THK SERTULARID.K. 



25 



A careful study "I (lie matter of reduplication here referred t<> and the renewal n!' the 

 hydranth has been made l>v Professor Levinsen, ami the iv-ult- embodied in a short lint important 

 ]>a|ier. < )in Fornvelseii at' Ernseringsindividerne lios Hydroiderne.' The paper is written in 

 Norwegian, but a condensed sumtnarv of the conclusions arrived at is found in Latin at the end 

 of the paper. The following presents l'rofe.-.-or I,,.y jnscii's conclusions so far as the Sertnlarida' 

 are eoneenied: 



In Hei'lii/uriitlix ct in innltis ' 'iiiii/i<tini/,irii,lis ct ('iiiii/niiiiiliiriiiix i_'iMiima ii"\a extra h vilrut lin-am antecedentem 

 pnuTrscit rt M-rretiii cliilinru extra ni:in;iiiciii Inijus liy<ln>tlnv;i- extrnsa nmam niaru'iiiciii vi-1 aperturam let in 

 -pi-i-ii-lius iipriviilifrris cliani nprrriilinii imviiin I furinat. 



Opereula of almost every type 1 found ammiy the sertularians seem to lie reduplicated, a- is 

 illustrated in liu-. 7' > 7M. 



Certain species of .V, rtuliir'm. 'I'liitiiirin, and St/iif/m-iiim are rliararteri/ed by the fact thai 

 the distal portion of ihe bydrothecsB is produced into a verv thin collapsible tulie. wliich is 

 usuallv of very indefinite shape in preserved specimens. It is seldom that they are of sutlicient 

 consistency to preserve their shape after the hydranth has retracted, and they are for this reason 

 very unsatisfactory structures to study. in SertvlcMna //n///,/'/, for instance, there is such a tulie 



BEDUri.ll-ATlilX OK MAlUilN AST) OPKHri'LUM. 



Fit,'. 7U. l 



Ihr 



ni r*'inn: loiiL:itH'lin;il M-clLon dl mil iti h\ -drothi-iM, liii,'tily uiasiiiti''*!. ^ti 

 Iwii'f ri'illl|ilir:lli'il in:iri;ill .m<l n|,rrc-lllllln 

 Kiu. 71. S:ilnr, shuu JIIL,' sini,'lr n -till! 'lira I L"ll. 

 I [g, T'J. Sillilr s|n-cirs, Itlllcll l.'vs ]M:iL,'nitu'<l, sllii\\'illLr n-illll'l irnti' ill ill" t i|i.-rrl]I inn. 



Fit;. 7;:. 'I'tiui'i, i't t<it<n!<i"t.rnii*. !iiL r lil\ ]aiLL, r niliril. Mi. iwinu rfdu|ili< p :itin!i nl' opcri-uliiin. 



in many cases, and it seems to extend lieyond the opereulum (Plate V. liy. 4). Although the 

 orijrin of this tulie is not definitely known, it seems reasonable to suppose that it is formed, as 

 are all the chitinous part-, of the hydrothecss, 1>\- the excretion from the ectodermal cells of the 

 body wall of the hydranth, and dili'ei'iny from the true hvdrothecal walls in beiiiy ye IT delicate 

 and colla])sible. I have not been able to assure myself of the presence of an operculum at it> 

 distal end. It may be merely an exaggerated form of reduplicated margin, liaviny the same 

 "'diesis, but not beiny completed to the extent of the formation of a new operculum. 



'I'll, l>iiij>/ii'(i,/in. This has been already mentioned incidentally. It occurs in all of the 

 Sertularidse that I have examined, and does not vary yreatly in form, beiny merely a liorixontal 

 circular shelf running around the bottom of the hydrotheca, near the point where its base joins 

 the hydrocaulus, and dividing the hydrothecal cavity from that of the stem. There is thus left a 

 circular opening, through which the saivodal contents of the hydrotheca and stem form a con- 

 nection. 'Phis aperture is usually eccentric in position, beliiy nearer the abcauline than the 

 adcauline side of the hydrothecal base (tiys. 74---7X). The diaphragm is regarded by Alliuan 

 as one of the systematic characters by which the Sertularida- are differentiated from ol her yroups. 

 It is also found, however, in other families of the Calypteroblastea, as the Campanularidse and 

 Campanulinidte, although in the Sertularidee alone it is uniformly eccentric or rather unsym- 



'Sirrtrykaf Viilt'iisikaliflifje .Mnldulelser fra dun iiaturhisturi.ski- Korening i Kjubunluivii, ls:i_'. 



