral ; indeed, 

 those unacquainted with the group often relegate tliera to the 

 latter. As Dr. Williams observes*: — " The lime of which the 

 tubes are built is held in solution by the mucus provided by 

 the cutaneous glands. It is adjusted in the fluid form, and 

 moulded by a])propriate tools into the required shape; it then 

 solidifies under water like ' Aberthaw lime.' " 



Conspicuous by its relative size, the elongation of the 

 opaque-white tube, and the absence of a ])lug or operculum 

 for closing the free end, Protula affects the deeper water in 

 the northern seas. The pure white tube is here and there 

 wrinkled and more or less straight, and the aperture is 

 smooth. It tapers from the larger anterior region to the 

 posterior end, the former being the home of tiie full-grown 

 annelid. 



From deep water also come the remarkable coral-like 

 masses already alluded to, and formed by the tubes of 

 Filigrantty an annelid likewise devoid of a lid or operculum 

 for closing its shelly tunnel. The slender tubes are united 

 into irregular bundles, often with spaces between, and eacli is 

 inhabited by its eight-gilled architect. 



A white tube tinted anteriorly of a roseate hue and with a 

 trumpet-like aperture characterizes the home of Serpula wr- 

 micularisj which is attached to shells and stones from deep 

 water. Occasionally three or four trumpet-shajied tiers occur 

 in front, Avhere additions have been made to the tube after 

 the first wide rim has been formed. The annelid closes the 

 a]K'rture anteriorly by a plug, the surface of which is marked 

 by a beautifully radiate series of grooves. The tubes oi a 

 species {S. nar con ens lit) obtained by the 'Challenger' in the 

 Strait of Magellan show many prominent rings from the 

 widely ex])anded a})ertures, showing tiiat growth had appa- 

 rently taken place by fits and starts ; and a similar condition 

 is mentioned by Cla]1ar^de in <S'. crater from Naples. The 

 tubes of the s})ecies from the Strait of ^Magellan form free 

 masses. An allied, tlumgh smaller tube, but without the 

 truni])et-like anterior end, is secreted h\ Hiidroides norve(jica ; 

 these two genera illustrating the series with eireidar tubes o( 

 considerable length. 



* OjK cit. ji. i>0.>. 



